ppfrc - Construction Materials Research Group (CMRG)

Transcription

REPORT
MECHANICAL PROPERTIES OF
POLYPROPYLENE FIBRE REINFORCED
CONCRETE (PPFRC) AND STRUCTURAL
APPLICATIONS
BY
SHEHNILA FATIMA
June, 2013
DEPARTMENT OF CIVIL ENGINEERING
NED UNIVERSITY OF ENGINEERING AND TECHNOLOGY,
KARACHI, PAKISTAN
i
TABLE OF CONTENTS
TITLE PAGE
Page
i
TABLE OF CONTENTS
ii
LIST OF TABLES
vi
LIST OF FIGURES
vii
LIST OF ACRONYMS
xv
LIST OF NOTATIONS
xvi
ABSTRACT
xvii
ACKNOWLEDGEMENT
xviii
DEDICATION
xix
CHAPTER 1:
INTRODUCTION
1.1 BACKGROUND
1
1.2 OBJECTIVE AND SCOPE
3
1.3 RESEARCH SIGNIFICANCE
4
1.4 METHODOLOGY
4
1.5 ORGANIZATION OF THE THESIS
5
CHAPTER 2:
LITERATURE REVIEW
2.1 INTRODUCTION
6
2.1.1 HISTORICAL EVOLUTION OF FRCC
6
2.1.2 CLASSIFICATION OF FIBRES
6
2.1.3 FIBRILLATED POLYPROPYLENE FIBRE
7
2.1.4 FIBRE REINFORCED CEMENTITIOUS COMPOSITES
8
2.2 FRESH (PLASTIC) PPFRC
9
ii
2.2.1 WORKABILITY
9
2.2.2 EARLY AGE AND PLASTIC SHRINKAGE
2.3 HAREDENED PPFRC
12
21
1.1.1. COMPRESSIVE STRENGTH OF PPFRC
21
1.1.2. TENSILE STRENGTH OF PPFRC
22
1.1.3. FLEXURE STRENGTH PPFRC
23
TABLES
25
FIGURES
27
CHAPTER 3:
EXPERIMENTAL PROGRAM
3.1 GENERAL
30
3.2 MATERIALS
30
3.2.1 CEMENT
30
3.2.2 AGGREGATES
30
3.2.3 WATER
31
3.2.4 FIBER
31
3.2.5 ADMIXTURE
31
3.3 MIX DESIGN
31
3.4 TESTS FOR WORKABILITY OF FRESH PPFRC
32
3.4.1 STANDARD SLUMP TEST (ASTM C143)
32
3.4.2 COMPACTING FACTOR TEST (BS 1811-103)
33
3.4.3 FLOW TABLE (ASTM C1437)
34
3.4.4 J-RING TEST (ASTM1621)
35
3.4.5 L-BOX TEST
35
3.4.6 V-FUNNEL TEST
36
3.5 TESTS FOR PLASTIC SHRINKAGE OF FRESH PPFRC
37
3.6 TESTS FOR MECHANICAL PROPERTIES OF HARDENED PPFRC
38
3.6.1 COMPRESSIVE STRESS-STRAIN CURVE (ASTM C39)
39
3.6.2 SPLITTING TENSILE STRENGTH OF CONCRETE CYLINDERS
(ASTM C496)
39
3.6.3 FLEXURE STRENGTH OF CONCRETE BEAMS (ASTM C78)
40
TABLES
42
FIGURES
46
iii
CHAPTER 4:
RESULTS AND DISCUSSION
4.1 INTRODUCTION
57
4.2 WORKABILITY OF FRESH PPFRC
57
4.3 PLASTIC SHRINKAGE OF FRESH PPFRC
59
4.4 MECHANICAL PROPERTTIES OF HARDENED PPFRC
60
4.4.1 COMPRESSION TEST RESULTS
61
4.4.2 SPLITTING CYLINDER TENSILE TEST RESULTS
62
4.4.3 FLEXURAL (INDIRECT TENSILE) TEST RESULTS
63
TABLES
FIGURES
CHAPTER 5:
65
68
ANALYTICAL WORK
5.1 INTRODUCTION
104
5.2 FRACTIONAL EQUATION FOR COMPRESSIVE STRESS STRAIN CURVE
FOR PPFRC
104
5.3 COMPARISION BETWEEN EXPERIMENTAL RESULTS ANALYTICAL
EXPRESSION
105
5.4 SIMPLIFICATION OF CONSTANTS IN FRACTIONAL EQUATION
105
TABLES
FIGURES
107
108
CHAPTER 6:
APPLICATIONS OF PPFRC IN CIVIL
INFRASTRCUTURE
6.1 INTRODUCTION
113
6.2 APPLICATIONS IN BUILDINGS
114
6.3 APPLICATIONS IN BRIDGES
114
6.4 APPLICATIONS IN HIGHWAY PAVEMENTS
114
6.5 APPLICATIONS IN INDUSTRIAL FLOORING
115
6.6 APPLICATIONS IN DAMS AND HYDRAULIC STRUCTURES
115
6.7 APPLICATIONS IN BLAST RESISTANCE
115
6.8 APPLICATIONS IN SEWAGE AND WASTE WATER MANAGEMENT
116
6.9 OTHER APPLICATIONS
116
TABLES
117
FIGURES
118
iv
CHAPTER 7:
CONCLUSIONS AND RECOMMENDATIONS
7.1 CONCLUSIONS
124
7.2 RECOMMENDATIONS
125
APPENDICES
126
REFERENCES
139
v
LIST OF TABLES
Table 2.1
A compilation of mechanical properties of commonly used fibres in
concrete materials [ACI 544.5R, (2010)]
Table 2.2
Properties of different types of polypropylene fibres [S.K. Singh, (2010)]
Table 3.1
Polypropylene technical data sheet (MATRIXX)
Table 3.2
Mix proportion of concrete mixtures in Kg/m³
Table 3.3
Experimental matrix for workability tests
Table 3.4
Experimental matrix for shrinkage tests
Table 3.5
Experimental matrix for mechanical properties
Table 4.1
Test results of various fresh properties tests of PC and PPFRC with
different volume fraction and length of fibre
Table 4.2
Shrinkage test results of PC and PPFRC
Table 4.3
Weight measurements of PC and PPFRC
Table 4.4
Weight loss percentage of PC and PPFRC
Table 4.5
Displacement ductility calculated from experimental results for the flexure
tests of PC and PPFRC with different volume fraction and length of fibre
Table 5.1
Calibrated constants of the fractional equation for PC (Plain) concrete for
different strengths of concrete [Ahmad and Shah (1979, 1982, 1985)]
Table 5.2
Calibrated constants of the fractional equation for PPFRC with different Lf
and Vf .
Table 6.1
Typical dosages of PPFRC for various applications (MATRIXX
Company)
vi
LIST OF FIGURES
Figure 2.1
Main characteristics of fibres [Naaman et al, (2006)]
Figure 2.2
Composite model of FRC with two main components, namely fibre and
matrix [Naaman et al, (2006)]
Figure 2.3
Simplified general classifications of FRC composites based on their tensile
stress-strain response [Naaman et al, (2007)]
Figure 2.4
Typical stress-strain or elongation curve in tension up to complete
separation:
(a) Conventional strain-softening FRC composites; (b) Strain-hardening
FRC composites [Naaman et al, (2007)]
Figure 2.5
Schematic stress-strain behaviour of cementitious matrix in tension
[Gregor Fischer, (2004)]
Figure 3.1
Fibrillated polypropylene fibre
Figure 3.2
Polypropylene fibres of different length
Figure 3.3
The average compressive strength-time curve of 2”x2” mortar cubes
Figure 3.4
Pictorial view of rotary drum mixer
Figure 3.5
Pictorial view of freshly prepared FFRRC
Figure 3.6
Pictorial view of standard slump test apparatus [Eric et al (2003)]
Figure 3.7
Types of concrete slump[Eric et al (2003)]
Figure 3.8
Compacting factor test apparatus [Eric et al (2003)]
Figure 3.9
Pictorial view of flow table test apparatus [Technical Bulletin 1506]
Figure 3.10
Pictorial view of J-ring test apparatus [Eric et al (2003)]
Figure 3.11
Pictorial view of L-box test apparatus [Eric et al (2003)]
Figure 3.12
Pictorial view of V-funnel test apparatus [Eric et al (2003)]
Figure 3.13
Pictorial view of shrinkage moulds lined with plastic sheets
vii
Figure 3.14
Pictorial view of shrinkage specimen after casting
Figure 3.15
Pictorial view of length measurement instrument
Figure 3.16
Schematic view of standard shrinkage specimen
Figure 3.17
The universal testing machine
Figure 3.18
Schematic diagram of the compressive strength test setup
Figure 3.19
Schematic diagram of the tensile split test setup
Figure 3.20
Flexure test beam profile and section
Figure 3.21
Schematic diagram for flexure test
Figure 3.22
Pictorial view of the loading assembly for two-point flexure test
Figure 3.23
Pictorial view of the PPFRC beam while flexure test
Figure 4.1
Pictorial view of the slump cone after the removal of the standard slump
cone for PPFRC trial mix
Figure 4.2
Pictorial view of measurement of the weight of partially compacted fresh
concrete for evaluating Compacting factor
Figure 4.3
Pictorial view of measurement of the diameter of fresh concrete after flow
table test for PC.
Figure 4.4
Pictorial view of J-Ring test for PC
Figure 4.5
Pictorial view of J-Ring test for PPFRC 0.8-25
Figure 4.6
Pictoria view of L-Box test for PC
Figure 4.7
Pictorial view of L-Box test for PPFRC 0.8-38
Figure 4.8
Pictorial view of V-Funnel test for PC
Figure 4.9
Effect of fibre length (Lf ) on slump.
Figure 4.10
Effect of Fibre volume fraction (Vf ) on slump
Figure 4.11
Relationship between slump and compacting factor
viii
Figure 4.12
Relationship between slump and flow table diameter
Figure 4.13
Pictorial view of length measurement for PPFRC specimen
Figure 4.14
Average shrinkage-time curve for PC and PPFRC
Figure 4.15
Average weight loss-time curve for PC and PPFRC
Figure 4.16
Pictorial views of PPC and PPFRC specimens under compressive strength
test.
Figure 4.17
Pictorial views of PC and PPFRC specimens after compressive strength
test.
Figure 4.18
Effect of Vf on average compressive stress-strain curve for PC and PPFRC
with 25 mm long fibres at 7 days.
Figure 4.19
with 38 mm long fibres at 7 days
Figure 4.20
Figure 4.21
Figure 4.22
with 25 mm fibres at 28 days
Figure 4.23
with 38 mm fibres at 28 days
Figure 4.24
Effect of Lf on average compressive stress-strain curve for PC and PPFRC
with 0.4% volume fraction of PPF at 7 days
Figure 4.25
with 0.6% volume fraction of PPF at 7 days.
Figure 4.26
ix
Figure 4.27
Figure 4.28
Figure 4.29
Figure 4.30
Figure 4.31
Figure 4.32
Figure 4.33
Effect of Vf on average compressive strength-time curve for PC and
PPFRC with 25 mm long PP fibres.
Figure 4.34
Effect of Vf on average compressive strength-time curve for PC and
Figure 4.35
Effect of Lf on average compressive strength-time curve for PPFRC with
0.4% volume fraction of PP fibres.
Figure 4.36
Figure 4.37
Figure 4.38
Average splitting tensile stress-displacement curve for PC at 7 days
Figure 4.39
Pictorial view of PC specimen under split tensile strength test.
Figure 4.40
Effect of Vf on average splitting tensile stress-displacement curve for PC
and PPFRC with 25 mm long fibres at 7 days.
x
Figure 4.41
Figure 4.42
Figure 4.43
Figure 4.44
and PPFRC with 25 mm fibres at 28 days.
Figure 4.45
and PPFRC with 38 mm fibres at 28 days.
Figure 4.46
Effect of Lf on average splitting tensile stress-displacement curve for PC
and PPFRC with 0.4% volume fraction of PPF at 7 days.
Figure 4.47
and PPFRC with 0.6% volume fraction of PPF at 7 days
Figure 4.48
and PPFRC with 0.8% volume fraction of PPF at 7 days
Figure 4.49
Figure 4.50
Figure 4.51
Figure 4.52
Figure 4.53
xi
Figure 4.54
Figure 4.55
Pictorial view of crack propagation of PPFRC cylinder under splitting
tensile test.
Figure 4.56
Pictorial view of the split PPFRC cylinder
Figure 4.57
Effect of Vf on average splitting tensile strength-time curve for PC and
PPFRC with 25 mm long PP fibres
Figure 4.58
Figure 4.59
Effect of Lf on average splitting tensile strength-time curve for PPFRC
with 0.4% volume fraction of PP fibre
Figure 4.60
Figure 4.61
Figure 4.62
Pictorial view of the loading assembly for the two-point load flexure test.
Figure 4.63
Pictorial view of the PC beam after failure.
Figure 4.64
Pictorial view of the PPFRC beam during flexure testing, showing wide
crack and vertical displacement
Figure 4.65
Pictorial view of the PPFRC beam after collapse.
Figure 4.66
Pictorial view of the PC and PPFRC beam fractured surface after failure.
Figure 4.67
Effect of Vf on average flexure stress-displacement curve for PC and
PPFRC with 25 mm fibres at 28 days.
Figure 4.68
Effect of Vf on average flexure stress-displacement curve for PC and
xii
Figure 4.69
Effect of Lf on average flexure stress-displacement curve for PC and
PPFRC with 0.4% volume fraction of fibres at 28 days.
Figure 4.70
Figure 4.71
Figure 5.1
Typical analytical stress-strain curves of plain conrete of various strengths
(Ahmad and Shah, 1982)
Figure 5.2
Comparison of experimental and analytical compressive stress-strain curve
for PC at 28 days
Figure 5.3
for PPFRC 0.4-25 at 28 days
Figure 5.4
Figure 5.5
Figure 5.6
Figure 5.7
Figure 5.8
Figure 6.1
Application of PPFRC for plastering in multi-storeyed building,
Mehrunnisa Welfare Trust, Korangi, Karachi, Pakistan
Figure 6.2
Application of PPFRC in roof screeding, Creek Vista, DHA, Karachi,
Pakistan
Figure 6.3
Application of PPFRC in Jam Sadiq Bridge deck and expansion joint at
KPT Interchange, Karachi, Pakistan
xiii
Figure 6.4
Application of PPFRC in steel free pavements at Shaheen Air, Jinnah
Airport, Karachi, Pakistan
Figure 6.5
Application of PPFRC in industrial flooring of Razi & Sons, Port Qasim,
Karachi, Pakistan.
Figure 6.6
Application of PPFRC in the construction of water reservoir at Diamond
Terrace, Gulshan-e-Maymar, Karachi, Pakistan.
Figure 6.7
Application of PPFRC for blast resistance, Military College of
Engineering, Risalpur, Pakistan
Figure 6.8
Applications of PPFRC for sewage channel, Khayaban-e-Jami, DHA,
Karachi, Pakistan
Figure 6.9
Application of PPFRC for man holes in industrial zone, Landhi, North
Karachi, Pakistan
Figure 6.10
Application of PPFRC to reduce shrinkage cracking in column footing,
Karachi, Pakistan
Figure 6.11
Application of PPFRC to reduce abrasion resistance in concrete pavement,
Karachi, Pakistan.
xiv
LIST OF ACRONYMS
RC
Reinforced Concrete
FRC
Fibre reinforced concrete
PPFRC
Polypropylene Fibre Reinforced Concrete
PPF
Polypropylene fibres
ASTM
American Society for Testing Material
ACI
American Concrete Institute
SCC
Self-Consolidating Concrete
MSFRSCC
Micro-Synthetic Fibre Reinforced Self Consolidating Concrete
PC
Plain concrete
SNFRC
Synthetic fibrous concrete
WWF
Welded-wire fabric
PVA
Polyvinyl alcohol
HDPE
High-density polyethylene
FMF
Flexible metallic fibres
MR
Modulus of Rupture
UTM
Universal Testing Machine
FMF
Flexible metallic fibres
xv
LIST OF NOTATIONS
Lf =
Length of fibre
Vf =
Volume fraction of fibre
ΔL = Length change of specimen at any age, %
L=
Comparator reading of the specimen at known time interval
G=
Gage length (initial L)
T=
Splitting tensile strength
P=
Maximum applied load indicated by the testing machine
l=
Length, in. (m)
d=
Diameter, in. (m).
Ɛ'c = Peak strain (Ɛ'c)
A, D = Constants for fractional equation
xvi
ABSTRACT
The Polypropylene fibre reinforced concrete (PPFRC) contains randomly
distributed short discrete Polypropylene fibres which act as internal reinforcement so as to
enhance the properties of the cementitious composite (concrete). The principal reason for
incorporating short discrete fibres into a cement matrix is to reduce cracking in the elastic
range, increase the tensile strength and deformation capacity and increase the toughness
of the resultant composite. These properties of PPFRC primarily depend upon length and
volume of propylene fibres (PPF) used in the concrete mixture.
In Pakistan the polypropylene fibre reinforced concrete (PPFRC) has seen limited
applications in several structures. The applications are primarily to inhibit the cracking.
However due to the lack of awareness, design guidelines and construction specifications,
its uses are limited by the local construction industry. Therefore there is a need to
develop information on the properties of Polypropylene Fibre Reinforced Concrete
(PPFRC) in which indigenous polypropylene fibres are used in the concrete mixture.
A combined experimental and analytical study was undertaken. For the study,
fibrillated polypropylene fibres of two different lengths (lf) of 25 mm (1.00 in) and 38
mm (1.50 in) with 0.2%, 0.4% and 0.8% volume fractions (V f) of were used. The
research reported in this study includes an experimental investigation for measurement of
workability of PPFRC using two standard test methods to characterize consolidation and
four methods for flow property of PPFRC, an experimental investigation to characterize
selected mechanical properties of PPFRC and to study the effect of volume fraction of
(PPF) and length of PPF on the mechanical properties and; development of an analytical
model for predicting the stress-strain curves for PPFRC in compression. The comparison
of the analytical model for compressive stress-strain curve of PPFRC with the
experimental results is judged to be good.
xvii
ACKNOWLEDGEMENT
Praise to Almighty Allah, the most gracious and the most merciful. Without His blessings
and guidance our accomplishments would have never been possible.
Financial support and sponsorship of MATRIXX Company, F-37/A, Block 4, Clifton,
Karachi 75600, Pakistan, is gratefully acknowledged. Acknowledgement and gratitude is
extended to all those people who lent support at various stages of this work.
The author wishes to express deep gratitude and profound thanks to Prof. Dr. Shuaib H.
Ahmad (Foreign Professor, Department of Civil Engineering); for his motivation
encouragement & tremendous support and without whose encouragement and guidance
this work would not have been possible. Acknowledgment of support is also extended to
fellow graduate students and technicians in the laboratories of Civil Engineering
Department at NED University of Engineering and Technology.
Last but not least, the author’s wishes to thank and extend appreciation and gratitude to
the members of the family & friends who supported the efforts throughout this study.
xviii
DEDICATION
Dedicated to my loving parents Mr. and Mrs. Razi Muhammad Abidi and husband Mr.
Syed Fahim Hyder Naqvi
xix
CHAPTER 7
CONCLUSIONS AND RECOMMENDATIONS
7.1.
CONCLUSIONS
Based on research work conducted in this study, following conclusions can be made.
•
The addition of polypropylene fibres reduces the flow characteristics and
workability of the concrete mixture; however it also reduces bleeding and
segregation in the concrete mixture.
•
The mixing, placing, finishing and consolidation of the Polypropylene fibre
reinforced concrete (PPFRC) needs careful attention and control as the
performance of PPFRC is greatly affected by these.
•
The polypropylene fibres (PPF) reduce early age shrinkage and moisture loss
of the concrete mix even when low volume fractions of PPF are used.
•
Addition of the polypropylene fibres (PPF) has little or insignificant effect on
the compressive strength of plain concrete.
•
Addition of the polypropylene fibres (PPF) increases the deformation capacity
of concrete (in compression) and thus improves the material ductility of
concrete.
•
Addition of the polypropylene fibres (PPF) increases the energy absorption
capacity (area under the compression stress-strain curve) and thus improves
the material ductility of concrete.
