Strength Prediction Models for Laterized Concrete Incorporating

Sciknow Publications Ltd.
AJCSE 2015, 2(2):11-15
DOI: 10.12966/ajcse.04.01.2015
American Journal of Civil and Structural Engineering
©Attribution 3.0 Unported (CC BY 3.0)
Strength Prediction Models for Laterized Concrete Incorporating
Used Engine Oil as Admixture
Olekwu Benjamin Elah 1,*, Gabriel Amode1, and Egbe-Ngu Ntui Ogork2
1
Department of Building, Federal University of Technology, Minna, Nigeria
Department of Civil Engineering, Bayero University, Kano
2
*Corresponding author (E-Mail: [email protected])
Abstract - This paper presents the findings of a research on the strengths of laterized concrete admixed with used engine oil
(UEO) and strength prediction models of the concrete. The compressive and splitting tensile strengths of UEO-laterized concrete
grade 30 (1:1.5:3 mix) were investigated at admixture levels of 0, 0.075, 0.15, 0.30 and 0.60% of UEO, respectively, at curing
ages of 7, 21, 28, 56, and 90 days in accordance with standard procedures. The strengths of UEO-laterized concrete were also
modelled using Minitab statistical software to establish regression models. Results of the investigation showed that the 28 days
compressive strength of laterized concrete without UEO was 28.78 N/mm 2 which is less than that required for grade 30 normal
concrete. It was found that the compressive strength and splitting tensile strength of laterized concrete decrease with increase in
UEO content. The highest reduction in the 28 days compressive strength of UEO-Laterized concrete was 15.88% of control at
UEO content of 0.60%. For structural application, 0.3% UEO should be used as the optimum percentage replacement in laterized
concrete to act as chemical retarder suitable for hot weather concreting and long haulage of ready mixed laterized concrete.
Regression models for UEO-laterized concrete for compressive strength and splitting tensile strength were developed with R 2
values of 0.899 and 0.925 respectively and considered to be good for prediction of laterized concrete strengths.
Keywords - Admixture, Laterized Concrete, Prediction Models, Strength, Used Engine Oil
1. Introduction
The current trends globally is research into the used of
by-products and waste products that can be recycled or used
as raw materials in the construction industry to reduce cost
and maintain ecological balance. Some of these by-products
or waste products can be used as aggregates, a portion of
aggregate, as components of concrete binder or ingredients in
manufactured aggregates. Some waste can also be used as
chemical admixtures and additive that can alter the fresh and
hardened properties of concrete.
Used engine oil (UEO) has been identified in the literature
as a waste material which less than 45% is being collected
worldwide while the remaining 55% is thrown into the
environment by the end user (Gamal, 2013). Also a study by
Bilal et al. (2003), on the effect of used engine oil on
properties of conventional concrete has been carried out on a
concrete mix contained 0.075, 0.15 and 0.30% used engine oil
by weight of cement. The result shows that used engine oil
acted as a chemical plasticizer improving the fluidity and
almost doubling the slump of the concrete mix. Furthermore,
used engine oil also increased the air content of the fresh
concrete mix (almost double), whereas the commercial
chemical air-entraining admixture almost quadrupled the air
content. They also found that used engine oil maintained the
concrete compressive strength whereas the chemical air-entra
ining admixture caused a loss of approximately 50% compre
ssive strength at all ages.
Oyinuola (2009) carried out a research on the influence of
diesel oil and bitumen on compressive strength of concrete
and found that both diesel oil and bitumen contaminated
cubes have their compressive strength increased up to 58 day
and 88 day respectively and reduced thereafter. He discovered
that the higher the percentages of diesel and bitumen in sand
the lower the concrete compressive strength obtained. He
explained that the strength reduction was because the surface
areas of sand particles were coated with oil, such that,
physical bond formation between cement paste and fine
aggregate was hindered.
In the construction industry, strength is a primary criterion
in selecting a concrete for a particular application (Ogork et
al., 2014). The strength of laterized concrete will depend on
the contents of used engine oil in the mix and the age of curing.
The gain in strength of concrete takes a long period of time
after casting. According to Ogork et al. (2014) reliable
prediction for strength of concrete is important, because it
provides the chance to carry out necessary adjustment on the
mix proportion used so as to avoid the situation where the
concrete does not reach the target design strength. Hence, a
12
American Journal of Civil and Structural Engineering (2015) 11-15
reliable strength prediction for laterized concrete will also be
important.
