permeability of concrete mix design - IJRREST, International Journal

IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN
ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-4, ISSUE-1, APRIL-2015
(Proceedings of “6th National Conference on Make in India PMs Vision : Role of Engineering and Management
Innovations to Achieve this Vision” Organised by Apex Group of Institutions, Karnal, Haryana, India, April -2015)
PERMEABILITY OF CONCRETE MIX DESIGN
Hawa S ingh
Apex Group of Institutions, Department of Civil Engineering, Karnal (Haryana), India,
Email: [email protected]
Abstract- In the present investigation, study of water permeability of concrete was carried out..The strength of concrete is
depend on its mix proportions. we used high strength concrete which have its compressive strength is above 50 MPa.in
order to measure co-efficient of permeability as per IS:3085-1965,the cylinder with height to diameter ratio equal to one
were cast and subjected to a constant pressure 8kg/cm2.The coefficient of permeability was then calculated using Darcy’s
law. In the mix ,we are used so many pozzolanic materials for water tightness purposes.it doesn’t affect the density and
tensile strength of the concrete. The permeability is a measure of rate of movement of fluids through concrete, and is
sometimes even regarded as a direct measure of durability. The understanding of the physical processes of flow of fluids
requires knowledge of permeability. The permeability of concrete affects both types of concrete affects both types of
structures situated either in moderate environment areas or in coastal areas, the effect more pronounced on the latter
ones.
Keywords : Concrete , Water Cement ratio , Silica fumes.
1. INTRODUCTION
Concrete is most widely used man made construction material, commonly obtained by mixing by Portland
cement, sand, aggregate and water. The Annual average of consumption of concrete is estimated to be about one
tonne for every human being .The reason behind this amount, because concrete can formed into a variety of
shapes and size and cheapest and most readily available material on the job .the next reason which is most
relevant to the present work is that the concrete possesses excellent resistance to water without serious
deterioration. The use of concrete in many kind of hydraulic structure, sub-structure, under water marine
structure and chemical industries now-a-days is well known. In hydraulic structure many time the water
tightness of concrete is of greater importance than strength. In concrete, water is present as a necessary for the
cement hydration reaction and as a plasticizing agent. With due course of time depending on the environmental
conditions and thickness of concrete element, all the capillary water and a part of absorbed water is lost, leaving
the pores unsaturated or empty. Since it is the evaporable water, a concrete will not be vulnerable to water –
related destructive phenomena, provided the subsequent exposure of concrete to the environment does not lead
to re-saturation of pores. To a large extent it depends on permeability of concrete.
2. PERMEAB ILITY OF CONCRETE
Permeability is defined as the ease with which a fluid can pass through concrete under a pressure difference and
is measured in term of co-efficient of permeability. When the flow is steady the co-efficient of permeability is
determined by the darcy’s law.
K=D/[ATH/L]
........................... (1)
Where K=co-efficient of permeability[m/s]
D/T= Rate of flow[m3/s]
H/L=Ratio of pressure head to thickness of specimens both expressed in same units.
A= Area of cross-section of the specimen[m2]
The co-efficient of permeability of concrete to gases or water vapour is much lower than the co -efficient for
liquid water, so, permeability is determined using water free from dissolved air. Permeability of concrete is of
particular significance in structure which are intended to retain water comes into contract with water.
Permeability is intimately related to durability of concrete and it influences the resistance of concrete to sulphate
and alkali attack, rate of corrosion of reinforcement, fire and frost.
2.1 Factor influence permeability of concrete.
In general, all the factor that increase the [a]void space in the concrete and [b] cracks and micro -cracks in
structure, increase the permeability. The different factors that influence the permeability of concrete can be
classified into three groups.
i] Concrete making constituents and admixture.
12 | P a g e | © IJRREST | h t t p : / / i j r r e s t . o r g / i s s u e s / ? p a g e _ i d = 1 2
IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN
ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-4, ISSUE-1, APRIL-2015
(Proceedings of “6th National Conference on Make in India PMs Vision : Role of Engineering and Management
Innovations to Achieve this Vision” Organised by Apex Group of Institutions, Karnal, Haryana, India, April -2015)
ii] Compaction and curing techniques.
iii] Age of concrete and environment exposure.
2.1.1 Concrete making constituents and admixture.
a] Effect of cement and water/cement ratio.
The properties of cement which effect the permeability of concrete are its fineness, porosity, degree of hydration
and quantity of cement used. For a given w/c raio, higher and finer the cement content lesser is the permeability.