•
In compression, the mode of failure of PPFRC is different from that of plain
concrete, as in the case of PPFRC, the fibres arrest the cracks, inhibit the fast
growth of cracks and smear the cracks over a larger area.
•
In tension, the post peak behaviour of the PPFRC is very significantly
improved from a perfect brittle behaviour for plain concrete to a relatively
ductile behaviour.
The addition of PPF fibres increase the post peak
deformation capacity by bridging the cracks that appear as the concrete
reaches its tensile strength.
•
In flexure loading (indirect tensile loading), the improvement in the behaviour
due to the addition of the PPF is the similar to that in tension. The plain
124
concrete beams exhibit a very brittle behaviour, whereas PPFC beams showed
ductile failure (increased deformation capacity) with formation of smeared and
wide cracks.
7.2.
RECOMMENDATIONS
•
The use of Polypropylene fibres (PPF) should be encouraged in various
applications in civil infrastructure.
•
The PPFRC should be used in combination with plain concrete to obtain cost
effectiveness.
•
The effect of PPF on the long term shrinkage and time dependent mechanical
properties should also be studied.
•
This study was conducted on plain concrete. Beneficial effects of PPF on
reinforced concrete for structural applications should also be studied.
•
Similar comprehensive studies should be conducted for hybrid FRC i.e.
combination of Steel and Polypropylene fibres.
125
APPENDIX-I
126
Microsoft Excel Programme for generating stress-strain curves in compression
Microsoft Excel Programme for generating stress-strain curves in splitting tension
127
Microsoft Excel Programme for generating stress-displacement curves in flexure
128
APPENDIX-II
129
List of projects where PPFRC was used in Concrete Pavement (MATRIXX,
2011)
Project Name
CONCRETE PAVEMENT
Project Address
PAF-Pakistan Air Force
Gatron Industries
Novatex Industries
Faisal House (Faisal Bank)
Siemens Factory
Pakistan Refinery Limited (PRL)
KANUPP, Karachi Nuclear Power Plant
Lucky Cement Factory
Al-Abid Silk Mills Ltd
Dewan Mushtaq Group
P.S.O
Kohat Cement Factory
Concrete Runaway, Faisal Base, Karachi.
Concrete Runaway, Pasni Base, Karachi.
Hub Chowki, Balochistan.
Korangi Industrial Area, Karachi.
Car Parking, Shahrah-e-Faisal, Karachi.
Generator Concrete Foundation, S.I.T.E., Karachi.
Workshop Parking Area, Korangi, Karachi.
Access Road, Paradise Point, Karachi.
Nooriabad, Karachi.
Industrial Concrete Pavement, Manghopir Road, Karachi.
Khoski Sugar Mill, Sindh
Keamari Oil Terminal-A, Karachi.
Kohat, Pakistan.
NHA-National Highway Authority
Concrete Rigid Pavement, Sibbi Toll Plaza, Balochitan.
Concrete Rigid Pavement, Dera Murad Jamali,
Balochistan.
Multan.
Pavement, S.I.T.E. Karachi.
Block-3, Clifton, Karachi.
NHA-National Highway Authority
City Developers
Futehally Chemical Pvt Ltd
CDGK, Ifza Park
Zaiqa Food Industries
Jinnah Hospital, Post Graduate Medical
Centre
S.C. Johnson’s Factory
Weatherford Oil Tool Middle East Ltd
Marine (Pvt) Ltd
Mustaqim Dyeing & Printing Industries
Yunus Textile Mills Limited
Snow White
Colgate Palmolive Pakistan Ltd, Factory
D.A. Golf Club
Jet Engine Testing House (PIA)
Shaheen Air International Ltd
Korangi Industrial Area.
F.B. Industrial Area, Karachi.
F.B. Industrial Area, Karachi.
S.I.T.E., Bada Board, Karachi.
Landhi Industrial Area, Karachi.
Korangi, Karachi
Karachi
Phase-8, DHA, Karachi.
Karachi
Jinnah International Airport, Karachi
Saya Industries
Loading & Unloading Area, Site, Karachi
National Industrial Parks
Dry Dock
International Power Global Developments
Ltd
PC Parking Karachi.
Karachi Nuclear Power Plant
U. G. Foods
Barma Soap
Port Qasim Authority, Karachi.
Manora, Kpt, Karachi
Karachi.
Hubco Power Station, Hub, Balochistan
Near PIDC Branch.
Near Paradise point, Karachi.
Bin Qasim, Karachi
Karachi
130
List of projects where PPFRC was used in Industrial Flooring (MATRIXX,
2011)
INDUSTRIAL FLOORING
Project Name
Project Address
Warehouse Concrete Flooring, Hub Chowki,
Gatron Industries
Balochistan.
Warehouse Concrete Flooring, Korangi
NovaTex Industries
Industrial Area, Khi.
Allied Engineering & Services Ltd
Industrial Area, Khi
Warehouse Concrete Flooring, Hub Chowki,
Baluchistan Wheels Ltd
Balochistan.
Warehouse Concrete Flooring, Keamari Oil
Shell Pakistan
Terminal, Khi.
P.S.O. Gas Filling Station
Warehouse Concrete Flooring, 14 Km,
PEL Pak Elektron Limited
Ferozpur Road, Lhr.
Valika Investment
Marine (Pvt) Ltd
Warehouse Concrete Flooring, Karachi
Warehouse Concrete Flooring, S.I.T.E.,
Maqbool GCP Ghee Mill
Karachi.
Colgate Palmolive
Warehouse Concrete Flooring, Kotri, Sindh.
Hub Power Company
Warehouse Concrete Flooring, Hub.
Gul Ahmed Textile Mills Ltd
Factory Flooring, Landhi, Karachi.
Factory Flooring, Super Highway (50 km),
Lucky Textile Mill Extension
Sindh.
Gulf Chemicals (Pvt) Ltd
Korangi Industrial, Karachi.
Tuwairqi Steel Mills Ltd
Bin Qasim Karachi
Khas Traders Factory
High Q Pharma
Insitu Terrazzo Flooring, Karachi.
Concrete Flooring at Car Parking, High-rise
MCB Tower
building, Karachi.
Aga Khan Planning & Building
Services
Garden Road, Karachi.
Kiran Gas (Pvt) Ltd
Hub Chowki, Balochistan.
Afroze Textile Industries (Pvt) Ltd
S.I.T.E., Super Highway, Karachi.
Shindler Futehally (Pvt) Ltd
Karachi.
Razi & Sons
Port Qasim Industrial Zone, Karachi.
Snow White
Pavement, Korangi, Karachi
Thal Engineering
Syntech Fibres Factory
LUMS
Sports Complex.
Lucky Textile Mill
Quaidabad, Karachi.
131
Jang Press
DA Sunset Club
Skyways Manufacturers (Pvt) Ltd
Karachi Club Annex
Expo Centre
Hamsons Towel Industries
Warid Telecom
KESC, Record Room
Pilot Social Welfare Complex, Habib
Group
Pakistan Atomic Energy
Sui Southern Gas Company Ltd.,
SSGC
Mustaqim Dyeing & Printing
Industries
Gertz Pharma (Pvt) Limited
Fay Motors
Pharma Evo
PPL Sui Purification Plant
Igloo Company
Derwaish, Warehouse
Sadr-Uddin & Sons
Meridian International (Pvt) Ltd
AG Sindh Complex
Huffaz Seamless Pipe Industries
Limited
Sultanabad Maikalachi Road, Karachi.
Khayaban-e-Jami, Phase II (Ext.), DHA,
Karachi
A/1-A-4, S.I.T.E., Karachi
Lalazar M.T.Road, Karachi
University Road, Karachi
Karachi.
Lahore.
Near Zenab Market, Karachi.
Malir (Near Rangers Head Quarter), Karachi.
New-2, Qayyumabad, Karachi.
Regional Building, Hyderabad.
D/14, A S.I.T.E., Karachi
Industrial Area, Karachi
Sultan Ahmed Shah Road Karachi
Port Qasim Authority, Karachi.
Sui, Balochistan
Cold Storage Karachi
Shershah, Karachi
Warehouse, Rashidabad, Karachi
F-10 Markaz, Islamabad
Karachi
Karachi
List of projects where PPFRC was used in Roof Screeding (MATRIXX, 2011)
ROOF SCREEDING
Project Name
Pakistan Security Printing Press
PARCO Pak-Arab Refinery Limited
Foundation Public School
DHL Head Office Building
Pakistan Navy, Special Children
School
Kiran Cancer Hospital
Horizon Pharmaceutical
TCS Overland Express Centre
BP Pakistan
Project Address
Korangi Base, Karachi.
Malir, Karachi.
Korangi Creek Road, Karachi.
Autoban Road, Hyderabad.
Shahrah-e-Faisal, Karachi.
Karsaz, Karachi.
A project of Pakistan Atomic Energy, Karachi.
Hill Park, Karachi.
Office / Warehouse, Jinnah International
Airport, Karachi.
Karachi.
132
Hafiz Tannery
NHA-National Housing Authority
PC-Pearl Continental Hotel
Creek Vistas, Creek City
CAA
Adamjee Enterprises
Agha Khan Estate Office
Hub School
Falcon Masjid
Memon Medical Institute, MMI
Hub Marble Factory
Uni Brow Industries
S. M. Public Husaini School
Pakistan Atomic Energy Commission
Aresha City
IBA, Existing Academic Block
Dairy Land
Indigo Textile (Pvt) Ltd
National Industrial Parks
Allied Engineering & Services Ltd
Afridi Motors
Zia Uddin Hospital Oncology
Department
Educational Institute charity.
Meezan Bank Ltd
FFBL
Sassui at N-5 Toll Plaza Control Building,
Karachi.
Gwadar, Balochistan.
Phase 8, DHA, Karachi.
Radar Station, Quaid-e-Azam Airport, Karachi.
Adamjee Nager, Karachi
FB Area, Karachi.
At Dam Road.
SDH Colony, Malir Cantt, Karachi.
Safoora Goth, K.D.A., Scheme 33, Karachi.
Marble City, Hub.
S.I.T.E. Karachi.
Nazimabad, Karachi.
Workshop Building, Korangi, Karachi.
Gulzar-e-Hijri, Scheme 33, Karachi.
Pakistan Atomic Energy Commission.
Main Campus IBA, Karachi
I.I. Chundrigar Road, Karachi.
Joreji Bin Qasim, Karachi
Shahrah-e-Faisal, Karachi
Korangi Industrial Area, Karachi
Peshawar
Nazimabad, Karachi.
North Nazimabad, Karachi.
C-25, SITE, Karachi
PQA, Karachi
List of projects where PPFRC was used in Concrete Plastering (MATRIXX,
2011)
CEMENT CONCRETE PLASTER
Project Name
Project Address
Indus Hospital
Korangi, Karachi.
KPT-Karachi Port Trust, OP1
Karachi.
Aga Khan Education Service
School in Gilgit & Hunza.
Madarsa Fatima-tuz-Zahra
Khairpur, Sindh.
Mehrunnisa Welfare Trust
Korangi, Karachi.
Techno Pak Telecom
Tipu Sultan Road, Karachi.
Bahria College NORE1
Karachi.
Renovation Plaster, Jinnah Intl. Airport,
Mercure Grand Hotel (Accor Hotel)
Karachi.
Dow Medical University & Hospital
Safoora Goth, Karachi.
133
Pakistan Navy, Special Children
School
Crescent Investment Bank
Aga Khan University & Hospital
Asian Pharmaceutical (CCC)
Siemens Grid Station
Macter International (Pvt) Limited
Askari 4 Housing
Tollink Pakistan (Pvt) Ltd
Squash Court Faisal Base
Sindh Club
The Aga Khan University
Indus Pharma (Pvt) Ltd
Telenor Building
Bosicor Pakistan Limited
Uch Power Plant
SOS Village
Government Boys & Girls School
Usmani Colony Govt Girls & Boys
School
Sarjani Town Girls & Boys School
Aresha City
Star City
GSK Glaxo Smith Kline Pharma
Reckitt Benckiser Pakistan Ltd
Zia Uddin Hospital Oncology
Department
Tayyaba Mosque
Stock Exchange Building
ERRA-60 School Projects
Civil Hospital
Cotton Exchange Building
King Stone
U. S. Consulate
Degree College,
Purification Plant
Inaara Garden
Immigration Tower
Khairpur University
Girls College
Boys College
Byco
Trade Corporation of Pakistan
Karsaz, Karachi.
Phase-2 Extension.
Sports Complex, Karachi.
Renovation Works, Tipu Sultan Road, Karachi.
Hub, Balochistan.
Site, Karachi.
Rashid Minhas Road, Karachi.
Plaster & Screed Works
Karachi.
Abdullah Haroon Road, Karachi.
Emergency Department, Karachi.
Sector-27, KIA, Karachi.
Near Centrum, Gulshan-e-Iqbal, Karachi
Karachi
Dera Murad Jamali, Balochistan.
Malir Cantt, Karachi.
Yousuf Goth, Karachi.
Jail Road, Karachi.
Sarjani, Karachi
Gulzar-e-Hijri, Scheme 33, Karachi.
Garden Road, Karachi.
West Wharf, Karachi.
Karachi.
Nazimabad, Karachi.
Islamabad
Islamabad
Northern Area of Pakistan.
Karachi.
I. I. Chundrigar Road, Karachi.
Phase 6 DHA, Karachi, Plaster
Mia Kolachi, Karachi
Dheer Kot , Bagh, AJK
Dharki
Near Saadi Town, Karachi
Islamabad
Khairpur, Miras, Sindh
Bagh, AJK
Bagh, AJK
Near Hubco Power Plant
Khairpur.
134
ISM Hospital
GSK Glaxo Smith Kline Pharma
Allied Bank Office Building
Pfizer Laboratories Ltd
Near Sobhraj Hospital Garden, Karachi.
Processing Zone Landhi, Karachi
Karachi.
List of projects where PPFRC was used in Underground Structures (MATRIXX,
2011)
BASEMENT & UNDERGROUND STRUCTURE
Project Name
Project Address
Basement Structure Concrete work, Dera Ismail
Residential Villas for UAE Govt.
Khan, Punjab
Karachi Gym Khana
Basement Concrete works, Karachi.
Basement Concrete works, Gulshan-e-Maymar,
Diamond Terrace
Karachi.
Mercure Grand Hotel (Accor Hotel)
Slab on Grade, Jinnah Intl. Airport, Karachi.
Colgate Palmolive
Concrete Foundation Works, Kotri, Sindh.
Government S.M. Public School, Nazimabad.
Education & Health Works CDGK
Karachi.
Grey Tower
Phase 5, DHA, Karachi
Aresha City
Near Hamdard University, Karachi.
OGDCL
Hyderabad
Pakistan Refinery Limited (PRL)
Korangi Creek Road, Karachi.
List of projects where PPFRC was used in Bridges (MATRIXX, 2011)
BRIDGES
Project Name
KPT Interchange Bridge
KPT Fly Over
Hasan Square Interchange Bridge
Johar Mohr Bridge
Quaidabad Bridge
PICT Fly Over
Gizri Fly Over
Shershah Bridge
Project Address
Korangi Road, Karachi.
Near Kemari, Karachi.
Civic Center, Karachi.
Gulshan-e-Jauhar, Karachi
Quaidabad Chawrangi, Karachi.
Karachi.
Kh-e-Hafiz, Gizri Commercial Area, Gizri,
Karachi.
SITE, Karachi
List of projects where PPFRC was used in Hydraulic Structures (MATRIXX,
2011)
WATER TANKS & RESERVOIRS
Inter Continental Hotel
Swimming Pool Concrete Works, Islamabad.
Zaver Pearl-Continental Hotel
Water Reservoir Concrete Works, Gwadar.
135
DHA
Caltex Oil Pvt Ltd
Hamson (Pvt) Ltd
Maymar Housing Services (Pvt) Ltd
ACACIA Country & Golf Club
Waste Water Treatment Plant
Sindh Club
Diamond Terrace
Rashid Memorial Welfare
Organization
Star City
National Refinery Limited
Nur Farm
Daily Khabrian
SUPARCO
Rehman Dying
Centre Point
Pakistan Atomic Energy Pakistan
Benazir Bhutto International Airport
Sofitel Hotel Tower
IBA Main Campus
Textile City
Water Reservoir Concrete Works, Phase-VI,
Karachi
Underground, Korangi Industrial Area, Karachi.
Water Retaining Structure, Landhi Industrial
Zone, Karachi
Water Retaining Structure, P.E.C.H.S., Karachi
Water Retaining Structure, Karachi.
Am Textile, Jarawala Road, Faisalabad.
Abdullah Haroon Road, Karachi.
Gulshan-e-Maymar, Karachi.
30 Km of Hyderabad.
Opp Bambino Cinema Karachi
Karachi.
Canal Lining, Hyderabad
Multan.
Head Quarter, Safoora Goth, Karachi.
Normal Water Tank Super High Way Site
Trakker Tower, Shaheed-e-Millat, Karachi
Lahore.
Islamabad
Main Clifton Road, Karachi
Karachi
PQA, Karachi
List of projects where PPFRC was used in Sewerage Drains (MATRIXX, 2011)
SEWERAGE DRAINS
Project Name
Project Address
Pakistan Defence Officers Housing
Sewage Channel, Khy-e-Jami, DHA, Karachi
Authority (DHA)
KWSB
Manhole, Landhi Industrial Zone, Karachi.
KWSB
Manhole, FB Industrial Zone, Karachi.
KWSB
Manhole, Korangi Industrial Zone, Karachi.
Manhole, North Karachi Industrial Zone,
KWSB
Karachi.
KWSB
Manhole, Sherpao Industrial Zone, Karachi.
Sewage Channel, Landhi Industrial Zone,
KWSB
Karachi.
List of projects where PPFRC was used in Marine Structures (MATRIXX, 2011)
MARINE STRUCTURES
136
Project Name
Korangi Fisheries Harbour Authority
KPT Karachi Port Trust
Zara Textile
Hyeworth
Reckitt Benckiser Pakistan Ltd
KPT, OP3, Oil Pair 3
Project Address
Rehabilitation Concrete Work of Jetty, Chasma
Goth, Karachi
Floating Jetty East Wharf, Karachi
Beach Hut, S-96, Sandspit, Karachi.
Beach Hut, S-30, Sandspit, Karachi.
Beach Hut, N-49, Sandspit, Karachi.
Kemari
List of projects where PPFRC was used in Precast Structures (MATRIXX, 2011)
PRECAST STRUCTURES
Project Name
Project Address
Marine Cable Cover, Hawks Bay, Arabian Sea
PTCL Main Fiber Optic Line
(Dubai) to Khi.
AL-Mohammadi Tile
D.I.H. Korangi, Karachi.
Randhawa Pre-Cast Factory
Landhi, Karachi.
Concrete Measures
Exporter of Paver, Stepping Stone, Karachi.
Cellpor Building Solution
DHA, Phase IV, Karachi.
CONEX
Phase-II Ext, DHA, Karachi
Concrete Wizards
Factory I-9, Islamabad.
Concrete Core
Korangi Industrial Area, Korangi, Karachi.
Kumhar TerraCotta & Concrete
Gulshan-e-Mehran Malir, Karachi
Envision
Consulate General of the Islamic
Karachi
Republic of Iran
List of projects where PPFRC was used in Repair Applications (MATRIXX,
2011)
CRACK REPAIR APPLICATORS
Project Name
Project Address
Burhani Impex
Bhora Pir, Karachi.
Con-Link International
North Nazimabad, Karachi.
Techno Plus
Gulshan-e-Iqbal, Karachi.
Concrete Technology
Karachi.
Protection Technology
Shahrah-e-Faisal, Karachi.
Pak-Binder
Karachi.
Dubai Palace
Karachi
Parco
Pipri
137
List of projects where PPFRC was used in Shotcrete Rehabilitation (MATRIXX,
2011)
SHOTCRETE REHABILITATION
Project Name
Project Address
Korangi Fisheries Harbour Authority Sea Marine Structure, Karachi.
ERRA Rehabilitation Work
Roof Slab, Islamabad
138
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143
CHAPTER 1
INTRODUCTION
1.1.
BACKGROUND
Concrete is the most commonly used construction material worldwide. In Pakistan,
reinforced concrete (RC) is extensively used in the construction of variety of civil
infrastructure applications including small and large buildings, houses, bridges, storage
tanks, dams and numerous other types of structures in Pakistan.