According to Ogork et al. (2014) prediction of concrete
strength has been an active area of research and a considerable
number of studies have been conducted on prediction of
strength of concrete at various ages with high level of
accuracy. But all this while, concentration has been on
conventional concrete. It is against this background that this
paper is aimed at producing strength models for laterized
concrete for design prediction.
2. Materials and Methods
2.1. Materials
Ordinary Portland cement produced in Nigeria (Dangote
brand), with a specific gravity of 3.14 was used. Sharp Sand
was obtained from Gidan-kwano area of Niger State, Nigeria,
with a specific gravity of 2.61, bulk density of 1416.67Kg/m3;
moisture content of 10.02% was used. The particle size
distribution of the sand shown in Figure 1 indicates that it is
within the grading limits specified by BS 882: 1992 and
therefore acceptable as standard sand for making concrete.
The lateritic material use was obtained from Julius Berger
borrow pit at Maikunkele in Niger State, Nigeria. The specific
gravity is 2.62, moisture content is 20.42% and bulk density is
1250Kg/m3. The coarse aggregate was crushed granite of
nominal size of 20 mm with a specific gravity of 2.54,
moisture content of 21.94%, and bulk density of
1260.56Kg/m3, obtained from Tri-Acta Quarry in Minna,
Niger State, Nigeria. The particle size distribution shown in
figure 2 also indicates that it is within the grading limits
specified by BS 882: 1992.
2.2. Mix Design
A mix of 1:1.5:3 (cement, fine aggregate and coarse aggregate)
corresponding to concrete grade 30 was used for this research
because it is the most suitable mix for structural application
(Balogun & Adepegba, 1982). The percentage replacement of
sand with laterite is 0% and 20% substitute of fine aggregate
and 0.65 water/cement ratio was used. The 0% replacement
serves as the control. Quantities of used engine oil added as
admixture to the concrete were 0%, 0.075%, 0.15%, 0.30%,
and 0.60% of the weight of cement. Again 0% UEO addition
serves as control.
The Absolute Volume method was adopted for the
computation of the quantities of materials required. Table 1
gives the materials batch weights for the five mixes for 20%
of laterite substitution for fine aggregate.
Table 1. The Weight of Constituent Material for Each Batch with 20% Laterite
(%) of
UEO
Mix
proportion
W/C
Ratio
Cement
(kg)
Sand
(kg)
Laterite
(kg)
Coarse
agg. (kg)
Water
(kg)
UEO
(kg)
0
0.075
0.15
0.30
0.60
1:1.5:3
1:1.5:3
1:1.5:3
1:1.5:3
1:1.5:3
0.65
0.65
0.65
0.65
0.65
43.95
43.95
43.95
43.95
43.95
56.02
56.02
56.02
56.02
56.02
14.01
14.01
14.01
14.01
14.01
135.42
135.42
135.42
135.42
135.42
28.50
28.50
28.50
28.50
28.50
0
0.033
0.066
0.132
0.264
2.3. Compressive and Splitting Tensile Strength Tests on
UEO-Laterized Concrete Mixtures
The compressive and splitting tensile strengths of laterized
concrete admixed with UEO were carried out in accordance
with BS 1881 Part 116 (1983) and BS 1881 Part 117 (1983)
respectively. The samples were cast in steel moulds of 100
mm cubes and 150 mm diameter by 150 mm long cylinders
for compressive and splitting tensile strength respectively.
They were cured in water for 7, 21, 28, 56 and 90 days. A
total of 150 samples were tested for both compressive and
splitting tensile strength tests and at the end of every curing
cycle, 3 samples were crushed using the ELE 2000 KN
capacity mechanically operated hydraulic compression
testing machine.
2.4. Statistical Modeling of the UEO-Laterized Concrete
Mixtures
Statistical models were developed from experimental data
using MINITAB software to predict strength behavior of
UEO-Laterized concrete at 20 % laterite replacement of sand.
In developing the compressive strength and splitting tensile
strength prediction models of the laterized concrete, two
effects were considered; (i) influence of used engine oil
content and (ii) influence of curing on the laterized concrete
strength. The software generates model equations and graphs
that would best fit the experimental data. A comparison is
then made between the experimental data and data generated
by the models and the error difference evaluated.
3. Results and Discussion
The results of the investigations are presented and discussed
below:
3.1. Compressive and Splitting Tensile Strengths
The compressive and splitting tensile strength development of
UEO-concrete is illustrated in Figures 1 and 2 respectively.