Water is added to the concrete to achieve hydration of cement paste and to obtain workable concrete. Higher w/c
ratio makes concrete more workable but reduce the strength on the other hand. An increase in w/c beyond 0.6
causes the increase in permeability very rapidly. the mixing water is indirectly responsible for permeability of
the hydrated cement paste because its content determines first the total space and subsequently the unfilled
space after the water is consumed by either cement hydration reactions or evaporation to the environment. When
porosity decreases from 40 to 30%, the coefficient of permeability drops from 110 to 20 x 10 coefficient of
permeability drops from 110 to 20 x 10- -12 cm/sec. 12 cm/sec. and from a decrease in porosity from 30% to
20% and from a decrease in porosity from 30% to 20% results in a small drop in permeability.
b] Effect of aggregate
Compared to 30 to 40 percent capillary porosity of typical cement pastes in hardened concrete, the volume of
pores in most natural aggregates is us ually under 3 percent, and it rarely exceeds 10 percent. However, the
coefficient of permeability of aggregates is as variable as those of hydrated cement pastes of water/cement ratios
in the range 0.38 to 0.71. The reason some aggregates give much higher permeability than the cement paste is
that the size of capillary pores in aggregate is usually much larger.
Most of the capillary porosity in a mature cement paste lies in the range 10 to 100 nm, while pore size in
aggregates are, on the average, larger than 10 microns. For a given water/cement ratio, greater the maximum
size of aggregate, greater will be the flow. Well-graded aggregates, render a less permeability concrete.
2.1.2 Compaction and Curing Techniques
Compaction eliminates the entrapped air from the concrete and reduce the porosity of concrete. The
permeability and porosity, to some extent , are interrelated. Lesser the porosity, lower is the permeability.
Sometimes over-compaction leads to bleeding of concrete. In such case the voids left behind are oriented in the
same direction and the permeability of concrete in that direction increases.
Curing is necessary to promote the hydration of cement.as the time of curing increase, permeability of concrete
decrease. As wet cured concrete gives less permeable concrete than steam cured concrete.
2.1.3 Effect Of Age Of Concrete And Environmental Conditions:With the –passage of time , the hydration of cement approaches to a higher degree, thus improving the strength
of concrete. So, as the age of concrete increase, strength of concrete increase and permeability reduces.
Freeze and thaw develop cracks in concrete and make it more permeable, particular in wet condition. When
concrete is subjected to aggressive environment, e.g. in costal areas, the effect of sulphate becomes very
significant. Actually sulphate cause the concrete to expand. But interestingly, the pores and capillaries of
concrete when filled by sulphate render then solids and a reduction in porosity a nd permeability was observed.
3. AIMS OF PRESENT INVESTIGATION
The aim of the present investigation is to study the water permeability of concrete using IS code method. We
were used some many admixture for decreasing the permeability in concrete. We were used silica fumes to the
cement by weight basis. The quantity of admixture we were used in this mix is 5 to 15% by the weight of
cement.
4. EXPERIMENTAL INVESTIGATION
The investigation consist of casting and testing of two type of specimen’s viz. Cub es of viz. Cube of size150
mm and cylinder of 150 mm diameter and 150mm height for co -efficient of permeability respectively. Cement,
13 | P a g e | © IJRREST | h t t p : / / i j r r e s t . o r g / i s s u e s / ? p a g e _ i d = 1 2
IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN
ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-4, ISSUE-1, APRIL-2015
(Proceedings of “6th National Conference on Make in India PMs Vision : Role of Engineering and Management
Innovations to Achieve this Vision” Organised by Apex Group of Institutions, Karnal, Haryana, India, April -2015)
fine aggregates, and coarse aggregates in proporation of 1:0.6:2.1 were in preparing the concrete mix. To study
the pozzolanic materials, silica fume proportion in % of 5,10,15 used .
Figure.1 Permeability test set-up
5. TEST RESULT AND DISCUSSION
Addition of silica fume by 10 and 15% resulted in reduction in the permeability by 9 and 50% respectively.
This reduction of permeability can be attributed to the densification effect by silica fume and thus reducing
micro-cracks in concrete.
6. CONCLUS IONS
1.
Addition of 5, 10, 15% silica fume has reduced the permeability of concrete by 20% and 56% by using
sand stone and granite aggregate respectively.
2.
Similarly, silica fumes were found to be more effective in rendering the concrete more impermeable than
fly ashes. 5, 10 and 15% fly ash reduced the permeability by 50% 70% by using sand stone and granite
aggregate respectively.
7. REFERENCES
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14 | P a g e | © IJRREST | h t t p : / / i j r r e s t . o r g / i s s u e s / ? p a g e _ i d = 1 2
IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN
ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-4, ISSUE-1, APRIL-2015
(Proceedings of “6th National Conference on Make in India PMs Vision : Role of Engineering and Management
Innovations to Achieve this Vision” Organised by Apex Group of Institutions, Karnal, Haryana, India, April -2015)
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