Concrete is a brittle, composite material that is strong in compression and weak in
tension. The tensile strength of plain concrete is about 10% of its compressive strength.
Cracking occurs when the concrete tensile stress produced from the externally applied
loads, temperature changes, or shrinkage in a member reaches the tensile strength of the
material. Formation of tensile cracks in reinforced concrete flexural members containing
conventional, non-prestress reinforcement is usually unavoidable since concrete has a
low tensile straining capacity. While cracks barely wide enough to be visible may be
objectionable only because of appearance, cracks of greater width can be dangerous
because of the possibility of corrosive agents attacking the steel reinforcing bars.
Excessively wide cracks can also result in leakage in such structures as dams, tanks, and
pools. In many of the cases this cracking is so significant that it may lead to failure of the
structure. The deterioration of such structures is of great concern since the repairing and
rehabilitation of these structures are time consuming and costly. Hence there is an
intense need to take measures that can control the cracking of concrete and thus cause
overall safety of a structure and increase its useful life. Use of short discrete fibres in
cementitious composites (concrete) is one approach to mitigate the cracking and
increasing the tensile straining capacity.
1
The fibre reinforced concrete (FRC) contains randomly distributed short discrete fibres
which act as internal reinforcement so as to enhance the properties of the cementitious
composite (concrete). The principal reason for incorporating short discrete fibres into a
cement matrix is to increase the toughness and tensile strength, and to improve the
cracking deformation characteristics of the resultant composite. These properties of FRC
primarily depend upon the type of the fibres used in the concrete.
Several different types of short discrete fibres have been used to reinforce concrete. The
choice of fibres varies from synthetic organic materials such as polypropylene or carbon,
synthetic inorganic such as steel or glass, natural organic such as cellulose or sisal to
natural inorganic asbestos. Short discrete steel, glass, polyester and polypropylene fibres
are most commonly being used as reinforcement to the FRC. The selection of the type of
fibres is guided by the properties of the fibres such as diameter, specific gravity, young’s
modulus, tensile strength etc. and the extent these fibres affect the properties of the
cement matrix.
Polypropylene fibres are chemically inert, and so will not rust, corrode or rot, and will not
absorb water. Little or no flame spread on the surface of polypropylene fibre reinforced
panels was reported in laboratory tests. The introduction of polypropylene fibres in
concrete affects its properties both in fresh and hardened state. In fresh state it may
reduce the workability and the also slows down the rate of bleeding. It may also increase
the setting times for the concrete. However in hardened state, polypropylene fibres act as
crack arrestors. Like any secondary reinforcement, the short discrete fibres tend to
mitigate the crack propagation by bridging the cracks and providing increased resistance
to crack propagation. Recently, fibrillated polypropylene fibres (lattice type structure
when filament is opened up) have been introduced. The structure of the fibrillated
polypropylene fibres is such that it provides three dimensional reinforcement to the
cementitious matrix thus; enhancing tensile strength, tensile strain capacity and the
improved resistance to impact and fatigue.
2
In Pakistan the polypropylene fibre reinforced concrete (PPFRC) has seen limited
applications in several structures including parking areas, drive ways, industrial floorings,
water and other chemical storage tanks, walkways, pavements, roof screeds, mosaic
flooring, structural concrete and also in pre-cast slabs. The applications are primarily to
inhibit the cracking. However due to the lack of awareness, design guidelines and
construction specifications, its uses are limited by the local construction industry.
Therefore there is a need to develop information on the properties of Polypropylene Fibre
Reinforced Concrete (PPFRC) in which indigenous polypropylene fibres are used.
1.2.
OBJECTIVE AND SCOPE
The objectives of this research are:
1)
Conduct experimental investigation for measurement of workability of
Polypropylene Fibre Reinforced Concrete (PPFRC).
2)
Conduct experimental and analytical investigation to characterize
principal mechanical properties of PPFRC and to study the effect of volume
fraction and length of polypropylene fibres (PPF) on the mechanical properties.
The scope of this research is limited to the fibrillated polypropylene fibres of length 25
mm (1.00 in.) and 38 mm (1.50 in.). For the measurement of workability of the PPFRC,
two standard methods are used for characterizing workability in terms of consolidation,
however; four standard test methods are used to characterize the flow property of PPFRC.
For the mechanical properties, the following tests are conducted to study the effect of
amount of fibres and the length of fibres on the compressive, tensile and flexure strength
and the associated straining capacity.
1) Compressive Strength of concrete cylinders (ASTM C39)
2) Split Tensile Strength of concrete cylinders (ASTM C496)
3) Flexure Strength of concrete beams under two point loading (ASTM C78)
3
The shrinkage characteristics of plain and PPFRC were studied using ASTM C157
standard test method. This method is used for measuring the length change of hardened
mortar or concrete specimens.
1.3.
RESEARCH SIGNIFICANCE
The use of PPFRC in the local construction industry is limited. The purpose of this work
is to develop evidence of the engineering properties of PPFRC in which indigenous
polypropylene fibres are used.
This includes the properties of PPFRC such as
workability in fresh state, free shrinkage and other mechanical properties in hardened
state.
The results of this work will be useful for the local construction industry and could be
used for developing specification guidelines for the use of PPPFC in the local
construction.
1.4.
METHODOLOGY
The research methodology was to conduct a literature review of the studies on FRC and
PPFRC that have been conducted in the past two decades. On the basis of the literature
review, knowledge gaps were identified. It was realized that mechanical properties of
Polypropylene fibre reinforced concrete have been studied by many researchers in
different areas of world; however in Pakistan there still a need to provide experimental
and knowledge ground for the use of PPFRC in the local construction industry. An
experimental program was developed to study the properties of PPFRC in fresh and
hardened state. The experimental program included number of variables such as the
length of the PPF (Lf), amount of PPF (Vf), test age etc. Concrete mixture proportions
for plain and PPRC concrete were developed to maintain a target slump. Using these
PPFRC concrete mixes, test specimens were cast, cured and tested as per the
experimental matrix. The results of the plain and PPFRC concrete test specimens were
compared to quantify the beneficial effects of PPF on concrete. The results are discussed
4
and presented along with an analytical equation for characterizing the stress-strain curve
of PPFRC in compression.
1.5.
ORGANIZATION OF THE THESIS
This report is organized into seven chapters. Details of each chapter are described as
follows.
1.
Chapter 1 gives an introduction to the report.
2.
Chapter 2 presents a literature review of the researches related to the
workability and mechanical properties of the PPFRC conducted in the past
two decades.
3.
Chapter 3 presents the experimental investigation that gives a detailed
description about the materials, casting and curing of the test specimens,
and the test set ups for the laboratory work.
4.
Chapter 4 presents the test results and discussion of the results.
5.
Chapter 5 gives analytical solution of the stress-strain curves of PPFRC in
compression using fractional equation.
6.
Chapter 6 indicates some common applications of PPFRC in civil
infrastructure in Pakistan.
7.
Chapter 7 summarizes the research work, presents conclusions and offers
recommendations for future research.
5
CHAPTER 2
LITERATURE REVIEW
2.1.
INTRODUCTION
This chapter presents the review of studies conducted on the history, performance and
behaviour of FRC and the properties of different fibres that affect the performance of the
composite. The studies conducted in the past two decades are mainly focused.
2.1.1. Historical Evolution of FRCC
The use of randomly distributed fibres in concrete is not new. Since ancient times, fibres
like straws, horse hair and other vegetable fibres have been used to reinforce brittle
materials [ACI 544.1R (1996)]. However after 1960’s, a great evolution took place in
this regard and a number of different fibres and other materials were introduced to
enhance the most significant mechanical properties of concrete.
The use of those
materials was supported by an extensive number of research results showing the ability of
fibres to improve the mechanical properties and durability of concrete.
Modern
developments and world-wide interest on the subject took off during the early 1960’s
following studies by Romualdi on the use of steel fibres in concrete [Romualdi et al
(1964), Romualdi et al (1969)]. Use of glass fibres in concrete was first attempted in the
late 1950s by Biryukovich [Biryukovich et al (1965)].
After this initial work, a
substantial amount of research, development, experimentation, and industrial application
of fibre reinforced concrete has occurred.
2.1.2. Classification of fibres
A wide variety of fibres have been used in concrete. For each application it needs to be
determined which type of fibre is optimal in satisfying the concrete application. The
different types of fibres used as concrete reinforcement are synthetic fibres and steel
6
fibres. The different types of synthetic fibres used are Polypropylene, Nylon, Polythene,
Polyester and Glass Fibres.
For architectural and decorative concrete products and for prevention of early age
cracking, synthetic fibres may be used. Steel fibres are used for applications where
properties of concrete in the hardened stage have to be modified, namely, post crack
flexural strength, abrasion resistance, impact resistance and shatter resistance of concrete
[Clinton Pereira (2009)].
The majority of materials used in fibre production and the typical range of mechanical
properties for each fibre type are summarized in Table 2.1 [ACI 544.5R (2010)]. A more
comprehensive classification “system” of these fibres (Figure 2.1) is given by
Naaman[(2006)]. In this system, the characteristics of the fibres are categorised into four,
namely the geometrical properties, mechanical properties, physical/chemical properties
and material type. For practical utilisation of fibres in FRC applications, properties
which are given significant considerations in selection of fibres are material type, tensile
strength, elastic modulus and the aspect ratio (the ratio of fibre length to the diameter or
equivalent diameter).
2.1.3. Fibrillated Polypropylene Fibre
Previously, problems were encountered in mixing, workability and durability of fibre
reinforced concrete but these have almost been overcome by the emergence of new types
of synthetic fibres. Polypropylene Fibre is one amongst them. The primary advantages of
polypropylene fibre over others are its easily tailoring properties and its resistance against
corrosive attack of the environment.
Polypropylene fibres are actually man-made synthetic fibres resulted from research and
development in the petrochemical and textile industries.
These fibres derived from
organic polymers which are available in a variety of formulations [ACI 544.1R (1996)].
7
Table 2.2 gives physical properties of different types of Polypropylene Fibres namely,
Monofilament, Microfilament and Fibrillated fibres [S. K. Singh (2010)].
2.1.4. Fibre Reinforced Cementitious Composites
ACI 544.3R-08 defines Fibre Reinforced Concrete, (FRC) as a composite material made
of hydraulic cements, water, fine and coarse aggregate, and a dispersion of discontinuous
fibres [ACI 544.3R (2008)].
Naaman proposed a composite model to define FRC as a composite with two main
components, namely the fibre and the matrix, as indicated in Figure 2.2. In this model,
both the fibre and the matrix are assumed to work together through bond, providing
synergism for an effective composite [Naaman (2006)].
Naaman classified fibre reinforced cementitious composites into two broad categories
according to their tensile response, namely, either Strain-Softening or Strain- Hardening.
(Figure. 2.3) Strain-softening FRC composites (Figure. 2.4a) exhibit strain softening and
crack localization immediately following first cracking whereas Strain-hardening FRC
composites are characterized by a stress-strain response in tension that exhibits strain
hardening behaviour after first cracking, accompanied by multiple cracking (Figure.
2.4b).
First cracking here implies a through the section crack or percolating crack
[Naaman (2007)].
Another classification of fibre reinforced cementitious materials on the basis of structural
applications is given by Stang et al [(2004)]. According to that, the general mechanical
response of these materials under uniaxial state of stress can be either of the three:
i.
Tension softening response is so significant that it can be allowed to
be taken into account in structural design,
ii.
The strain hardening
portion is significant enough that it can be
taking into account in structural contexts, or
iii.
Both the hardening and the softening regimes are significant enough
to be taken into account in structural design.
8
2.2.
FRESH (PLASTIC) PPFRC
2.2.1. Workability
American Concrete Institute (ACI) Standard 116R-90 defines workability as “that
property of freshly mixed concrete which determines the ease and homogeneity with
which it can be mixed, placed, consolidated, and finished.”
[ACI 116R (1990)]
Workability is the measure of the ability of concrete to be mixed, handled, transported,
placed, and consolidated. Workability plays key role in the performance of hardened
product. The strength and serviceability properties of FRC are greatly affected by the
mixing, dispersion, consolidation and hydration of fresh FRC. Hence it is mandatory to
ensure good flowability, placeability, segregation resistance and uniform dispersion of
fibres in the fibre reinforced concrete.
Fresh concrete properties and workability
(flowability, passing ability and segregation resistance) determined by different methods
were reported for polypropylene fibre reinforced concrete having different fibre content
that is percentage by volume.
Most of the studies conducted to evaluate the workability of the fibre reinforced concrete
deal with the flow property of Self-Consolidating Concrete (SCC), which is one kind of
high performance concrete. The main character of self-compacting concrete is that there
is no need of vibrating during construction process, reducing manpower demand in the
construction stages of concrete structures. Among those, most of the researchers have
focused on the effect of steel fibres on the rheology of SCC mixtures and the
development of steel fibre-reinforced self-consolidating concrete mixture design
procedures [Toutanji et al (1998), Mustafa et al (2007), Li et al (2011), Abdulkadir et al
(2007), Stähli et al ( 2008), B. Krishna Rao et al (2010), Mustafa Sahmaran et al (2005)].
Fewer studies [D. Forgeron et al (2010), S.K. Singh (2010)] have been conducted on
synthetic fibre reinforcement and its effect on the flow characteristics of SCC. It is
therefore important to study the flow characteristics of self-consolidating concrete
mixtures that incorporate this type of synthetic fibre reinforcement in order to identify
and characterise the main factors affecting its flow.
9
2.2.1.1. Uniform Dispersion of Fibres
Mixing of FRC can be accomplished by several methods, with the choice of method
depending on the job requirements and the facilities available. It is important to have a
uniform dispersion of the fibres and to prevent the segregation or balling of the fibres
during mixing. Balling of the fibres during mixing is related to a number of factors. The
most important factors appear to be the Aspect Ratio of the fibres, the volume percentage
of fibres, the maximum size and gradation of the aggregates, and the method of adding
the fibres to the mixture. As the first three of these factors increase, the tendency for
balling increases [A. L. Ardeshana et al (2012)]. Therefore, before mixing the concrete,
the fibre length, amount and design mix variables are adjusted to prevent the fibres from
balling. The aspect ratio for the fibres are usually restricted between 100 and 200 since
fibres which are too long tend to "ball" in the mix and create workability problems.
There should be sufficient compaction so that the fresh concrete flows satisfactorily and
the PP fibres are uniformly dispersed in the mixture [S.K. Singh (2010)].
2.2.1.2. Setting time
Addition of fibres in concrete reduces the amount of bleed water form concrete and so the
rate of bleeding decreases. The use of polypropylene fibres may increase the time to
initial and final set of the concrete as this led to a slower rate of drying in the concrete
[S.K. Singh (2010)].
Alhozaimy (1995) investigated the effect of polypropylene fibres on the initial and final
setting time of concrete and found that the initial and final setting times were decreased
by 9 and 27 percent, respectively, with the addition of polypropylene fibres.
This
reduction is expected to reduce the period of exposure prior to setting of fresh concrete to
the dry environment, which is responsible for plastic shrinkage cracking. The amount of
bleed water for plain and fibrous concretes was also reduced. Due to the addition of
polypropylene fibres, there was an 18 percent decrease in the amount of bleed water of
concrete; the fibres possibly reduce the settlement of heavier mix constituents (e.g.,
10
aggregates), thereby reducing the upward movement of water (bleeding) in concrete
[Alhozaimy et al (1995)].
2.2.1.3. Filling Ability, Flowability and/or Passing Ability
The main parameter, which is often used to determine the workability of fresh concrete,
is the slump test. The slump value depends mainly on the water absorption and porosity
of the aggregates, water content in the mixture, amount of the aggregate and fine material
in the mixture, shape of the aggregates and surface characteristics of the constituents in
the mixture. The slump values decrease significantly with the addition of polypropylene
fibres.
The concrete mixture becomes rather clingy resulting in increasing of the
adhesion and cohesiveness of fresh concrete. During mixing the movement of aggregates
shears the fibrillated fibres apart, so that they open into a network of linked fibre
filaments and individual fibres. These fibres anchor mechanically to the cement paste
because of their large specific surface area. The concrete mixture with polypropylene
fibres results in the fewer rate of bleeding and segregation as compared to plain concrete.
This is because the fibres hold the concrete together and thus slow down the settlement of
aggregates [S.K. Singh (2010)].
Forgeron and Omer studied the effect of length of fibre on the flow characteristics of
Micro-Synthetic Fibre Reinforced Self Consolidating Concrete (MSFRSCC) by using 20
non-air entrainment self-consolidating concrete (SCC) mixtures with varying w/c ratios,
self-fibrillating Polypropylene macro-synthetic fibre lengths of 38 mm (1.5 in) and 50
mm (2 in) and fibre volume fractions from 0.2% to 0.5%. The flow characteristics of
each mixture were evaluated using four typical SCC workability test methods: slump
flow, filling capacity, L-box, and V-funnel flow time tests. The results showed that the
fibre length plays a very important role in the flow characteristics. Comparing the flow
characteristics, both the fibre lengths showed acceptable slump flows but the Slump flow
of concrete with 50 mm (2 in) long fibres was found the least. Concrete having 0.5% of
50 mm long fibres was found to be worst in filling and flow property as it showed a
11
minimum of 65% filling capacity and a blockage in V-Funnel Test [D. Forgeron et al
(2010)].
In 2011, Zhiguo You et al compared the workability of fibre reinforced self-consolidating
concretes with two steel fibres of different aspect ratio and one synthetic fibre using
standard Slump Flow and J-Ring Test. The test results showed that 40 kg/m³ (2.5 lb/ft³)
steel fibres and 4 kg/m³ (0.25 lb/ft³) plastic fibres can be the upper bound of the fibre
content regarding the workability of SCC [Zhiguo You et al (2011)].
2.2.1.4. Volume Stability
The serviceability of portland cement concrete (PCC) and of reinforced concrete
structures is closely associated with their ability to resist and control cracking. There are
many causes of cracking on brittle cement concrete mixes; volume change is one of them.
Volume change causes cracking in concrete both in plastic (early age) concrete and
Hardened Concrete. The use of fibre reinforcement in concrete reduces cracking and
shrinkage and thus ensures volume stability of the cementitious composite to a great
extent [Isabel Padron et al (1990)].
2.2.2. Early Age and Plastic Shrinkage
Plastic shrinkage cracking of concrete occurs when it is exposed to drying environment
while it is still in plastic form. Normally it occurs within the first few hours after the
concrete is placed and before it attains any significant strength. The adverse effects of
drying shrinkage at a very initial phase include an unsightly and non-uniform appearance
on the concrete surface. Later, the plastic shrinkage cracks become critical weak points
for aggressive substances to penetrate into the internal portion of concrete leading to the
acceleration of other detrimental forms of concrete deterioration. Consequently, the
performance, serviceability, durability, and aesthetic qualities of concrete structures are
reduced. Controlling plastic shrinkage cracking in concrete is essential for developing
more durable and longer-lasting structures at a minimum life-cycle cost [Naaman et al
(2005), Shah et al (2004)].
12
One of primary causes of plastic shrinkage cracking is the loss of water from evaporation
that leads to a built-up tensile shrinkage stress when concrete is subjected to sufficient
restraint. When the rate of water loss due to evaporation exceeds the rate at which the
bleed water is supplied to the surface, negative capillary pressures form that result in
volume changes in the concrete. Tensile stresses in the paste form due to the negative
capillary pressure and the development of strength in the concrete. Cracking occurs if the
tensile stresses are greater than the tensile strength of the concrete [Naaman et al (2005),
Shah et al (2004)].
The most effective method to prevent the plastic shrinkage of concrete that has become
more and more popular in the last two decades is to add fibres to the matrix of the
concrete. Such fibres are supposed to be randomly distributed and can be of different
materials and geometries.
Dependent on the volume, the added fibres improve the
shrinkage cracking behaviour of the concrete by either simply bridging cracks after their
occurrence (lower volumes) or increasing the actual tensile strength of the matrix and
thereby delaying or preventing the cracking (higher volumes) [Naaman et al (2005), Shah
et al (2004)].