American Journal of Civil and Structural Engineering (2015) 11-15
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Similarly, it is also observed in Figure 2 that the splitting
tensile strength increased with age of curing but decrease with
increase in UEO content. The splitting tensile strength of
control laterized concrete was higher than that of
UEO-Laterized concrete at all ages. The 28 days splitting
tensile strength of the control was 1.76N/mm2 while the
reduction in the strength of UEO-laterized concrete ranged
from 0.56 – 6.48% of control, with laterized concrete
containing 0.075 and 0.60% UEO content having the least and
maximum strength reduction respectively.
3.2. Regression Models for UEO-Laterized Concrete
The regression equations generated for compressive and
splitting tensile strengths of UEO-Laterized Concrete models
are given in equations 1and 2, respectively.
Figure 1. Compressive Strength Development of UEO-Laterized
Concrete
Figure 2. Splitting Tensile Strength Development of
UEO-Laterized Concrete
It can be observed in Figure 1 that compressive strength
increase with age of curing but decrease with increase in UEO
content at all ages. The 28 days compressive strength of
laterized concrete without UEO was 28.78 N/mm2 which is
less than 30 N/mm2 (the characteristic strength for grade 30
for normal concrete) but more than 25N/mm2 (the
characteristic strength for grade 25 for normal concrete). This
means that grade 30 normal concrete is equivalent to grade 25
laterized concrete. And since the 28 days compressive
strength of UEO-laterized concrete with up to 0.3% UEO
content exceeded the characteristic strength of 25N/mm2 for
grade 25 laterized concrete, 0.3% UEO would be considered
as the optimum percentage replacement. The reduction in the
28 days compressive strength of UEO-Laterized concrete
ranged from 0.07 – 15.88% of control at UEO content of
0.075 – 0.60%, with the highest reduction occurring at 0.60%.
The decrease in compressive strength of laterized
concrete could be due to the fact that the surface areas of the
binder (cement) were coated with oil, such that physical bond
formation between cement paste and the aggregates (sand,
laterite and coarse aggregates) was hindered thereby slowing
down the rate of strength development especially at the early
ages (Oyinuola, 2009).
fc = 9.03 - 0.85 UEO + 6.25 A
(1)
ft = - 0.12 - 0.10 UEO + 0.71 A
(2)
Where; fc is laterized concrete compressive strength, ft is
laterized concrete splitting tensile strength, UEO and A are
Used Engine Oil content and curing age of samples,
respectively.
At 0.05 level of significance, from the regression analysis,
P-value = 0.001 for UEO content and 0.000 for age of curing
of laterized concrete, and shows that both variables are highly
significant (P < 0.05) and indicates that the variation in the
laterized concrete compressive strength is caused by UEO
content and age of curing. In the case of splitting tensile
strength of laterized concrete, the regression analysis shows
P-value = 0.000 for both UEO content and age of curing of
laterized concrete, and also indicates that both variables are
very significant and influence the variation of splitting tensile
strength of laterized concrete. The coefficient of
determination, (R2) is 0.899 and 0.925 for compressive
strength and splitting tensile strength, respectively and
implies that the variation of laterized concrete strengths is
significantly dependent on the variations of UEO content and
age of curing. The residual and normality plots (Figures. 3 and
4 5 and 6) were drawn for the compressive and splitting
tensile strengths of laterized concrete to further examine how
well the models fit the data used. It was observed that there
were few large residuals (Elinwa & Abdulkadir, 2011) and
limited apparent out-lier (Razak & Wong, 2004). This
confirms that the models are adequate for strength prediction.
14
American Journal of Civil and Structural Engineering (2015) 11-15
Figure 3. Residual Versus Fittde Values for Compressive Strength of UEO-Laterized Concrete
Figure 4. Normal Probability of Residuals for Compressive Strength of UEO-Laterized Concrete
Figure 5. Residual Versus Fitted Valuse for Splitting Tensile Strength of UEO-Laterized Concrete
American Journal of Civil and Structural Engineering (2015) 11-15
15
Figure 6. Normal Probability of Residuals for Splitting Tensile Strength of UEO-Laterized Concrete
4. Conclusion
I.The compressive strength and splitting tensile strength of
laterized concrete decrease with increase in UEO content. The
highest reduction in the 28 days compressive strength of
UEO-Laterized concrete was 15.88% of control at UEO
content of 0.60%.
II. For structural application, 0.3% UEO should be used
as the optimum percentage replacement in laterized concrete
to act as chemical retarder suitable for hot weather concreting
and long haulage of ready mixed laterized concrete.
III. The regression models for UEO-laterized concrete
with R2 values of 0.899 and 0.925 for compressive strength
and splitting tensile strength respectively were good for
prediction of laterized concrete strengths.
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