2.2.2.1. Experimental and Analytical Methods to Study Plastic
Shrinkage
Numerous strategies have been advocated to reduce the potential for plastic shrinkage
cracking in concrete through mixture proportioning, curing methods, or the use of fibre
reinforcement. The effectiveness of each approach must be adequately quantified to
determine whether the additional initial cost of each strategy is justified. The majority of
current research to characterize plastic shrinkage cracking in concrete relies on manual
crack observation and measurement that is typically only performed at selected locations.
These manual measurements of crack width may provide only limited information and
may be subject to operator bias. This section describes some systematic methodologies
to accurately quantify the salient features of the plastic shrinkage cracking.
These
methodologies are developed by utilizing different techniques such as Image Analysis,
13
Modified Weibull Function, and by using Demec gauges [Santhanam et al (2006),
Christopher et al (2007), C. Qi et al (2003)].
Santhanam (2006) used a simple and reproducible technique to monitor plastic shrinkage
cracking in rectangular concrete slabs. This methodology was found to be successful
even for the characterization of very fine cracks in hybrid fibre concrete systems. This
was based upon image analysis of photographs and manual crack measurements. In this
study, the crack measurements were made after 24 hours in order to ensure that cracks
got fully developed and stabilized. The cracked area was then photographed using a 4x
optical zoom digital camera, and the image was processed using image analysis software.
In order to calibrate the original size of the image that was captured, a measuring scale
was placed on the concrete specimen and the entire area was photographed. The distance
between two points on the scale was calibrated in terms of pixels and the total pixels were
converted to the desired unit. The very thin hairline cracks were studied manually using
a crack width microscope, which can measure accurately the crack widths in the range of
0.025 to 2.5 mm. (0.00098 to 0.098 in.).
Shrinkage cracks were observed in less than about 4.5 hours after casting for the control
concrete and 5.5 and 7 hours for the steel fibre and hybrid fibre concretes respectively.
For the control concrete, the maximum crack width obtained was 0.5 mm (0.0196 in.);
this was reduced to 0.371 mm. (0.0146 in) i.e. by 25% in the case of steel fibre concrete
(SFRC), and to 0.225 mm. ( 0.0088 in.) i.e. by 55% in case of hybrid fibre concrete. This
corresponds to a reduced crack area of 57.6 % compared to control concrete and 43%
compared to steel fibre concrete [Santhanam et al (2006)].
Christopher et al (2007) investigated a new test procedure to study the shrinkage cracking
behavior for plain shotcrete and four different types of FRS (polypropylene, steel,
polyvinyl alcohol, and hybrid). To introduce shrinkage restraint, specimens cut from a
shotcrete panel are bonded to a steel fixture. This method utilizes the measurement of
shrinkage strain of the restrained specimen at different times, the occurrence of cracking
can be easily observed from a sudden “jump” in the strain values. To identify cracks, two
14
different approaches were employed.
In the first approach, visual inspection was
conducted and then the cracks were measured using Demec guage. To assist crack
detection, acetone was applied onto the specimen surface with a small piece of cotton.
This way, fine crack could be more easily revealed [Christopher et al (2007)].
Qi et al (2003) used image analysis and modified Weibull technique to measure plastic
shrinkage of restrained slab specimen.
This provides a systematic approach for
quantifying the effect of fibre reinforcement on plastic shrinkage cracking. This method
describes how an image analysis technique is implemented to rapidly extract pertinent
crack width information along a predetermined grid system. Statistical interpretation of
the collected crack widths is performed using either a standard or modified Weibull
distribution function. The process of image analysis included image acquisition, image
processing, crack feature determination, crack feature measurement and Crack width data
analysis.
Thus by using a semi-automated image analysis technique and statistical
approach, the plastic shrinkage cracking of fibre reinforced concrete has been
characterized [C. Qi et al (2003)].
2.2.2.2. Effects of Different Fibres on Plastic Shrinkage
As stated previously, there is a wide verity of fibres that are being used to control plastic
shrinkage cracking of concrete. There have been significant efforts to evaluate and
compare the performance of different types of fibres and their parameters tested under
similar conditions. In 1990, Isabel and Zollo investigated restrained drying shrinkage of
Fibre Reinforced Concrete by experimental program.
Synthetic fibrous concrete
(SNFRC) with polypropylene and acrylic fibres and nonfibrous (control) samples were
tested. The tests were designed to demonstrate the ability of the fibres, (in this case,
applied at low volume percentage) to control cracking and reduce shrinkage [Isabel
Padron et al (1990)].
15
After conducting the experimental program they concluded that the use of relatively fine
(between 5 and 100 denier) polypropylene fibres 19 mm. (3/4 in.) long, and of acrylic
material 10 mm. (3/8 in.) long can
a) Reduce shrinkage for each of the two concrete matrixes tested, and
b) Reduce the total crack area for each of the two concrete matrixes tested.
The amount or percentage reduction in both shrinkage and crack surface area varies
directly with the percent of fibre volume added for the mortar specimens using acrylic
fibres [Isabel Padron et al (1990)].
Shah et al (2004) compared the performance of different fibre types, fibre blends, and
welded-wire fabric (WWF) in their ability to prevent and control drying-shrinkage
cracking. He used flat end steel, hooked end steel, crimped and profiled steel, crimped,
monofilament and multifilament polypropylene fibres at volume fraction of 0.125 to 1%
and steel welded-wire fabric. Among these fibres flat end 30 mm. (1.18 in.) fibre was
found most efficient at all fibre percentage. The advantage of this fibre type is especially
obvious for the lower fibre volumes of 0.125 and 0.25%. In the case of the fibre volume
of 0.25%, no difference in cracking age can be found among the remaining fibre types.
Certain reinforcement types stand out due to the fact that they do not significantly
improve or increase the cracking age compared to the plain concrete mixture. These are
the fibres: Profiled 20 mm (0.8 in) (in Vf = 0.125%), Crimped, PP 50 mm (2 in.) (in Vf =
0.3% and Vf = 0.6%), and the WWF. He noted that the age at which first crack are
formed increases with increasing fibre volume in all cases [Shah et al (2004)].
Naaman (2005), studied the effect of four synthetic fibres and one metallic fibres
(polypropylene, polyvinyl alcohol (PVA), high-density polyethylene (HDPE), carbon,
and, flexible metallic fibres (FMF),) at volume fractions varied from 0.05 to 0.4% and
noticed reduction in total crack area and total crack length accompanied by a significant
decrease in maximum crack widths compared with plain concrete when 0.1% volume
fraction of fibres was used. Increasing the fibre volume fraction from 0.1 to 0.4%
16
slightly improves the plastic shrinkage cracking resistance of fibre-reinforced
cementitious composites.
The direction of the cracks was generally normal to the
longitudinal axis of the specimens and cracks were randomly distributed along the whole
length of specimen.
He also noticed that fibrillated polypropylene fibres were less
effective in controlling plastic shrinkage cracking compared with monofilament
polypropylene fibres when used at 0.1%, however, when the volume fraction of fibre is
increased to 0.4%. The total plastic shrinkage cracking decreases from 45.432 to 5.9175
mm² (0.0704 to 0.0091 in².) when the volume fraction of fibrillated polypropylene fibre
increases from 0.1 to 0.4% [Naaman et al (2005)].
Saleh H. (2006) conducted an extensive experimental program to investigate the
influence of adding POF on the plastic cracks, drying shrinkage, under laboratory and
actual hot-dry condition that normally prevails in the Kingdom of Saudia Arabia. After
being exposed to the field condition for one hour, no cracks appeared in any of the POF
prisms.
This is clear evidence that POF had a great effect in arresting the plastic
shrinkage cracks. It was seen that under both curing conditions, addition of POF to the
concrete mix resulted in increasing the rate of shrinkage at the beginning of the
measuring period and also increased the ultimate shrinkage strain. The increase in the
ultimate strain under laboratory conditions was 17% whereas under field condition was
53% [Saleh H. Alsayed (2006)].
Chen (2008) studied the effectiveness of using small amounts of chopped baler twine to
control the restrained plastic shrinkage cracking of portland cement mortar.
To
determine the influence of baler twine fibre type, length and volume fraction on their
performance, two types of baler twine ( one composed of strands with circular cross
section, the other composed of flat band shape strands) in two lengths; 19 mm and 38
mm. (0.748 and 1.5 in.) and three volume fractions; 0.05%, 0.1%, and 0.3% were
evaluated. Test results indicate that both types of baler twine are capable of controlling
restrained plastic shrinkage cracking to some extent, but are not as effective as fibrillated
polypropylene. Compared with plain specimens, the total crack area was reduced by
95.3, 77.5 and 38.7% when 0.3% volume fraction of 38 mm fibrillated polypropylene,
17
band shape baler twine and circular baler twine fibres, respectively, were added. Free
plastic shrinkage was significantly reduced only when long fibre lengths (38 mm) and
high volume fractions (0.3%) were used [Ying Chen (2008)].
Various studies have been conducted to investigate the effect of fibre dosage on the
shrinkage and drying cracking of PPFRC. All of these showed a significant reduction in
cracking for smaller volume fraction of fibres.
Alhozaimy et al (1995) conducted drying shrinkage test on PPPFRC specimen with
0.05%, 0.1%, and 0.2% volume content on two different lengths of fibres. He concluded
that Polypropylene fibres reduce the total plastic shrinkage crack area and maximum
crack width at 0.1 percent fibre volume fraction of 19 mm. (0.75 in.) fibre. On the
average, 19 mm. (0.75 in) fibres had 13, 57, and 55 percent less crack areas than 13 mm.
(0.5 in.) fibres at 0.05, 0.1, and 0.2 percent fibre volume fractions, respectively. The
maximum crack widths with 19 mm. (0.75 in.) fibres were, on the average, 47, 33, and 36
percent less than those for 13 mm. (0.5 in.) fibres at 0.05, 0.1 and 0.2 percent fibre
volume fractions, respectively [Alhozaimy et al (1995)].
Saeed Ahmed et al (2006) studied the Polypropylene fibres as a way to reduce plastic
shrinkage cracking. The results showed that by using about 0.35% fibres by volume
reduced plastic shrinkage cracking to such an extent that no cracks could be observed and
lower volumes i.e. 0.15 to 0.20% visibly restrained the crack width compared to samples
that were not fibre reinforced. The shrinkage cracking is reduced by 83 to 85% by
addition of fibres upto 0.35% and 0.50 % [Saeed Ahmed et al (2006)].
Collins et al (2008) studied effects of the volume fraction of polypropylene fibres on the
drying shrinkage of hardened concrete made with OPC and slag-blended cement binders.
Different volume fractions of PP fibres ranging from 0.05 to 0.5% have been tested. The
study showed that PP fibre specimens exhibited higher total shrinkage strains compared
with the reference mixture PC with no fibre until the age of 56-days.
The drying
shrinkage of concrete mixture with 0.5% fibre vol. fraction, cured for 1-day and 7days
18
was higher than that of the reference mixture PC by 15% and 22% at an age of 56-days
[F. Collins et al (2008)].
Naaman (2005), Alhozaimy (1995), and Wu (2001) studied the effects of different other
fibres on the plastic shrinkage of PPFRC.
•
Effect of Fibre Length
Alhozaimy concluded that longer fibres [19 mm (0.75 in.)] generally performed better
than shorter ones [13 mm (0.50 in.)]; however, at certain volume fractions, the effect of
fibre length was not statistically significant [Alhozaimy et al (1995)].
Naaman also investigated three different lengths of polypropylene fibres; 12.7, 19.05, and
25.4 mm (0.5, 0.75, 1 in. ) in his study and found that only a slight improvement in
performance is achieved in specimens with longer fibres, that is, a higher aspect ratio
[Naaman et al (2005)].
•
Effect of Fibre Form
Naaman found that at 0.1% fibre volume fraction, fibrillated polypropylene fibres were
less effective in controlling plastic shrinkage cracking compared with monofilament
polypropylene fibres. This disadvantage almost vanishes, however, when the volume
fraction of fibre is increased to 0.4%. The total plastic shrinkage cracking decreases from
45.432 to 5.9175 mm² (.0704 to .0091 in²) when the volume fraction of fibrillated
polypropylene fibre increases from 0.1 to 0.4% [Naaman et al (2005)].
•
Effects of fibre diameter
Better efficiency in reducing plastic shrinkage cracking is achieved with finer fibres. At
0.1% volume fraction, the total crack area of specimens with fibres of diameter 0.1 mm
(0.0039 in.) was 32.183 mm² (0.0498 in²), while the specimen with fibres of diameter
0.04 mm (0.00157 in.) was 1.936 mm² (0.00299 in²), almost 16 times smaller. This
observation was also confirmed when other small-diameter fibres were used, such as
19
carbon fibres. It is concluded that plastic shrinkage cracking depends greatly upon fibre
diameter [Naaman et al (2005)].
•
Effect of Elastic Modulus of fibres
Naaman studied the effect of Modulus of Elasticity of fibres on plastic shrinkage and
found no significant influence on the shrinkage of concrete [Naaman et al (2005)].
•
Effect of Aspect Ratio of fibres
The proportion between length and diameter or equivalent diameter is an important fibre
parameter defined as the fibre aspect ratio. In case of Polypropylene fibres, the fibre
aspect ratio does not influence plastic shrinkage cracking however for Polyvinyl Alcohol
Fibres; fibre aspect ratio seems to be a significant factor for controlling plastic shrinkage
cracking. The total crack area decreases drastically from 32.183 to 1.913 mm² when the
fibre aspect ratio increases from 120 to 300 [Naaman et al (2005)].
•
Effect of Geometry of Fibres
Wu (2002) investigated the effect of geometry of fibres on the shrinkage cracking of
cement mortars using three different forms of polypropylene fibres namely, fibre made in
the drawing-wire technique, fibres made in fibrillated film technique and Y-shaped
fibres. By using 0.05%, 0.1% and 0.15% of fibre contents it was found that the geometry
(cross-section) shape of Y-PP fibre has a better effect on the drying shrinkage cracking
than that of DW-PP fibre. In the present study, the order of reduction in drying shrinkage
cracking is Fibrillated fibre < Y-shaped fibre < Drawing-wire fibre. Especially when
0.10% or more DW-PP fibres are added into cement mortar, drying shrinkage cracking
can be avoided [Wu et al (2002)].
Shah (2004) compared the performance of four different forms of steel fibres, three
different forms of polypropylene fibres and welded-wire fabric in their ability to prevent
and control drying-shrinkage cracking and found that the fibre Flat End [30 mm (1.181
20
in)] is the best-performing reinforcement, concerning age of first crack and maximum
crack width. This is valid for all investigated fibre volumes [Shah et al (2004)].
2.3.
HAREDENED PPFRC
Concrete gains strength as it gets hardened.
The process of gaining strength is
accompanied by evolution of heat of hydration upon curing. The strength of concrete is a
function of time. It gains strength as it gets old up to a certain specified age. The
strength of the fibre reinforced concrete can be measured in terms of its maximum
resistance when subjected to compressive, tensile, flexural and shear stresses either
individually or combined. With the increasing use of fibre reinforced concrete as a
structural material, more information on its mechanical properties was needed.
Researchers have done significant work for establishing the impact of different fibres on
the mechanical properties of fibre reinforced cementitious composites. Conclusions of
some reports and researches on compressive strength, splitting tensile strength and
flexural strength are presented under:
2.3.1. Compressive Strength of PPFRC
The effect of polypropylene fibre on the compressive strength of concrete has been
discussed in many studies and resulted that polypropylene fibres either decrease or
increase the compressive strength of concrete, but overall effect is negligible in many
cases. Many researchers have reported no or a very small influence of small volume
fraction (from 0.05% to 0.5%) of polypropylene fibres on compressive strength of Fibre
Reinforced Concrete, [Naaman et al (1985), Alhozaimy et al (1996), Vikrant et al (2012),
Saeed Ahmed et al (2006)] while some of the researches have shown a significant
increase in the compressive strength on fibre reinforced concrete. Ziad et al concluded
that Polypropylene fibres had a relatively small favorable effect on compressive strength
of concrete when 12 mm (1/2 in.) long fibres were used[Ziad Bayasi et al (1993)]. Song
et al noted an enhancement of approximately 6% when used polypropylene fibres at a
fibre content of 0.6 kg/m³ (0.037 lb/ft³)[Song et al (2005)]. Mtasher et al found increase
21
in the compressive strength of concrete because of presence of fibres in the concrete mix.
The investigation resulted that the Polypropylene fibre inclusions in amount of 0.4% and
1.5% increased the compressive strength up to 11% and 56% respectively [Rana A.
Mtasher et al (2011)]. Ahmed et al noted that polypropylene fibres when used in higher
dosage (0.55% and 0.6%) decreased the 28 days compressive strength of concrete by 35% of that of plain concrete [Saeed Ahmed et al (2006)].
2.3.2. Tensile Strength of PPFRC
Brittle matrices, such as plain mortar and concrete, lose their tensile load-carrying
capacity almost immediately after formation of the first matrix crack (Figure 2.5). The
addition of fibres in conventional fibre reinforced concrete (FRC) can increase the
toughness of cementitious matrices significantly; however, their tensile strength and
especially strain capacity beyond first cracking are not enhanced [Gregor Fischer (2004)].
The tensile strength of concrete is only about 10 % of its compressive strength. It is clear
that addition of fibres to a concrete mixture is beneficial to the tensile properties of
concrete.
The fibres act as crack arresters in the concrete matrix prohibiting the
propagation of cracks in plastic state and propagation of cracks in hardened state. Once
the splitting occurred and continued, the fibres bridging across the split portions of the
matrix acted through the stress transfer from the matrix to the fibres and, thus, gradually
supported the entire load. The stress transfer improved the tensile strain capacity of the
fibre-reinforced concrete and, therefore, increased the splitting tensile strength of the
reinforced concretes over the unreinforced control counterpart.
Vikrant et al studied the effect of length of fibre on the split tensile strength of fibre
reinforced concrete and observed that, the split tensile strength of fibre reinforced
concrete was dependent on length of fibre used. By addition of longer length fibre, the
split tensile strength increases. Use of 24 mm (0.94 in) long fibre with same volume of
fraction gives maximum split tensile strength over fibre 15 mm (0.59 in) and 20 mm
(0.787 in) cut length. The overall effect of 24 mm long fibre when used in fibre content
22
of 0.25% of weight of cement was that, it improved the split tensile strength of concrete
by 72% [Vikrant et al (2012)].
Ahmed et al studied that the tensile strength of concrete increases linearly with addition
of fibres up to about 0.40% after which the tensile strength decreases with addition of
more fibres. The tensile strength increases about 65%~70% up to 0.40% after which it
decreases. Tensile strength is increased due to bridging mechanism of polypropylene
fibres and after certain time it reduced the bond strength between concrete ingredients so
results in quick failure as compared to less volumes of fibres. Song et al noted an
increase of 10% in the split tensile strength of fibre reinforced concrete at the fibre
dosage of 0.6kg/m³(0.037 lb/ft³ ).[ Saeed Ahmed et al (2006), Song et al (2005)].
One the other hand, Xing et al (2004) investigated the mechanical properties of
polypropylene fibre reinforced concrete and found that a low content of polypropylene
fibre [0.91 Kg/m³ (0.056 lb/ft³)] slightly decreased the tensile strength of FRC than that
of plain concrete [Xing et al (2004)].
2.3.3. Flexure Strength of PPFRC
Flexure strength is one of the measures of tensile strength of concrete. It is the ability of
a beam or slab to resist failure in bending. It is measured by loading un-reinforced
concrete beams with a span three times the depth. The flexural strength is expressed as
“Modulus of Rupture” (MR) in psi.
Flexural MR is about 12 to 20 percent of
compressive strength. However, the best correlation for specific materials is obtained by
laboratory tests.
Ziad et al studied the effect of length and volume fraction of polypropylene fibre on the
flexural behavior of PPFRC by characterising the post-peak flexural resistance under four
point loading. It was found that, for volumes equal to or less than 0.3 percent, 19 mm
(3/4 in.) long fibres were more favorable for enhancing the post-peak resistance. For 0.5
percent volume, 12 mm (1/2 in.) long fibres were more effective [Ziad Bayasi et al,
(1993)].
23
Alhozaimy et al investigated the effect of different volume fractions of polypropylene
fibre and different types of binders on the flexure strength and toughness of the
composite using the test procedure designed by ASTM C78 for the Two-Point Loading
and found that at lower volumetric fractions, the fibre has no effect on the flexural
strength of FRC; however the binder compositions has significant effect on the flexural
toughness of FRC. Polypropylene fibres affect the flexural toughness significantly. On
the average, the addition of 0.1%, 0.2%, and 0.3% volume fraction of fibres increases the
flexural toughness by 44%, 271% and 387%, respectively [Alhozaimy et al (1996)].
Ahmed et al found that the behavior of concrete in flexure seems to be identical with
polypropylene fibre reinforced concrete as that in tensile strength. There is about 80%
increase in flexure strength by adding 0.20% fibres in concrete after which strength starts
reducing with further increment in fibre ratios [Saeed Ahmed et al (2006)].
Mtasher et al investigated the effects of different volume fraction of polypropylene fibre
on the mechanical properties of FRC and found that when polypropylene fibres was used
in amount of 0.4% and 1.5% (on cement content), the increase of flexural strength 24.6%
and 85% respectively [Rana A. Mtasher et al, (2011)].
24
Table 2.1
A compilation of mechanical properties of commonly used fibres
in concrete materials [ACI 544.5R (2010)]
Equivalent
Type of Fibre Diameter
(mm)*
0.02 to 0.35
Acrylic
0.0015
to
Asbestos
0.02
Cotton
0.2 to 0.6
Specific
Gravity
(Kg/m³)**
1100
Tensile
Strength
(MPa)***
200 to 400
3200
1500
600 to 1000
400 to 700
1000
to
Glass
0.005 to 0.15
2500
2600
0.008
to
1000
to
Graphite
0.009
1900
2600
3500
to
Aramid
0.01
1450
3600
Nylon
0.02 to 0.40 1100
760 to 820
Polyester
0.02 to 0.40 1400
720 to 860
Polypropylene 0.02 to 1.00 900 to 950 200 to 760
Polyvinyl
alcohol
0.027 to 0.66 1300
900 to 1600
Carbon
1400
4000
Rayon
0.02 to 0.38 1500
400 to 600
Basalt
0.0106
2593
990
Polyethylene
0.025 to 1.0 960
200 to 300
Sisal
0.08 to 0.3
760 to 1100 228 to 800
Coconut
0.11 to 0.53 680 to 1020 108 to 250
Jute
0.1 to 0.2
1030
250 to 350
Steel
0.15 to 1.00 7840
345 to 3000
Young's
Modulus
(GPa)
2
Ultimate
Elongation
(%)
1.1
83 to 138
4.8
1.0 to 2.0
3.0 to 10.0
70 to 80
1.5 to 3.5
230 to 415 0.5 to 1.0
65 to 133
4.1
8.3
3.5 to 15
2.1 to 4.0
16 to 20
11 to 13
5.0 to 25.0
23 to 40
230 to 240
6.9
7.6
5
11 to 27
2.5 to 4.5
26 to 32
200
7 to 8
1.4 to 1.8
10 to 25
2.56
3
2.1 to 4.2
14 to 41
1.5 to 1.9
4 to 10
* 1 mm = 0.0393 in, ** 1 Kg/m³ = 0.0624 lb./ft³, ***1 MPa = 145 psi
25
Table 2.2
Properties of different types of polypropylene fibres [S.K. Singh
(2010)]
Fibre Type
Length
(mm)*
Daimeter
(mm)*
Tensile
Strength
(Mpa)**
Modulus of
Density
Elasticity
(kg/m³)***
(Gpa)
Monofilament
Microfilament
Fibrillated
30-50
12-20
19-40
0.30-0.35
0.05-0.20
0.20-0.30
547-658
330-414
500-750
3.50-7.50
3.70-5.50
5.00-10.00
* 1 mm = 0.0393 in, **1 MPa = 145 psi, *** 1 kg/m³ = 0.0624 lb./ft³
26
0.9
0.91
0.95
Length, Diameter or Perimeter
Geometrical
Section
Shape
Fibre
Characteristics
Figure 2.1
Circular, elliptical,
square, rectangle, triangle
flat....
Smooth, deformed, indented,
etched, crimped, coilled, twisted,
with end paddles, end hooks, end
buttons, 2D, 3D,...
Mechanical
Strength, elastic modulud, transverse
modulud,stiffness, ductility, elongation to failure
Physical/
Chemical
Density, surface roughness, chemical stability, fire
resistance, non-reactivity with cement...
Material
- Natural organic: wood, sisal, jute, bamboo...
- Natural mineral: asbestos, rock, wool...
- Man-made: steel, polymers (synthetic), glass,
carbon, metallic,...
Main characteristics of fibres [Naaman et al (2006)]
Composite
Fibre
Matrix
Cement Paste:
-Cement
-Water
-Addditive and Admixtures
Aggregates:
Coarse and fine
Others:
Recycled wastes, unwanted
materials, organics, woods
Figure 2.2
Composite model of FRC with two main components, namely fibre and
matrix [Naaman et al (2006)]
27
Figure 2.3
Simplified general classification of FRC composites based on their
tensile stress-strain response [Naaman et al (2007)]
Figure 2.4
Typical stress-strain or elongation curve in tension up to complete
separation: (a) Conventional strain-softening FRC composites; (b) Strainhardening FRC composites [Naaman et al (2007)]
28
Figure 2.5 Schematic stress-strain behaviour of cementitious matrix in tension
[Gregor Fischer (2004)]
29
CHAPTER 3
EXPERIMENTAL PROGRAM
3.1 GENERAL
This chapter provides a detailed description of the materials used in the experimental
program and experimental methods used in this study.
The experimental program
consisted of laboratory tests on plain concrete and polypropylene fibre reinforced
concrete (PPFRC) to characterize the properties such as flow ability in fresh state, early
age plastic shrinkage and mechanical properties in hardened state. For this purpose total
of seven (7) concrete mixtures were cast with one control mix (plain concrete) and six
PPFRC mixes. The PPFRC mixes were for two different length of fibre Lf (25 mm and
38 mm) and the different volume fraction of fibre Vf were 0.3%, 0.6% and 0.8%.
The materials, mix design (mixture proportions), casting, curing, test methods and
procedures for workability of PPFRC, tests for plastic shrinkage of PPFRC and tests for
selected mechanical properties of hardened concrete are described in detailed in the
respective sections.
3.2 MATERIALS
3.2.1. Cement
Ordinary Portland (ASTM Type-I) cement is used for this study.
3.2.2. Aggregates
The coarse aggregate used in this experimental program is found at Hub Chowk near
Karachi and the fine aggregate is found at the Super Highway, Karachi. The coarse
aggregate passing through sieve #2 and retained over sieve #3 is used. Whereas fine sand
passing through sieve #16 and retained on sieve #20 was used as fine aggregate.
30
3.2.3. Water
Ordinary tap water which is being supplied by Karachi Water and Sewerage Board was
used for mixing of concrete ingredients and also for other experimental work including
washing of equipment, curing of specimen etc.
3.2.4. Fibre
Fibrillated polypropylene fibres (PPF) with two different lengths were used in different
volume percentage. The fibre and the material specifications were provided by the
Matrixx Company. The fibrillated polypropylene fibres are composed of film sheets
which are cross linked by fine fibre along their length as shown in Figure 3.1. These
fibres are manufactured in chicken mesh form and then cut into desired length. The two
different lengths of PPF used in this study were 25 mm and 38 mm (see Figure 3.2). The
physical and mechanical properties of PPF are shown in Table 3.1.
3.2.5. Admixture
Super plasticizer was used to increase the workability of freshly prepared fibre reinforced
concrete.
3.3 MIX DESIGN
A suitable concrete mix design was established on the basis of preliminary testing of
mortar cubes having cement to sand ratio of 1:2.75 and w/c ratio of 0.48. Twelve number
of 2”x2” cubes were cast and cured in water tank and then tested under compression
using Universal Testing Machine at a loading rate of 60 psi/min. The strength- time
curve was developed for 28 days of curing. (See Figure 3.3) Each point on strength-time
curve is an average of three replicate cube specimens. Note that the 28 day strength is in
excess of 3000 psi.
31
The mixing for concrete was done in rotary drum mixer at a mixing rate of 40 rpm.
Pictorial view of the mixer is shown in Figure 3.4. The drum was previously moistened
by spraying just enough water to moist the inner surface of the drum. The mixing
sequence used for all mixtures was as follows:
• Add the fine aggregate (sand) to the mixer and mix for 30 seconds
• Add the coarse aggregate to the mixer and mix for 30 seconds
• Add the fibres and mix for 3 minutes (not done the plain concrete)
• Add 50% of the adjusted water and mix for 30 seconds
• Add all the cement to the mixer and mix for 30 seconds
• Add admixture into the balance of the water, introduce into the mixer and mix
for 4 minutes
• Let the mixed PPFRC be idle for 2 minutes and then mix for 4 additional
minutes
After mixing, the concrete was placed into lubricated moulds and vibrated
externally. A smooth steel trowel was used to finish the fresh concrete. The mix
proportions of concrete mixtures are shown in Table 3.2.
3.4 TESTS FOR WORKABILITY OF FRESH PPFRC
Six standard test methods were used to study the workability of PPFRC in terms of flow
ability. These being Standard Slump test, Inverted Slump Test (Compacting Factor Test),
Flow Table Test, J-Ring Test, L-Box Test and V-Funnel Test. All these tests were
performed on the same batch of concrete for the purpose of homogeneity and the results
obtained thus were compared and calibrated. The complete experimental matrix for
workability tests is given in Table 3.3. Freshly prepared PPFRC is shown in Figure 3.5.
3.4.1. Standard Slump Test (ASTM C143)
The slump test is the most well-known and widely used test method to characterize the
workability of fresh concrete. The inexpensive test, which measures consistency, is used
on job sites to determine rapidly whether a concrete batch should be accepted or rejected.
32
The test method is widely standardized throughout the world, including in ASTM C143
in the United States and EN 12350-2 in Europe. [Eric et al (2003), ASTM C143 (2000)]
The apparatus consists of a mould in the shape of a frustum of a cone with a base
diameter of 203 mm (8 inches), a top diameter of 101 mm (4 inches), and a height of 305
mm (12 inches). The assembly is shown in Figure 3.6. During this test, the mould is
filled with concrete in three layers of equal volume. Each layer is compacted with 25
strokes of a tamping rod. The slump cone mould is lifted vertically upward and the
change in height of the concrete is measured.
Three types of slumps are commonly encountered, as shown in Figure 3.7. The only type
of slump permissible under ASTM C143 is frequently referred to as the “true” slump,
where the concrete remains intact and retains a symmetric shape. A zero slump and a
collapsed slump are both outside the range of workability that can be measured with the
slump test. Specifically, ASTM C143 advises caution in interpreting test results less than
12 mm (½ inch) and greater than 228 mm (9 inches). If part of the concrete shears from
the mass, the test must be repeated with a different sample of concrete. A concrete that
exhibits a shear slump in a second test is not sufficiently cohesive and should be rejected
[Eric et al (2003)].
3.4.2. Compacting Factor Test (BS 1811-103)
The compaction factor test measures the degree of compaction resulting from the
application of a standard amount of work. The test was developed in Britain in the late
1940s and has been standardized as British Standard 1881-103 [Eric et al (2003), BS
1881-103 (1993)].
The apparatus, which is commercially available, consist of a rigid frame that supports
two conical hoppers vertically aligned above each other and mounted above a cylinder, as
shown in Figure 3.8. The top hopper is slightly larger than the bottom hopper, while the
cylinder is smaller in volume than both hoppers. To perform the test, the top hopper is
filled with concrete but not compacted. The door on the bottom of the top hopper is
33
opened and the concrete is allowed to drop into the lower hopper. Once all of the
concrete has fallen from the top hopper, the door on the lower hopper is opened to allow
the concrete to fall to the bottom cylinder. A tamping rod can be used to force especially
cohesive concretes through the hoppers. The excess concrete is carefully struck off the
top of the cylinder and the mass of the concrete in the cylinder is recorded. This mass is
compared to the mass of fully compacted concrete in the same cylinder achieved with
hand rodding or vibration. The compaction factor is defined as the ratio of the mass of
the concrete compacted in the compaction factor apparatus to the mass of the fully
compacted concrete. The standard test apparatus, described above, is appropriate for
maximum aggregate sizes of up to 20 mm. A larger apparatus is available for concretes
with maximum aggregate sizes of up to 40 mm [Eric et al (2003)].
3.4.3. Flow Table (ASTM C1437)
This test provides information on filling ability (flowability) and passing ability (for a
stable mix, high flowability tracks with passing ability) [ASTM C1437 (1999), Technical
Bulletin 1506].
The apparatus consists of standard Abram’s cone [ASTM C143 (2000)] and Slump flow
board which is a non-absorbent rigid plate (coated plywood, plastic, metal or similar
material) measuring at least 1 meter square (39 in. per side) as shown in Figure 3.9. In
general, the slump flow test is very similar to the standard slump test but it is used to
measure the horizontal spread of concrete cone specimen. The Abram’s cone is placed in
the centre of the slump flow board, either in the normal orientation (large opening down)
or inverted (small opening down).
It is filled in one lift (no rodding or other
consolidation) and then the cone is then raised in 3 ±1 seconds to a height of 230 ±75 mm
(9 ±3 in.), allowing the fluid concrete to flow onto the slump flow board. The slump flow
is the diameter of the resulting concrete “patty” obtained from the average of measuring
the greatest diameter and diameter perpendicular to this direction. Large differences
between the two diameters indicate a non-level surface, which must be corrected [ASTM
C1437 (1999), Technical Bulletin 1506].
34
3.4.4. J-Ring Test (ASTM1621)
The J-ring test extends common filling ability test methods to also characterize passing
ability. The J-ring test device can be used with the slump flow test. The J-ring, as shown
in Figure 3.10, is a rectangular section (30 mm by 25 mm) open steel ring with a 300 mm
diameter. Vertical holes drilled in the ring allow standard reinforcing bars to be attached
to the ring. Each reinforcing bar is 100 mm long. The spacing of the bars is adjustable,
although 3 times the maximum aggregate size is typically recommended. For fibrereinforced concrete, the bars should be placed 1 to 3 times the maximum fibre length
[Eric et al (2003)].
To conduct the J-ring test in conjunction with the slump flow test, the slump cone is
placed in the centre of the J-ring and filled with concrete. The slump cone is lifted and
concrete is allowed to spread horizontally through the gaps between the bars [Eric et al
(2003), ASTM 162 (2011)].
Various interpretations of the test results have been suggested. The measures of passing
ability and filling ability are not independent. To characterize filling ability and passing
ability, the horizontal spread of the concrete sample is measured after the concrete passes
through the gaps in the bars of the J-ring and comes to rest. Also, the difference in height
of the concrete just inside the bars and just outside the bars is measured at four locations.
The smaller this difference in heights is, the greater the passing ability of the concrete
will be. Alternatively, the horizontal spread with and without the J-ring can be compared
as a measure of passing ability [Eric et al (2003), ASTM 162 (2011)].
3.4.5. L-Box Test
The L-box test measures the filling and passing ability of self-compacting concrete.
Originally developed in Japan for underwater concrete, the test is also applicable for
highly flowable concrete [Eric et al (2003)].
35
As the test name implies, the apparatus consists of an L-shaped box, shown in Figure
3.11. Concrete is initially placed in the vertical portion of the box, which measures 600
mm in height and 100 mm by 200 mm in section. A door between the vertical or
horizontal portions of the box is opened and the concrete is allowed to flow through a line
of vertical reinforcing bars and into the 700 mm long, 200 mm wide, and 150 mm tall
horizontal portion of the box. In the most common arrangement of reinforcing bars, three
12 mm bars are spaced with a clear spacing of 35 mm. Generally, the spacing of the
reinforcing bars should be three times the maximum aggregate size. It should be noted
that various dimensions for the L-box have been used and no one set of dimensions is
considered official; however, the dimensions described above seem to be the most
common [Eric et al (2003)].
After the concrete comes to rest in the apparatus, the heights of the concrete at the end of
the horizontal portion, H2, and in the vertical section, H1, are measured. The blocking
ratio, H2/H1, for most tests should be 0.80 to 0.85. If the concrete being tested is truly
self-levelling, like water, then the value of the blocking ratio will be unity. Segregation
resistance can be evaluated visually. A concrete sample with coarse aggregate particles
that reach the far end of the horizontal part of the box exhibits good resistance to
segregation. The L-box can be disassembled after the concrete has hardened [Eric et al
(2003)].
While the test does give valuable information about filling and passing ability, and to a
lesser extent, segregation resistance, the test is not as simple as the slump flow test.
Since there are no standardized dimensions, results from different test apparatuses cannot
be compared directly [Eric et al (2003)].
3.4.6. V-Funnel Test
The V-funnel test is used to measure the filling ability of concrete and can also be used to
judge segregation resistance. The test method is similar to the concept of the flow cone
test used for cement paste.
36
The test apparatus, shown in Figure 3.12 consists of a V-shaped funnel with a height of
425 mm (16.75 inches) a top width of 490 mm (19.29 inches), a bottom width of 65 mm
(2.55 inches), and a thickness of 75 mm (3 inches). At the bottom of the V-shape, a
rectangular section extends downward 150 mm ( inches). The entire funnel is filled with
concrete without tamping or vibration. The door at the bottom of the funnel is opened
and concrete is allowed to flow out of the funnel and into a bucket. The flow time for all
of the concrete to exit the funnel is recoded as a measure of filling ability. Further, nonuniform flow of concrete from the funnel suggests a lack of segregation resistance [Eric
et al (2003)].
3.5 TESTS FOR PLASTIC SHRINKAGE OF FRESH PPFRC
A standard test method for measuring the length change of hardened mortar or concrete
specimens was introduced in ASTM C157. However, it is still a challenge to measure the
early-age shrinkage of concrete, while it is still in a plastic state, and no standardized
method exists to evaluate free (unrestrained) plastic shrinkage [ASTM C157 (1999),
ASTM C596 (2000)].
This test gives a measure of the amount of drying shrinkage of hardened mortar and
concrete in terms of change in length. The standard specimen size is 4”x4”x11 ¼”.
Before casting, the polyethylene sheets were placed on the inside of the moulds to
prevent any loss of water from the mix (see Figure 3.13).
After casting, two
identification marks were drawn on the top surface of the specimen at some suitable
distance in order to measure length changes at the required time intervals. This was done
by embedding two metallic nails or pins on the longitudinal axis of each specimen’s top
surface, separated longitudinally by a distance of approximate 8 inches (200 mm).[ Chen
(2008)]. Figure 3.14 shows the standard shrinkage prism with thumb tacks over it. A
digital calliper with a precision of 0.01 mm (0.000393 in) was used to measure the
distance between the indentations on the thumb tacks initially and after the required time
intervals (See Figure 3.15). [ASTM C157 (1999)] A schematic diagram of shrinkage
specimen is shown in Figure 3.16.
37
The initial reading is taken after 24 hours of mixing water with cement and then the
specimen were exposed to natural environment at room temperature.
The calliper
readings are taken after 48, 72 and 96 hours. The length change of any specimen at any
age after the initial calliper reading is computed using the Eq. 3.1 and noted as a percent
increase or decrease in linear dimension to the nearest 0.001 % of the gage length based
on the initial measurement made at the time of removal from moulds. [ASTM C157
(1999)]
∆L = (L – previous L)/G x100
{Eq. 3.1}
Where,
∆L = length change of specimen at any age, %
L = comparator reading of the specimen at known time interval, and
G = the gage length (initial L)
The moisture loss measurements were also done by measuring the weight of 4'' x
4'' x 11 ¼'' specimens at the same time interval. The complete experimental matrix is
given in Table 3.4.
3.6 TESTS FOR MECHANICAL PROPERTIES OF HARDENED
PPFRC
Some of the mechanical properties of PPFRC are considered in this study. These include
Compressive strength, splitting tensile strength and flexure strength. Standard methods
of test for each of the property are described in the following sections. The complete
experimental matrix is given in Table 3.5.
38
3.6.1. Compressive Stress-Strain Curve (ASTM C39)
This test method covers the determination of cylindrical compressive strength of concrete
specimen. The specimens are prepared by pouring freshly mixed concrete into lubricated
cylinders. The mixing procedure is the same as described in Section 3.3 of this report.
Consolidation is done externally over vibrating table for 3-5 minutes. After vibration and
finishing, the moulds are kept at normal atmospheric conditions for 23 ½ ± ½ hours after
which de moulding is done. The specimens are then cured in water tank [ASTM C39
(2001)].
The test is conducted at surface dry condition. The specimens are capped, placed and
seated in the testing machine as described by section 7 of ASTM C39. The specimens are
tested at the age of 7, 14 and 28 days of curing under the Universal Testing Machine
shown in Figure 3.17. This machine applies compressive stress on the cylinder due to the
downward movement of the platen at a constant displacement rate of 0.1 mm/sec. Figure
3.18 shows schematic diagram of the compressive strength test. The load and stroke
measurements are noted from which stress and longitudinal strain values are computed
and plotted for each set of tests [ASTM C39 (2001)]. The strength-time curves for plain
concrete and PPFRC were also obtained for an average of three values and then
compared to each other.
3.6.2. Splitting Tensile Strength of Concrete Cylinders (ASTM C496)
This test method covers the determination of splitting tensile strength of concrete
cylinders. The procedure for preparation of specimens for split cylinder testing is similar
to the procedure described in the Section 3.6.1 of this report.
Figure 3.19 shows schematic diagram of the split tensile strength test. This test method
consists of applying a diametric compressive force along the length of a cylindrical
concrete specimen at a rate that is within a prescribed range until failure occurs. This
loading induces tensile stresses on the plane containing the applied load and relatively
high compressive stresses in the area immediately around the applied load. Tensile failure
39
occurs rather than compressive failure because the areas of load application are in a state
of multi axial compression, thereby having a much higher resistance as compared to
uniaxial compressive strength test result. [ASTM C496 (1996)]
The test was performed in the Universal Testing Machine (see Figure 3.17). The load
and stroke values are recorded by the test machine and the split tensile stresses were
calculated by using the Eq. 3.2.
T=2P/πld
(Eq. 3.2)
Where,
T = splitting tensile strength, psi (kPa),
P = maximum applied load indicated by the testing machine, lbf (kN),
l = length, in. (m), and
d = diameter, in.(m).
Tensile stress-strain and strength-time curves were plotted for plain and PPFRC and then
compared.
3.6.3. Flexure Strength of Concrete Beams (ASTM C78)
This test method covers the determination of the flexural strength of concrete by the use
of a simple beam with third-point loading. The preparation of sample is the same as
described in ASTM C42 [ASTM C42 (1999)].
For the purpose of finding indirect tensile strength of plain concrete and PPFRC, a total
fourteen (14) - 3''x 6''x72'' beams specimens were cast and tested under two point loads.
The section and span of the beam specimens is shown in Figure 3.20. The testing
procedure as described in ASTM C78 implies that the third point loading method shall be
used in the testing and concrete bearing blocks will be employed, which will ensure that
40
forces applied to the beam will be perpendicular to the face of the specimen and applied
without eccentricity. A schematic diagram of test set-up and loading is shown in Figure
3.21 [ASTM C78 (2001)]. The test was performed in the Universal Testing Machine.
The load was applied by the downward movement of the platen. The loading assembly is
shown in Figure 3.22.
The load and displacement data were obtained for each beam specimen and the average
values of replicate specimen were calculated and load-deflection (P-δ) curves were
plotted. From the P-δ curves, the effect of various amount of PPF with different fibre
length on the strength and the post peak deformation capacity was studied.
41
Table 3.1
Polypropylene technical data sheet (MATRIXX)
Compressive Strength (psi)
Flexural strength (psi)
Tensile strength at break (psi)
Elongation at break (%)
Water absorption (%)
Specific gravity
Ignition point
Melting point
Heat & UV stabilization
Thermal conductivity
5,500-8,000
6,000-8,000
4,500-6,000
100-600
Negligible (0.01-0.03)
0.90-0.91
593°C
160 - 170°C
Long Term
2.8 10-4 cal cm/sec cm² °C
Tensile modulus (ksi)
165-225
Compressive modulus (ksi)
150-300
Flexural modulus (ksi @ 170-250
25°C.)
Electrical conductivity
Low
Salt resistance
High
Acid resistance
High
Alkali resistance
100% (alkali proof)
42
ASTM D695
ASTM D790
ASTM D638
ASTM D638
ASTM D570
ASTM C177
ASTM D638
ASTM D695
ASTM D790
Table 3.2
Mix No.
PCC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
PPFRC 0.4-38
PPFRC 0.6-38
PPFRC 0.8-38
Mix proportion of concrete mixtures in Kg/m³
Fibre
Content Fibre
(Kg/m³) Volume
Fraction
(%)
0
3.6
5.4
7.2
3.6
5.4
7.2
0
0.4
0.6
0.8
0.4
0.6
0.8
Fibre
Length
Cement
mm
(Kg/m³)
25
25
25
38
38
38
Fine
Coarse
Agg.
Agg.
(Kg/m³) (Kg/m³)
440
760
970
0.6
525
788
920
0.55
585
788
920
0.55
*added to increase slump value after fibre was added into the concrete
PPFRC Vf (%)-Length of PPF (mm)
1 Kg/m³ = 1.68 lb/ft³
43
w/c
Ratio
SuperPlasticizer
(L/m³)
2.2
5.25
5.25
5.25
5.85
5.85
5.85
Table 3.3
Experimental matrix for workability tests
Standard Slump
Test
Mix No.
Vertical
Slump
Slump
Type
(in)
Compacting
Factor Test
Flow
Table
J-Ring
Test
C.F
Diameter
Diameter
(kg/kg)
(in)
(in)
L- Box
Test
VFunnel
Blocking
Ratio
H₂₂/H₁₁
(in/in)
Flow
Time
(sec.)
PCC
PPFRC 0.425
PPFRC 0.625
PPFRC 0.825
PPFRC 0.438
PPFRC 0.638
PPFRC 0.838
Table 3.4
Description
A
B
Plastic
Shrinkage
Moisture
Loss
Experimental matrix for shrinkage tests
Spacimen
Size
4"x4"x11
1/4"
Specimen
4"x4"x11
1/4"
Specimen
Testing
Age
No. of
Samples
for
Vf=0%
No. of
Samples
for
Vf=0.2%
No. of
Samples
for
Vf=0.4%
Total
specimens
24 hr
3
6
6
15
48 hr
-
-
-
0
72 hr
-
-
-
0
96 hr
24 hr
-
-
-
0
3
6
6
15
48 hr
-
-
-
0
72 hr
-
-
-
0
96 hr
-
-
-
0
44
Results
Length
Change
(∆L)
Weight
loss (%)
Table 3.5
Description
A
B1
B2
Compressive
Strength
Experimental matrix for mechanical properties
Spacimen Testing No. of
No. of
Size
Age
Samples Samples
for
for
Vf=0%
Vf=0.4
%
7 Days
3
6
4"x8"
Cylinders
Indirect
Tension Split
Cylinder
4"x8"
Cylinders
Indirect
TensionBeams
3"x6"
x72"
Beams
14
Days
28
Days
7 Days
14
Days
28
Days
28
Days
Total
No. of
No. of
Samples Samples specimen
for
for
Vf=0.6% Vf=0.8%
6
6
21
3
6
6
6
21
3
6
6
6
21
3
6
6
6
21
3
6
6
6
21
3
6
6
6
21
2
4
45
4
4
Results
14
StressStrain
property
StressStrain
property
P-δ
curves
Figure 3.1
Fibrillated polypropylene fibre
Figure 3.2
Polypropylene fibres of different length
46
Avg. Compressive Strength(psi)
4000
3500
3 days
28 days
14 days
3000
3046
2500
3372.03
3147
2000
1500
Average of 3
replicate
specimen
1000
500
0
0
5
10
15
20
25
30
Time(days)
Figure 3.3
The average compressive strength-time curve of 2”x2” mortar cubes
Figure 3.4
Pictorial view of rotary drum mixer
47
Figure 3.5
Pictorial view of freshly prepared FFRRC
Figure 3.6
Pictorial view of standard slump test apparatus [Eric et al (2003)]
48
Figure 3.7
Types of concrete slump [Eric et al (2003)]
Figure 3.8
Compacting factor test apparatus [Eric et al (2003)]
49
Figure 3.9
Pictorial view of flow table test apparatus [Technical Bulletin 1506]
Figure 3.10
Pictorial view of J-ring test apparatus [Eric et al (2003)]
50
Figure 3.11
Pictorial view of L-box test apparatus [Eric et al (2003)]
Figure 3.12
Pictorial view of V-funnel test apparatus [Eric et al (2003)]
51
Figure 3.13
Pictorial view of shrinkage moulds lined with plastic sheets
Figure 3.14
Pictorial view of shrinkage specimen after casting
52
Figure 3.15
Pictorial view of length measurement instrument
Figure 3.16
Schematic view of standard shrinkage specimen
53
Figure 3.17
The universal testing machine
Figure 3.18
Schematic diagram of the compressive strength test setup
54
Figure 3.19
Schematic diagram of the tensile split test setup
Figure 3.20
Flexure test beam profile and section
55
Figure 3.21
Schematic diagram for flexure test
Figure 3.22
Pictorial view of the loading assembly for two-point flexure test
56
CHAPTER 4
RESULTS AND DISCUSSION
4.1.
INTRODUCTION
The fabrication, curing of the test specimens was presented in Chapter 3. In this
chapter, the results of laboratory tests are presented and discussed. These include
results of workability tests of fresh concrete using six (6) different test procedures,
results of early age shrinkage tests, results of compression tests at test ages of 7, 14
and 28 days respectively, results of split cylinder tests at test ages of 7, 14 and 28 days
respectively, and results of beam flexural tests at 28 days.
4.2.
WORKABILITY OF FRESH PPFRC
For the workability of fresh concrete, the six (6) tests used were traditional Slump
Cone Test, Compacting Factor, Flow Table diameter, J-Ring Diameter, L-Box
blockage ratio and V-funnel time tests. These tests were performed on concrete
without polypropylene fibres (PPF) termed as “control” specimens and on
polypropylene fibre reinforced concrete (PPFRC) specimens.
For the PPFRC
specimens, variables included length of polypropylene fibres (lf) and the volume
fraction (Vf) of polypropylene fibres.
The tests results of various fresh properties tests of Plain Concrete (PC) and
polypropylene fibre reinforced concrete (PPFRC) with different volume fraction (Vf)
and length of fibre (Lf) are presented in the Table 4.1.
The PPFRC mixtures were proportioned to give slump values which are needed to
ascertain adequate workability of the fresh concrete to be placed and finished. For all
the concrete mixes having different fibre contents and with different lengths of fibres,
the measured slump is greater than 3 in. (76 mm), which is an acceptable slump
values for the ease of construction and finsishability. For the PPFRC mixtures, in
order to maintain reasonable slump, and approximately similar w/c, the quantity of
cement was increased with increase in amount of chemical admixture as segregation
57
was observed to occur when only water content was increased in order to increase the
workability of the PPFRC mixtures.
Pictorial view of various workability tests are shown in Figure 4.1-4.8. The addition
of polypropylene fibres (PPF) reduced the flow characteristics when L-Box and VFunnel tests were performed for the different mixtures. This is because during mixing
of the concrete, the coarse aggregates damage the fibrillated PPF fibres to some
degree and perhaps do not permit the PPF to fully open into a lattice structure, instead
the PPF open into a network of linked fibre filaments and individual fibres. These
fibres adhere to the cement paste because of their large specific surface area. The
concrete mixtures with polypropylene fibres (PPF) result in lower (reduced) bleeding
and segregation as compared to plain concrete. This is because the PPF help in
maintaining the continuum (holding the concrete together or increasing the
cohesiveness of concrete) and thus reduces the segregation of the coarse aggregates.
The effect of fibre length (Lf) on the vertical slump for different fibre volume
fractions (Vf) is shown in Figure 4.9. It can be seen that greater the fibre length (Lf),
greater is the measured slump. This is because for a fixed volume fraction of PPF in
PPF mixtures, in the concrete, less number of longer fibres will be present as
compared to the shorter length fibres. Fibre population will be smaller in case of
longer fibres which results in larger slumps for the case of longer fibres.
The effect of fibre volume fraction (Vf) on the slump for the two different lengths of
fibres is shown in Figure 4.10. The results indicate an inverse relationship between
the two parameters i.e. the slump (or the workability) decreases with increase in fibre
volume fraction (Vf). This re-affirms the trends reported in the literature in Chapter 2
of this report.
The experimental results show that a relationship does exist between the slump flow
and the compacting factor (Figure 4.11). The compaction factor is parameter which
gives the degree of compaction of the fresh concrete resulting from the application of
a standard amount of work. From regression analysis the coefficient of determination
(R²), is found to be 0.8382, which indicates that high degree of correlation between
the between the slump flow and the compacting factor.
58
The relationship between the slump and diameters from J-Ring and the flow table
tests are shown in Figure 4.12. The straight line regression equation with a coefficient
of correlation of 0.9099 for the data of slump and the J Ring diameter is also shown in
the Figure 4.12. The exponential line equation with a coefficient of correlation of
0.8242 for the data of slump and flow table diameter is also shown in the Figure 4.12.
This indicates that the relationship of slump with J ring diameter is seemingly
stronger than the relationship between slump and the flow table diameter.
4.3.
PLASTIC SHRINKAGE OF FRESH PPFRC
The test procedure for shrinkage test is described in the Chapter 3. The results of the
shrinkage tests performed on the control specimen PC and four different PPFRC
mixtures are shown in Table 4.2. The length measurement was done using a digital
calliper (see Figure 4.13) and then the results were computed using Eq. 3.1. The
results were then plotted against time and then compared.
The graphical
representation of the results is given in Figure 4.14. In general it can be noted that the
shrinkage of both PC and PPFRC mixtures varies greatly in the initial 24 hours and
then gradually reduces with the passage of time. From Figure 4.14, it is evident that
the shrinkage of PC specimens is larger than shrinkage of PPFRC specimens and that
addition of PPF reduces the early age plastic shrinkage of concrete. Among the four
PPFRC mixtures, the PPFRC 0.4-25 is found to be the most efficient in controlling
early age shrinkage as it showed the maximum average shrinkage of 0.106% at 72
hours. The other three mixtures i.e. PPFRC 0.2-25, PPFRC 0.2-38 and PPFRC 0.4-38
showed the maximum average shrinkage of 0.378%, 0.165% and 0.312% respectively.
Here it can be noted that for 25 mm long PP fibre, higher Vf (0.4%) showed better
performance in controlling plastic shrinkage than that of smaller Vf (0.2%). Thus for
25 mm long PP fibre, the early age shrinkage reduces with the increasing Vf.
For the case of 38 mm long PP fibres, plastic shrinkage for the Vf of 0.4% was greater
than for Vf of 0.2%. Higher Vf showed greater plastic shrinkage. A similar trend was
also reported by Collins [F. Collins et al (2008)]. The drying shrinkage of concrete
mixture with 0.5% fiber volume fraction, cured for 1-day and 7days was higher than
that of the plain concrete [F. Collins et al (2008)].
59
The moisture loss rate was also determined for the control PC and four PPFRC
mixtures. The readings of weight of 4” x 4” x 11 ¼” specimens were taken at the
same time interval, when the shrinkage readings were recorded. The results of weight
loss test are presented in Table 4.3 and Table 4.4. The graphical representation of
moisture loss with time is shown in Figure 4.15, which shows the same trend for all
the mixtures as that of shrinkage. The moisture loss is greater for the first 24 hours
and then gradually slows down. It is also clear that the PC showed the least weight
loss of 1.86% at 72 hours as compared to the PPFRC, which may be because of
hydrophobic property of the fibres which enable the water from being absorbed and
so it evaporates at higher rate for the PPFRC. Among the four PPFRC mixtures, the
PPFRC 0.4-38 showed the greatest loss of water i.e. 3.169% at 72 hours. The other
three mixtures, i.e. PPFRC 0.2-25, PPFRC 0.4-25 and PPFRC 0.2-38 showed 2.091%,
1.863% and 2.895% moisture loss at 72 hours respectively.
The slower rate of moisture loss in PPFRC is primarily because of the reason that
presence of fibres in the concrete increase the time to initial and final set of the
concrete and so a slower rate of drying of water from the mix. [S.K.Singh (2010)] To
be more precise, the fibrillated fibres, when mixed in concrete, open into a network of
linked fibre filament which possibly reduce the settlement of heavier mix constituents
(e.g., aggregates), thereby reducing the upward movement of water (bleeding) in
concrete and also the rate of moisture loss from the exposed surface on concrete.
[Alhozaimy et al (1995)].
4.4.
MECHANICAL PROPERTTIES OF HARDENED PPFRC
The addition of the PPF to the concrete mixtures has beneficial effects on the
mechanical properties of hardened concrete. The effect of volume of fibres (Vf) and
the length of fibres (Lf) on the mechanical properties such as compressive strength,
split cylinder tensile strength, flexural tensile strength at different test ages are
reported.
60
4.4.1. Compression Test Results
The compressive strength tests were performed on one plain concrete mixture
“Control” concrete and six (6) polypropylene fibre reinforced concrete (PPFRC)
mixtures. The seven different mixtures were PPC, PPFRC 0.4-25, PPFRC 0.6-25,
PPFRC 0.8-25, PPFRC 0.4-38, PPFRC 0.6-38, and PPFRC 0.8-38 respectively.
These were tested at the ages of 7, 14 and 28 days. Three replicate specimens were
tested at each test age for each type of mixture.
At each of the test age, three (3) specimen were taken out from curing, dried and then
caped with sulphur and were tested to get the load-stroke data. From the load-stroke
data, stress-strain data was computed. From the stress-strain data of each of the 3
specimens, an average stress-strain data was obtained, which was plotted.
Microsoft Excel design sheet is attached in Appendix-I.
The
The resulting average
compressive stress-vertical displacement curves are shown in the figures.
The
pictorial views of the failure surface of PC and PPFRC specimen are shown in Figure
4.16 and Figure 4.17 respectively.
The effect of volume fraction of fibre (Vf) on the compressive stress- strain at
different test ages is shown in Figure 4.18 – Figure 4.23. From figures it is clear that
the fibres tend to increase the ductility of the mix by increasing the failure strains
however these have varying effect on the compressive strength. The smaller strain of
PC is because of the fact that after the concrete reaches its peak stress; cracks appear
and as the loading continues the failure is occurred by the crushing of the concrete
specimen at a relatively lower value of strain. However in PPFRC mixtures the
increase in strains is due to the fact that these fibres have an interlocking capability
which allows these to hold the mixture together even after cracking and so prevents
the effect of shattering force. In PPFRC specimens, the bulging of specimens was
observed without any significant deterioration of the test specimen.
The effect of length of fibre (Lf) on the compressive stress- strain of concrete mixture
tested at different test ages is shown in and Figure 4.24 – Figure 4.32. The figures
show that the 28 day strengths of PPFRC with 25 mm long fibres are greater than that
61
on the respective PPFRC with 38 mm long fibres. This is true for all the volume
fractions used.
The strength-time curve for PC and the six (6) PPFRC mixtures are shown in Figure
4.33 – Figure 4.37. The compressive strengths of PPFRC mixtures are found to be
less than that of PC except for the PPFRC 0.6-25 which showed an increase of 19.4%
in 28 day strength.
The decrease in compressive strength may be because the
presence of fibres introduces more air voids in the composite and also create
consolidation and compaction problems and hence reduces the compressive strength
of the mix.
4.4.2. Splitting Cylinder Tensile Test Results
The splitting cylinder tensile tests were performed on one plain concrete mixture
“Control” concrete and six (6) polypropylene fibre reinforced concrete (PPFRC)
mixtures as described in the Section 4.4.1 of the report. The seven different mixtures
were PPC, PPFRC 0.4-25, PPFRC 0.6-25, PPFRC 0.8-25, PPFRC 0.4-38, PPFRC
0.6-38, and PPFRC 0.8-38 respectively. These were tested at the ages of 7, 14 and 28
days. Three replicate specimens were tested at each test age for each type of mixture.
At each of the test age, the specimens were tested and the load-stroke data was
obtained from which stress-displacement data was computed.
From the stress-
displacement data of each of the 3 specimens, an average stress-displacement data
was obtained, which was plotted. The Microsoft Excel design sheet is attached in
Appendix-I. The resulting average splitting tensile stress-vertical displacement curves
are shown in the Figures.
The average stress-displacement behaviour of PC shows a linear trend up to the
cracking (Figure 4.38). After the first crack occurs, the strength of the PC reduces
immediately and the crack widening leads to the splitting of the cylinder. (See Figure
4.39)
The average stress-displacement behaviour of PC and PPFRC with different Vf and Lf
at different test ages are shown in Figure 4.40- Figure 4.54. From these figures, it can
62
be seen that the stress-displacement behaviour up to first crack is almost the similar
for both PC and PPFRC; however the post-peak behaviour is different and the
addition of PP fibres to concrete helps in increasing the post peak deformation
capacity and enhancing the post-cracking strength of PPFRC in tension.
In the case of PPFRC, the PP fibres come into action after the first crack. The PP
fibres bridge these cracks and restrain them from further opening and hence improve
the load-carrying capacity of structural member beyond cracking. After the first crack,
a drop in the stress is noted which shows the stress transfer from concrete to the
randomly distributer fibres, which further take the applied load by elongating. (See
Figure 4.55) The failure or the splitting on the cylinder occurred when the fibres
elongation exceed the allowable i.e. the breaking of the fibres under axial tension.
(See Figure 4.56)
The effect of Vf on average strength-time curves for these concrete mixtures is shown
in Figure 4.57 and Figure 4.58 and the effect of Lf on the average splitting tensile
strength-time curves is shown in Figure 4.59-Figure 4.61.
4.4.3. Flexural (Indirect Tensile) Test Results
The flexural tests were performed on beam specimen prepared from the same seven (7)
of mixtures as mentioned in Section 4.1 and the tests were performed at test age of 28
days only.
At the test age, three (3) replicate specimens were tested with the Universal Testing
Machine (UTM) following the procedure described in the Chapter 3 of the report.
The loading assembly and test set –up is shown in Figure 4.62.
The behaviour of the PC and six (6) different PPFRC beams under flexure test were
similar to that under splitting tensile strength test as both the tests indicate the indirect
tensile behaviour (strength) of the material. Before the occurrence of the first crack,
the load-deflection behaviour of all PPFRC beams was found to be similar to that of
the plain concrete “control” beams. Just after the appearance of the first crack,
“control” beams suddenly failed and the load-defection behaviour showed a steep and
63
sharp drop after the peak (maximum) load and thus exhibited little or no post-cracking
deformation capacity (Figure 4.63).
However in PPFRC beams, after the occurrence of the first crack, a drop is observed
in the load-deflection curve as the load is released and transferred from the matrix to
the fibres, and afterwards that the beams continues to withstand a portion of the load
with increasing deformations and widening of the cracks (Figure 4.64) The PPFRC
beams continue to resist load with increasing deformations by virtue of the elongation
of the randomly distributed discrete fibres and ultimately fails at large deformations as
the fibres reach their maximum elongation (Figure 4.65) The fractured surfaces of the
PC and the PPFRC beams are shown in Figure 4.66.
The load-stroke data was obtained from which strength-displacement data was
computed and plotted. The Microsoft Excel design sheet is attached in Appendix-I.
The effect of Vf on the average flexure strength-displacement curves of the concrete
mixtures is shown in Figure 4.67 and Figure 4.68. The peak flexure strength of PC
beams is higher than that of PPFRC beams however PPFRC beams showed greater
displacement capacity. Among the PPFRC beams with different Vf of PPF, the beams
with Vf 0.8% (7.2 Kg/m3) of both the 25 mm and 38 mm long PPF showed greatest
deformation (vertical displacement). The effect of Lf on the average flexure strengthdisplacement curves is shown in Figure 4.69 to Figure 4.71. The PPFRC with 38 mm
long PPF showed greater deformation (vertical displacement) capacity as compared to
the PPFRC with 25 mm long PPF. The combined effect of Vf and Lf on the average
flexure strength-displacement behaviour is that the PPFRC with the greatest Vf and Lf
showed the greatest vertical displacement. Numerically the PPFRC 0.8-38 beams
showed the average vertical displacement of about 20 times greater than that of
control beams. The displacement ductility is improved by the introduction of PPF
(see Table 4.2).
64
Table 4.1
Test results of various fresh properties tests of PC and PPFRC with
different volume fraction and length of fibre
Standard Slump
Test
Mix No.
Vertical
Slump
Slump
Type
(in)
PC
PPFRC
0.4-25
PPFRC
0.6-25
PPFRC
0.8-25
PPFRC
0.4-38
PPFRC
0.6-38
PPFRC
0.8-38
Compacting
Factor Test
Flow
Table
Test
J-Ring
Test
L- Box
Test
V-Funnel
Test
C.F
(computed)
Dia.
Dia.
Blocking
Ratio
H₂/H₁
Flow
Time
(kg/kg)
(in)
(in)
(in/in)
(sec.)
8.0
True
0.987
15.35
14.0
0.58
3.79
6.5
True
0.957
15.0
12.5
Blockage
Blockage
6.0
True
True
0.944
13.5
12.0
Blockage
Blockage
0.919
12.0
11.0
Blockage
Blockage
3.8
9.0
Collapse
0.986
15.5
15.3
Blockage
Blockage
7.5
Collapse
0.956
14.0
13.0
Blockage
Blockage
6.8
Collapse
0.94
14.35
13.35
Blockage
Blockage
65
Table 4.2
Time
Shrinkage test results of PC and PPFRC
Mix ID
(hour)
0
24
48
72
0
24
48
72
0
24
48
72
0
24
48
72
0
24
48
72
PC
PPFRC 0.2-25
PPFRC 0.4-25
PPFRC 0.2-38
PPFRC 0.4-38
ΔL
ΔL
ΔL
Average ΔL
(%)
(%)
(%)
(%)
0.000
-0.5562
-0.6985
0.000
-0.407
-0.420
0.000
-0.630
-0.643
0.000
-0.531
-0.587
-0.6985
0.0000
-0.2119
-0.3841
-0.512
0.000
-0.473
-0.578
-0.746
0.000
-0.080
-0.133
-0.652
0.000
-0.255
-0.365
-0.4106
0.0000
-0.0137
-0.0684
-0.591
0.000
-0.013
-0.026
-0.133
0.000
-0.013
-0.025
-0.378
0.000
-0.013
-0.040
-0.1643
-
-0.078
0.000
-0.039
-0.064
-0.076
0.000
-0.101
-0.127
-0.106
0.000
-0.070
-0.096
-
-0.103
0.000
-0.107
-0.413
-0.228
0.000
-0.099
-0.149
-0.165
0.000
-0.103
-0.281
-
-0.426
-0.199
-0.313
66
Table 4.3
Weight measurements of PC and PPFRC
Time
Weight (gms.)
(hours)
PC
PPFRC 0.2-25
PPFRC 0.4-25
PPFRC 0.2-38
PPFRC 0.4-38
0
6740
6838
6.762
6.806
6.816
24
6660
6744
6.672
6.620
6.607
48
6631
6712
6.645
6.616
6.603
72
6618
6695
6.636
6.609
6.600
Table 4.4
Weight loss percentage of PC and PPFRC
Time
Weight loss (%)
(hours)
PC
PPFRC 0.2-25
PPFRC 0.4-25
PPFRC 0.2-38
PPFRC 0.4-38
0
0
0
0
0
0
24
-1.187
-1.375
-1.331
-2.733
-3.066
48
-1.617
-1.843
-1.730
-2.792
-3.125
72
-1.810
-2.091
-1.863
-2.895
-3.169
Table 4.5
Displacement ductility calculated from experimental results for
the flexure tests of PC and PPFRC with different volume fraction and
length of fibre
Concrete Mix
PC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
PPFRC 0.4-38
PPFRC 0.6-38
PPFRC 0.8-38
Displacement at
Yield
δy
(in)
0.039094
0.039685
0.037205
0.042756
0.044488
0.036220
0.044961
Displacement at
Ultimate
δu
(in)
0.042598
0.490866
0.440000
0.538228
0.680394
0.841417
0.924094
67
Displacement
Ductility
µ
(in/in)
1.089627
12.369048
11.826455
12.588398
15.293805
23.230435
20.553246
Figure 4.1
Pictorial view of the slump cone after the removal of the standard
slump cone for PPFRC trial mix.
Figure 4.2
Pictorial view of measurement of the weight of partially compacted
fresh concrete for evaluating Compacting factor
68
Figure 4.3
Pictorial view of measurement of the diameter of fresh concrete after
flow table test for PC
Figure 4.4
Pictorial view of J-Ring test for PC
69
Figure 4.5
Pictorial view of J-Ring test for PPFRC 0.8-25
Figure 4.6
Pictoria view of L-Box test for PC
70
Figure 4.7
Pictorial view of L-Box test for PPFRC 0.8-38.
Figure 4.8
Pictorial view of V-Funnel test for PC
71
Figure 4.9
Effect of Fibre length (Lf ) on slump
Figure 4.10
Effect of fibre volume fraction (Vf ) on slump
72
Figure 4.11
Relationship between slump and compacting factor
Figure 4.12
Relationship between slump and flow table diameter
73
Figure 4.13
Pictorial view of length measurement for PPFRC specimen
Figure 4.14
Average shrinkage-time curve for PC and PPFRC
74
Figure 4.15
Average weight loss-time curve for PC and PPFRC
75
Figure 4.16 Pictorial views of PPC and PPFRC specimens under compressive
strength test.
Figure 4.17 Pictorial views of PCC and PPFRC specimens after compressive
strength test.
76
3000
PCC
PPFRC 0.4-25
PPFRC 0.6-25
2500
PPFRC 0.6-25
PCC
PPFRC 0.8-25
Avg. Stress (psi)
2000
PPFRC 0.4-25
1500
1000
PPFRC 0.8-25
500
0
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
Avg. Strain (in/in)
Figure 4.18 Effect of Vf on average compressive stress-strain curve for PCC and
PPFRC with 25 mm long fibres at 7 days.
3000
PCC
PPFRC 0.4-38
PPFRC 0.4-38
2500
PPFRC 0.6-38
Avg. Stress (psi)
PCC
2000
PPFRC 0.8-38
PPFRC 0.6-38
1500
PPFRC 0.8-38
1000
500
0
0
0.001
0.002
0.003
0.004
0.005
Avg. Strain (in/in)
0.006
0.007
PPFRC with 38 mm long fibres at 7 days
77
0.008
3000
PCC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
PPFRC 0.6-25
2500
PPFRC 0.4-25
Avg. Stress (psi)
2000
PPFRC 0.8-25
PCC
1500
1000
500
0
0
0.001
0.002
0.003
0.004
0.005
Avg. Strain (in/in)
0.006
0.007
0.008
0.009
3000
PCC
PPFRC 0.4-38
2500
PPFRC 0.6-38
PPFRC 0.6-38
Avg. Stress (psi)
PPFRC 0.8-38
PCC
2000
PPFRC 0.4-38
1500
1000
500
PPFRC 0.8-38
0
0
0.001
0.002
0.003
0.004
0.005
Avg. Strain (in/in)
0.006
0.007
0.008
78
0.009
4500
Avg. Stress (pssi)
PCC
4000
PPFRC 0.6-25
3500
PCC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
PPFRC 0.4-25
3000
2500
PPFRC 0.8-25
2000
1500
1000
500
0
0
0.002
0.004
0.006
Avg. Strain (in/in)
0.008
0.01
0.012
4500
PCC
4000
PPFRC 0.4-38
PCC
Avg. Stress (psi)
3500
PPFRC 0.6-38
PPFRC 0.8-38
PPFRC 0.6-38
3000
2500
PPFRC 0.4-38
2000
PPFRC 0.8-38
1500
1000
500
0
0
0.002
0.004
0.006
Avg. Strain (in/in)
0.008
0.01
79
0.012
3000
PCC
PPFRC 0.4-25
2500
PPFRC 0.4-38
PPFRC 0.4-38
Avg. Stress (psi)
2000
PCC
1500
1000
500
PPFRC 0.4-25
0
0
0.001
0.002
0.003
0.004
0.005
Avg. Strain (in/in)
0.006
0.007
0.008
Figure 4.24 Effect of Lf on average compressive stress-strain curve for PCC and
PPFRC with 0.4% volume fraction of PPF at 7 days.
3000
PCC
PPFRC 0.6-25
PPFRC 0.6-38
PPFRC 0.6-25
2500
Avg. Stress (psi)
2000
PCC
PPFRC 0.6-38
1500
1000
500
0
0
0.001
0.002
0.003
0.004
0.005
Avg. Strain (in/in)
0.006
0.007
80
0.008
3000
PCC
PPFRC 0.8-25
2500
PPFRC 0.8-38
Avg. Stress (psi)
2000
PCC
PPFRC 0.8-25
1500
PPFRC 0.8-38
1000
500
-0.001
0
1E-17
0.001
0.002
0.003
0.004
Avg. Strain (in/in)
0.005
0.006
0.007
0.008
3000
PCC
Avg. Stress (psi)
2500
PPFRC 0.4-25
PPFRC 0.4-25
PCC
PPFRC 0.4-38
PPFRC 0.4-38
2000
1500
1000
500
0
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
Avg. Strain (in/in)
81
0.009
3000
PCC
2500
PPFRC 0.6-25
PPFRC 0.6-25
Avg. Stress (psi)
PPFRC 0.6-38
2000
PCC
1500
1000
PPFRC 0.6-38
500
0
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
Avg. Strain (in/in)
3000
PCC
PPFRC 0.8-25
2500
PPFRC 0.8-38
PCC
Avg. Stress (psi)
2000
PPFRC 0.8-25
1500
PPFRC 0.8-38
1000
500
0
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
Avg. Strain (in/in)
82
0.009
4500
PCC
4000
PPFRC 0.4-25
PCC
3500
PPFRC 0.4-38
PPFRC 0.4-25
Avg. Stress (pssi)
3000
2500
PPFRC 0.4-38
2000
1500
1000
500
0
0
0.002
0.004
0.006
0.008
0.01
0.012
Avg. Strain (in/in)
4500
PCC
PPFRC 0.6-25
4000
3500
PPFRC 0.6-25
PCC
PPFRC 0.6-38
Avg. Stress (pssi)
3000
PPFRC 0.6-38
2500
2000
1500
1000
500
0
0
0.002
0.004
0.006
0.008
0.01
Avg. Strain (in/in)
83
0.012
4500
PCC
4000
PPFRC 0.8-25
3500
PCC
PPFRC 0.8-38
Avg. Stress (pssi)
3000
2500
PPFRC 0.8-25
2000
PPFRC 0.8-38
1500
1000
500
0
0
0.002
0.004
0.006
0.008
0.01
0.012
Avg. Strain (in/in)
4500
Avg. Compressive Strength (psi)
4000
3500
3000
2500
2000
1500
PCC
1000
PPFRC 0.4-25
500
PPFRC 0.6-25
PPFRC 0.8-25
0
0
7
14
21
28
Days
Figure 4.33 Effect of Vf on average compressive strength-time curve for PCC and
84
35
4000
3500
3000
2500
2000
1500
PCC
1000
PPFRC 0.4-38
PPFRC 0.6-38
500
PPFRC 0.8-38
0
0
7
14
21
28
35
Days
Figure 4.34 Effect of Vf on average compressive strength-time curve for PCC and
3500
3000
2500
2000
1500
PPFRC 0.4-25
PPFRC 0.4-38
1000
0
7
14
21
28
Days
Figure 4.35 Effect of Lf on average compressive strength-time curve for PPFRC
with 0.4% volume fraction of PP fibres.
85
35
4500
4000
3500
3000
2500
2000
PPFRC 0.6-25
1500
PPFRC 0.6-38
1000
0
7
14
21
28
35
Days
4500
PPFRC 0.8-25
4000
PPFRC 0.8-38
3500
3000
2500
2000
1500
1000
0
7
14
21
28
Days
86
35
400.00
350.00
PCC
Avg. Splitting Stress (psi)
PC
300.00
250.00
200.00
150.00
100.00
50.00
0.00
0
0.05
0.1
0.15
0.2
0.25
0.3
Vertical Displacement (in)
Figure 4.38
Average splitting tensile stress-displacement curve for PC at 7 days.
Figure 4.39 Pictorial view of failure surface of PC specimen under split tensile
strength test.
87
400.00
350.00
PCC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
PC
300.00
PPFRC 0.8-25
250.00
PPFRC 0.6-25
PPFRC 0.4-25
200.00
150.00
100.00
50.00
0.00
0
0.05
0.1
0.15
0.2
0.25
0.3
Figure 4.40 Effect of Vf on average splitting tensile stress-displacement curve for
PC and PPFRC with 25 mm long fibres at 7 days.
400.00
350.00
PCC
PPFRC 0.4-38
PPFRC 0.6-38
PPFRC 0.8-38
PC
PPFRC 0.4-38
300.00
PPFRC 0.6-38
250.00
PPFRC 0.8-38
200.00
150.00
100.00
50.00
0.00
0
0.05
0.1
0.15
0.2
0.25
0.3
88
500
PCC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
450
PPFRC 0.6-25
Splitting Stress (psi)
400
350
PPFRC 0.4-25
300
250
200
PPFRC 0.8-25
150
PC
100
50
0
0
0.05
0.1
0.15
0.2
0.25
400
PCC
PPFRC 0.6-38
PPFCR 0.4-38
350
PPFRC 0.4-38
PPFRC 0.6-38
300
PPFRC 0.8-38
250
PPFRC 0.8-38
200
PC
150
100
50
0
0
0.05
0.1
0.15
0.2
0.25
89
500
PCC
PC
450
PPFRC 0.4-25
PPFRC 0.4 -25
400
PPFRC 0.6-25
PPFRC 0.6-25
350
300
PPFRC 0.8-25
PPFRC 0.8-25
250
200
150
100
50
0
0
0.05
0.1
0.15
0.2
0.25
PC and PPFRC with 25 mm fibres at 28 days.
500
PPFRC 0.4 -38
PC
450
400
350
PPFRC 0.6 -38
300
250
PPFRC 0.8 -38
200
PCC
150
PPFRC 0.4-38
100
PPFRC 0.6-38
50
PPFRC 0.8-38
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
PC and PPFRC with 38 mm fibres at 28 days.
90
0.4
400.00
PCC
PPFRC 0.4-25
PPFRC 0.4-38
350.00
PC
300.00
PPFRC 0.4-25
250.00
PPFRC 0.4-38
200.00
150.00
100.00
50.00
0.00
0
0.05
0.1
0.15
0.2
0.25
Figure 4.46 Effect of Lf on average splitting tensile stress-displacement curve for
PC and PPFRC with 0.4% volume fraction of PPF at 7 days.
400.00
PCC
PC
350.00
PPFRC 0.6-25
PPFRC 0.6-38
300.00
PPFRC 0.6-25
250.00
PPFRC 0.6-38
200.00
150.00
100.00
50.00
0.00
0
0.05
0.1
0.15
0.2
91
0.25
400.00
PCC
PPFRC 0.8-25
PPFRC 0.8-38
350.00
PC
300.00
Splitting Stress (ksi)
PPFRC 0.8-25
250.00
PPFRC 0.8-38
200.00
150.00
100.00
50.00
0.00
0
0.05
0.1
0.15
0.2
0.25
500
PCC
450
PPFRC 0.4-25
400
PPFRC 0.4-38
350
PPFRC 0.4-25
300
PPFRC 0.4-38
250
PC
200
150
100
50
0
0
0.05
0.1
0.15
0.2
92
0.25
400
PCC
PPFRC 0.6-25
350
PPFRC 0.6-38
300
PPFRC 0.6-38
PPFRC 0.6-25
250
PC
200
150
100
50
0
0
0.05
0.1
0.15
0.2
0.25
350
PC
300
PCC
PPFRC 0.8-25
PPFRC 0.8-38
PPFRC 0.8-25
250
PPFRC 0.8-38
200
150
100
50
0
0
0.05
0.1
0.15
0.2
93
0.25
500
PC
450
PPFRC 0.4-38
400
350
300
PPFRC 0.4 -25
250
200
150
PCC
100
PPFRC 0.4-25
50
PPFRC 0.4-38
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
500
PCC
PPFRC 0.6-25
PPFRC 0.6-38
PC
450
400
PPFRC 0.6-38
350
300
PPFRC 0.6-25
250
200
150
100
50
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
94
0.4
500
PCC
450
PPFRC 0.8-25
PC
PPFRC 0.8-38
400
350
PPFRC 0.8-25
300
PPFRC 0.8-38
250
200
150
100
50
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Figure 4.55
tensile test.
Pictorial view of crack propagation of PPFRC cylinder under splitting
95
0.4
Figure 4.56
Pictorial view of the split PPFRC cylinder
Avg. Splitting Tensile Strength (psi)
500
450
400
350
300
250
PCC
200
PPFRC 0.4-25
150
PPFRC 0.6-25
PPFRC 0.8-25
100
0
7
14
21
28
Days
Figure 4.57
96
35
Avg. Splitting Tensiole Strength (psi)
500
450
400
350
300
250
PCC
200
PPFRC 0.4-38
150
PPFRC 0.6-38
PPFRC 0.8-38
100
0
7
14
21
28
35
Days
Figure 4.58 Effect of Vf on average splitting tensile strength-time curve for PC and
500
450
400
350
300
PPFRC 0.4-25
250
PPFRC 0.4-38
200
0
7
14
21
28
Days
Figure 4.59 Effect of Lf on average splitting tensile strength-time curve for PPFRC
97
35
500
450
400
350
300
PPFRC 0.6-25
250
PPFRC 0.6-38
200
0
7
14
21
28
35
Days
500
450
400
350
300
250
PPFRC 0.8-25
PPFRC 0.8-38
200
0
7
14
21
28
Days
98
35
Figure 4.62
test.
Pictorial view of the loading assembly for the two-point load flexure
Figure 4.63
Pictorial view of the PC beam after failure.
99
Figure 4.64 Pictorial view of the PPFRC beam during flexure testing, showing
wide crack and vertical displacement.
Figure 4.65
Pictorial view of the PPFRC beam after collapse.
100
Figure 4.66
failure.
Pictorial view of the PC and PPFRC beam fractured surface after
10
PCC
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
9
PC
8
7
fr (ksi)
6
5
4
PPFRC 0.4-25
PPFRC 0.6-25
PPFRC 0.8-25
3
2
1
0
0
0.2
0.4
0.6
Displacement (in)
0.8
1
Figure 4.67 Effect of Vf on average flexure stress-displacement curve for PC and
101
1.2
10
PCC
PPFRC 0.4-38
PPFRC 0.6-38
PPFRC 0.8-38
9
PC
8
7
fr (ksi)
6
5
PPFRC 0.4 -38
4
3
PPFRC 0.6 -38
2
PPFRC 0.8 -38
1
0
0
0.2
0.4
0.6
Displacement (in)
0.8
1
1.2
Figure 4.68 Effect of Vf on average flexure stress-displacement curve for PC and
10
PCC
9
PPFRC 0.4-25
PC
8
PPFRC 0.4-38
7
fr (ksi)
6
5
4
PPFRC 0.4-25
3
PPFRC 0.4-38
2
1
0
0
0.2
0.4
0.6
Displacement (in)
0.8
1
Figure 4.69 Effect of Lf on average flexure stress-displacement curve for PC and
102
1.2
10
PCC
PPFRC 0.6-25
PPFRC 0.6-38
9
PC
8
7
fr (ksi)
6
5
4
PPFRC 0.6-25
3
PPFRC 0.6-38
2
1
0
0
0.2
0.4
0.6
Displacement (in)
0.8
1
1.2
10
9
PCC
PPFRC 0.8-25
PPFRC 0.8-38
PC
8
7
fr (ksi)
6
5
4
PPFRC 0.8-25
3
2
PPFRC 0.8-38
1
0
0
0.2
0.4
0.6
Displacement (in)
0.8
1
103
1.2
CHAPTER 5
ANALYTICAL WORK
5.1.
INTRODUCTION
The chapter presents the analytical solution for stress-strain curves for PPFRC under
compression using fractional equation. This model is developed in order to calibrate
the compressive stress-strain curves obtained after testing the cylindrical specimen at
the Material Testing Laboratory of the NED University of Engineering and
Technology. The fractional equations used for this work are described in the next
section followed by the analytical solution for the PC and PPFRC mixtures used in
this study.
5.2.
FRACTIONAL EQUATION FOR COMPRESSIVE STRESS
STRAIN CURVE FOR PPFRC
A fractional equation developed by Ahmad and Shah (1979, 1982, 1985) is used for
analytically predicting the compressive stress-strain curve of plain and polypropylene
fiber reinforced concrete (PPFRC).
The fractional equation is expressed as
Y=
( )
(Eq. 5.1)
( –) Where
Y = fc/fc
'
'
X = Ɛ c/ Ɛc
For Plain Concrete
Ɛ'c = 0.001648+0.000114 (f’c)
(Eq. 5.2)
104
'
The Equation for peak strain (Ɛ c ) and constants for plain concrete were calibrated
from a large data base by Ahmad and Shah (1-5). For pre-peak portion of the curve
'
'
(Ɛc < Ɛ c ), the constants are A1, D1 are for the post-peak curve (Ɛc > Ɛ c ), the
constants are A2, D2.. The calibrated constants for plain concrete of various strengths
are shown in Table 5-1. For a given strength of plain concrete, the complete stressstrain curve can be obtained by using appropriate constants in the fractional equation
and different values of strain as input and obtaining the corresponding values of
stress.
For the PPFRC, the fractional equation for plain concrete is used and the constants A
and D were calibrated from the experimental test results for various length (Lf) of the
PPF and various volume fractions (Vf) of PPF. The calibrated constants for PPFRC
with different various lengths (Lf) of the PPF and different volume fractions of PPF
(Vf) are shown in Table 5.2.
5.3.
COMPARISION BETWEEN EXPERIMENTAL RESULTS
AND ANALYTICAL EXPRESSION
The comparison of the experimental compressive stress strain curves and the
analytical curves predicted by the use of fractional equation and the calibrated
constants are shown in Figures 5.2 – 5.8. The comparisons are for the test age of 28
days.
Figures 5.2-5.8 show that the analytical equation with calibrated constants adequately
predicts the compressive stress strain curve of PPFRC and captures the effects of
different various lengths (Lf) of the PPF and different volume fractions of PPF (Vf) on
the stress strain curve.
5.4.
SIMPLIFICATION OF CONSTANTS IN FRACTIONAL
EQUATION
For simplification of the constants in the fractional equation, a regression analysis was
done for the values of the calibrated constants. The constants A1 and D1 and A2 and
D2 can be expressed in terms of fc’, Vf and Lf.
105
The resulting expressions are:
A1 = 1.37+0.01Lf-1.25Vf
R2 = 0.704
(Eq. 5.3)
D1 = 0.10-0.02Lf+3.13Vf
R2 = 0.517
(Eq. 5.4)
A2 = 0.12+0.001Lf+0.59Vf
R2 = 0.458
(Eq. 5.5)
D2= 1.13-0.00038Lf-0.28Vf
R2 = 0.4189
(Eq. 5.6)
And,
For generating the analytical compressive stress-strain curve of plain and PPFRC
concrete, the constants of Eq. 5.3-5.6 will facilitate the computations for the
compressive stress strain curve. The values of the constants were computed using
these equation and the values are presented in table 5.2.
106
Table 5-1
Calibrated constants of the fractional equation for PC (Plain) concrete
for different strengths of concrete [Ahmad and Shah (1979, 1982, 1985) ].
fc'
A1
D1
A2
D2
4
8
12
1.6003
1.3768
1.3244
0.6551
0.2581
0.1913
1.5045
0.283
0.1156
0.8801
0.9869
0.9964
Table 5-2
Calibrated constants of the fractional equation for PPFRC with
different Lf and Vf .
Lf
Vf
(mm)
(%)
A1
0.000
0.000
1.500
25.000
0.400
1.000
25.000
0.600
0.800
25.000
0.800
0.500
38.000
0.400
1.200
38.000
0.600
1.080
38.000
0.800
1.100
Average of Error Square
Lf
(mm)
Vf
A2
(%)
0.000
0.000
0.000
25.000
0.400
0.050
25.000
0.600
0.200
25.000
0.800
0.200
38.000
0.400
0.100
38.000
0.600
0.200
38.000
0.800
0.800
Average of Error Square
A1
Error
Square
(computed)
1.370
1.120
0.870
0.620
1.250
1.000
0.750
A2
(computed)
0.017
0.014
0.005
0.014
0.003
0.006
0.123
0.03
Error
Square
0.120
0.381
0.499
0.617
0.394
0.512
0.630
0.014
0.110
0.089
0.174
0.086
0.097
0.029
0.09
107
D1
0.500
0.700
0.500
2.000
0.600
0.700
3.000
D2
1.060
1.050
1.050
0.930
1.000
1.000
0.700
D1
(computed)
0.100
0.852
1.478
2.104
0.592
1.218
1.844
D2
(computed)
1.130
1.009
0.953
0.897
1.004
0.948
0.892
Error
Square
0.160
0.023
0.956
0.011
0.000
0.268
1.336
0.39
Error
Square
0.005
0.002
0.010
0.001
0.000
0.003
0.037
0.01
14
Stress (f'c = 4ksi)
Stress (f'c = 8ksi)
12
12 ksi
Stress (f'c = 12ksi)
Compressive Stress (ksi)
10
8 ksi
8
6
4 ksi
4
2
0
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
strain (in/in)
Figure 5.1
Typical analytical stress-strain curves of plain conrete of various
strengths (Ahmad and Shah, 1982)
108
0.009
Avg. Compressive Stress (psi)
4000
PCC (NED Analytical)
PC
(Experimental)
3500
PCC (Experimental)
3000
PC (NED
Analytical)
2500
2000
1500
1000
500
0
0
0.001
0.002
0.003
0.004
0.005
0.006
Avg. Strains (in/in)
Figure 5.2
Comparison of experimental and analytical compressive stress-strain
curve for PC at 28 days
3500
3000
PPFRC 04-25
(NED Analytical)
PPFRC 04-25
(Experimental)
PPFRC 0.4-25
(Experimental)
2500
PPFRC 0.4-25
(NED Analytical)
2000
1500
1000
500
0
0
0.001
0.002
0.003
0.004
Figure 5.3
curve for PPFRC 0.4-25 at 28 days
109
0.005
4500
PPFRC 06-25 (NED
Analytical)
PPFRC 06-25
(Experimental)
PPFRC 0.6-25
(Experimental)
4000
3500
3000
PPFRC 0.6-25
(NED Analytical)
2500
2000
1500
1000
500
0
0.000
0.002
0.004
0.006
0.008
0.010
0.012
Figure 5.4
3000
PPFRC 08-25 (NED
Analytical)
PPFRC 08-25
(Experimental)
2500
2000
PPFRC 0.8-25
(NED Analytical)
1500
1000
PPFRC 0.8-25
(Experimental)
500
0
0.000
0.001
0.002
0.003
0.004
Figure 5.5
110
3000
PPFRC 0.4-38
(Experimental
)
2500
2000
PPFRC 0.4-38
(Experimental)
PPFRC 0.4-38 (NED
ANALYTICAL)
PPFRC 0.4-38
(NED Analytical)
1500
1000
500
0
0.000
0.001
0.002
0.003
0.004
0.005
Figure 5.6
3500
3000
PPFRC 0.6-38 (NED
Analytical)
PPFRC 0.6-38
(Experimental)
PPFRC 0.6-38
(Experimental)
2500
2000
PPFRC 0.6-38
(NED Analytical)
1500
1000
500
0
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.010
0.011
Figure 5.7
111
2000
PPFRC 0.8-38
(NED Analytical)
1800
1600
PPFRC 08-38
(Experimental)
PPFRC 08-38 (NED
ANALYTICAL)
1400
PPFRC 0.8-38
(Experimental)
1200
1000
800
600
400
200
0
0.000
0.001
0.002
0.003
0.004
Figure 5.8
112
0.005
CHAPTER 6
APPLICATIONS OF PPFRC IN CIVIL
INFRASTRCUTURE
6.1.
INTRODUCTION
In this chapter, the applications of Polypropylene fibre reinforced concrete (PPFRC)
in civil infrastructure are described. The uniform dispersion of fibres throughout the
concrete mix provides near isotropic properties not common to conventionally
reinforced concrete.
The use of PPFRC in concrete construction and other
applications is driven by the enhanced properties of PPFRC exhibits as compared to
conventional concrete.
Polypropylene fibre reinforced concrete (PPFRC) is recommended in all types of
concretes which demonstrate a need for enhanced toughness characteristics, resistance
to intrinsic cracking and improved water tightness.
The main area of PPFRC
applications includes buildings, bridges, highway pavements, industrial floorings,
hydraulic structures, blast resistance, sewage and waste management and other
applications.
The major benefits of PPFRC include
•
Inhibits plastic settlement cracking.
•
Control plastic shrinkage cracking up to 80%.
•
Lowers water migration in concrete and control bleeding.
•
Improves flexural properties of concrete up to 30%.
•
Resist impact /shatter forces up to 14 times more than plain concrete.
•
Increase abrasion resistance significantly.
•
Provide fatigue endurance in fibre reinforced concrete not available in plain
concrete.
•
Improve fire resistances of concrete
113
The typical dosages of PPF in concrete for various applications are shown in Table
6.1. Some of the examples of applications of PPFRC in civil infrastructure in
Pakistan are presented next.
6.2.
APPLICATIONS IN BUILDINGS
The application of PPFRC in buildings include slabs, beams, balconies, overhangs
and ledges, driveways, sidewalks, screed toppings and overlays, rooftop screeding,
water storage tanks (both overhead and underground) pool construction, basements,
architectural finishes, cement tiles and plastering, coloured concrete, foundations,
drainage etc. Being wholly synthetic there is no corrosion risk. The possibility of
increased tensile strength and impact resistance offers potential reductions in the
weight and thickness of structural components and should also reduce the damage
resulting from shipping and handling. The application of PPFRC for plastering in
multi-storeyed building of Korangi is shown in Figure 6.1 and that of roof screeding
of a building in DHA is shown in Figure 6.2.
6.3.
APPLICATIONS IN BRIDGES
In order to enhance the seismic performance and serviceability of bridges, focus has
been on the development and implementation of innovative materials. PPFRC has the
potential for seismic applications due to its increased strain capacity and reduced
cracking i.e. its crack arresting capability. PPFRC is widely being used to control
early age cracking on bridge decks and overlays. The addition of micro-fibres in
amounts as small as 0.1% by volume is an effective method to control plastic
shrinkage cracking in bridges. For controlling shrinkage cracking in bridge decks,
PPFRC is commonly used in expansion joints. Its application in one of the bridges in
Karachi is shown in Figure 6.3.
6.4.
APPLICATIONS IN HIGHWAY PAVEMENTS
Polypropylene fibre reinforced concrete (PPFRC) has been used in concrete slabs and
pavements
to
reduce
the
amount
of
required
shrinkage-and-temperature
reinforcement. For the same wheel loads, the thickness of slabs with PPFRC could
also be reduced and PPFRC slab of about ½ the thickness of conventional PCC slab
would have about the same load carrying capacity. PPFRC paved aircraft parking are
114
now in service in severe and mild environments. Example of use of in Shaheen Air,
Jinnah Airport Karachi, is shown in Figure 6.4
6.5.
APPLICATIONS IN INDUSTRIAL FLOORING
In industrial flooring, one of the main reasons of using polypropylene fibres in
concrete slab is for crack control (inhibition of cracks or arresting of cracks). Better
resistance to impact and other suddenly applied loads is also one of enhancements
that provided by the use of PPF in concrete. Fibres help in distributing the impact
forces to the entire body of concrete, thus reducing the concentration of the impact
forces. Example of application of PPFRC in industrial flooring is shown in Figure
6.5.
6.6. APPLICATIONS IN DAMS AND HYDRAULIC
STRUCTURES
PPFRC is being used for the construction and repair of dams and other hydraulic
Structures to provide better resistance to cavitation and severe erosion. The addition
of polypropylene fibres in concrete has significant beneficial effects on reducing the
deterioration of concrete surface skin subjected to sea water attack. Application of
PPFRC in hydraulic structures is shown in the construction of water reservoir at
Diamond Terrace, Gulshan-e-Maymar, Karachi (Figure 6.6).
6.7.
APPLICATIONS IN BLAST RESISTANCE
Since PPFRC exhibits superior impact resistance properties, its use in structures
exposed to sudden impact or blast loading has advantages. The use of PPFRC in blast
resistant structures can also have an additional benefit as it exhibits better fire
resistance properties, in case fire accompanies the blast loading. Use of PPF in
concrete cement plaster and concrete works provide significant improvement,
reduction to spill-damage and better structural integrity. The effectiveness of PPFC in
withstanding the blast forces was studied in the Military College of Engineering,
Risalpur, Pakistan. (Figure 6.7)
115
6.8. APPLICATIONS IN SEWAGE AND WASTE WATER
MANAGEMENT
Polypropylene fibres are nonmagnetic and non-corrosive, as well as chemically inert.
These fibres can withstand the chemical environment inside concrete. Because these
fibres are unaffected by the alkaline environment of concrete, and are stable under
long-term heat exposure, these fibres do not degrade and provide durable concrete
reinforcement. These properties of fibres make them suitable for concrete application
in sewage, manholes and waste water treatment plants. (Figure 6.8-6.9)
6.9.
OTHER APPLICATIONS
The other applications of PPFRC include applications in plaster to reduce plastic
shrinkage cracking, applications to reduce plastic shrinkage cracking, and
applications to increase abrasion resistance, increase freeze and thaw durability,
control plastic settlement cracking etc. (Figure 6.10-6.11)
The lists of some projects where PPFRC is used for different applications are attached
in Appendix-II.
116
Table 6.1
Company)
Typical dosages of PPFRC for various applications (MATRIXX
Fibre
Length
(mm)
Type of Work
Minimum
Dosage
(gms/50 Kg
cement bag)
100
Plaster Works (Including Colour Crete)
6
External Plaster Works, Precast Concrete and Repair of
Plaster Works
Residential and Commercial Roof Screed and Roof
Slab, Industrial Flooring and Pavement, RCC Structure
for Water Tank, Basement Walls, Manhole and Canal
Lining
Water Reservoir, Sewerage Drain, Storm Water Drain
and Residential Roof Screed (Over Flexible Insulation
Base)
Heavy Duty Industrial Floor, Hanger Floor, Runway,
Quay Wall, Sea Block, Bridge Deck Screed, Expansion
Joint and
13
100
25+13
300
25+13
450
25
600
117
Figure 6.1
Application of PPFRC for plastering in Multistoried Building,
Mehrunnisa Welfare Trust, Korangi, Karachi, Pakistan.
Figure 6.2
Pakistan.
Application of PPFRC in Roof Screeding, Creek Vista, DHA, Karachi,
118
Figure 6.3
Application of PPFRC in Jam Sadiq Bridge Deck and Expansion Joint
at KPT Interchange, Karachi, Pakistan.
NIP, PQA
Figure 6.4
Application of PPFRC in steel free pavements at Shaheen Air, Jinnah
Airport, Karachi, Pakistan.
119
Figure 6.5
Application of PPFRC in Industrial Flooring of Razi & Sons,
Suppliers of Toyota Motors, Port Qasim, Karachi, Pakistan.
Figure 6.6
Application of PPFRC in the construction of water reservoir at
Diamond Terrace, Gulshan-e-Maymar, Karachi, Pakistan.
120
With Fibre
Without Fibre
Figure 6.7
Application of PPFRC for blast resistance, Military College of
Engineering, Risalpur, Pakistan.
Figure 6.8
Applications of PPFRC for Sewage Channel, Khayaban-e-Jami, DHA,
Karachi, Pakistan.
121
Depth: 8 to 30 ft
KWSB
Figure 6.9
Application of PPFRC for Man holes in industrial zone, Landhi, North
Karachi, Pakistan.
Without
Fibre
Without Duracrete
Fibres
WithFibres
Duracrete Fibre
With
Figure 6.10 Application of PPFRC to reduce shrinkage cracking in column footing,
Karachi, Pakistan.
122
Abrasion Resistance
Without Fibre
Duracrete Fibre
Without
WithFibre
Duracrete Fibre
With
Figure 6.11 Application of PPFRC to reduce abrasion resistance in concrete
pavement, Karachi, Pakistan.
123

ppfrc - Construction Materials Research Group (CMRG)

Transcription

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