EEFECT OF CEMENT ON ASPHALT - EMULSION ... Journal of Scientific Research and Innovative Technology...
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International Journal of Scientific Research and Innovative Technology ISSN: 2313-3759 Vol. 3 No. 5; May 2016
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EEFECT OF CEMENT ON ASPHALT - EMULSION STABILIZED
LATERITIC SOILS
B.D. OLUYEMI – AYIBIOWU
Department of Civil and Environmental Engineering
The Federal University of Technology, Akure, Ondo State, Nigeria
ABSTRACT
The influence of the physical characteristics and chemical compositions of three selected lateritic soils on
their engineering behaviour in the natural untreated state and their response to treatment with asphalt
emulsion mixed with cement in varied proportions was investigated in the laboratory. Asphalt emulsion, Colax
A was added to the collected lateritic samples in their natural state and tested, after which small percentages
of cement in varied proportions was used to modify the properties of the asphalt emulsion treated lateritic
samples to evaluate the influence of cement and to determine the best mix ratio. Test results show that adding
asphalt emulsion to the samples generally increase their strength, the rate of increase depending on the type
of soil. Beneficial results were further obtained by adding small percentages of cement to the asphalt emulsion
for treating all the soil samples especially the highly plastic soils which did not respond favourably with only
the use of asphalt-emulsion, thus bringing to usefulness the technology of improving the strength of locally
available weak soils by pre-treating the soil with small amounts of cement prior to the addition of asphalt-
emulsion for increased strength characteristics.
Key Words: Laterites, Lateritic soils, Soil samples, Stabilization, Cement, Asphalt-Emulsion, Mixes,
Laboratory, Tests, Results, Strength.
1.0 INTRODUCTION
Laterites and lateritic soils have over the years been given increased attention by soil engineers because of
their wide spread distribution and engineering applications. Laterites, though abundant in many countries have
varied properties from place to place. This makes their performance diverse and unpredictable (Gidigasu,
1976). These varied properties have brought limitations to their use on some construction sites. Many of these
Limitations have been overcome by the addition of stabilizing agents to improve their properties or by various
other means of soil improvement.
Some of the stabilization methods include the use of cement, lime, fly ash and bitumen depending on the type
of soil and site condition (British Lime Association Digest, 1999). Portland cement has been used with great
success to stabilize natural soil because almost all soils respond to treatment with cement. However, the
chemical conditions of some soils which can inhibit the normal hardening of cement or lead ultimately to loss
of durability or high construction cost for the highly plastic soils have limited their use. Bituminous
stabilization is also being in use for construction purposes all over the world, and so is hydrated lime.
Hydrated lime in its own case increases soil strength primarily by pozzolanic action with the formation of
cementation materials especially in granular materials or lean clays (Little et.al, 2003, Owolabi et.al, 2004).
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Asphalt-emulsion is a liquid mixture which contains asphalt cement, water and an emulsifying agent for road
construction and maintenance and has received wide acceptance by engineers because of their performance
and economic advantage (Coyne. 1976). Asphalt emulsion does not require petroleum to soften it and no heat
is applied during use, thereby contributing to energy saving. It reduces atmospheric pollution because there are
little or no hydrocarbon emissions from it (Coyne and Ripple, 1975). It also has the ability of coating damp
aggregate surfaces. They are widely available in variety of types and there is potential cost savings by the use
of less fuel (Koch, 2002). In the United States, attention had been directed to fuel savings by using asphalt
emulsion instead of cutback asphalt whereby a huge amount of petroleum solvents could be saved annually by
such substitution (American Virtual Productions, 1997.
Generally, a certain type of stabilization activity may not be very successful for all the soils. A soil may be
mixed with one additive to improve its quality in one phase and in a second phase be mixed with another
additive to achieve desired strength. Mixtures of two stabilizers can therefore be used to stabilize soils in that
one of the stabilizers will compensate for the effectiveness of the other on a certain property of the treated
material (National Association of Australia State Road Authorities, 1986).
This paper thus presents laboratory study on the use of cement with asphalt emulsion to stabilize lateritic soils
for use as road foundation and construction materials. This will contribute to sustainable road maintenance and
development.
2.0 MATERIALS AND PROCEDURES
2.1 Materials
The three lateritic soils designated as samples A, B and C used for this work were collected along Ado-Ekiti -
Ikare road, which is a Federal road linking Ekiti with Ondo state in SouthWestern part of Nigeria. Fig. 1 is the
map of Nigeria showing the study area.
For the study, Asphalt-emulsion was used in proportions of 2, 4, 6 and 8% for soil asphalt emulsion mixes.
Portland cement, Type 1 was used in proportions of 1/2, 1 and 2% for the cement modification. The asphalt-
emulsion used is Colax A obtained from Ondo State Asphalt Company, Akure, Ondo State, Nigeria.
2.2 Procedures
The lateritic soil samples in their natural state after collection were stored in polythene bags to prevent
moisture loss. Deleterious materials such as roots were removed prior to their use after which they were air-
dried, broken done with mortar and pestle, and then passed through a No 10 sieve to remove large particles.
To correlate the engineering characteristics of the natural samples with treated ones, laboratory tests such as
Particle size distribution, Atterberg limits, specific gravity, compaction, California Bearing Ratio (CBR) and
unconfined compressive strength, (UCS) were performed on the natural samples.
To improve the engineering characteristics of the soil samples, asphalt emulsion pretreated with cement were
used to mix the soil samples. Mixing of samples was done manually at the optimal moisture content as
obtained from compaction tests. For the cement treated samples, varied percentages of cement were first
mixed with the samples after which asphalt-emulsion with water was added. Specimens were molded in CBR
moulds using the modified AASHTO compaction method for moisture -density relations and CBR values. For
compressive strength determination, unconfined compression test method was used.
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For each percentage of additives, average of four specimens was used to obtain each point on the moisture -
density relation and CBR curves. Nine specimens were used for the UCS; three each for 7, 14 and 28 - day
strength tests. After casting, the specimens were wrapped in nylon bags for curing after which testing for
relevant characteristics were carried out using standard methods. The strength values reported are average of
results of three test specimens for each mixture.
3.0 RESULTS AND DISCUSSION
3.1 Physical Characteristics of Natural Samples
Table 1 shows the Atterberg limits and the textural and chemical composition of the soil samples. The Liquid
limit ranged between 31-55% with plasticity indices between 9 and 26%. The different percentages passing
the number 200 sieves are 34.2%, 32% and 55.5% tor samples A, B and C respectively. The maximum dry
densities are 1.80mg/m3 for samples A and B, and 1.70mg/m
3for sample C with optimum moisture contents of
12.3%, 15.3% and 16.3% for samples A, B and C respectively. The CBR values are 20, 18 and 8% with 28-
day UCS values of 1.20MN/m2, 0.86MN/m
2 and 0.68MN/m
2for samples A, B and C respectively. The low
CBR and UCS values of the three samples indicate their unsuitability for use directly as highway materials
unless otherwise improved.
3.2 Cement Modified Asphalt-Emulsion Stabilized Soils
Addition of cement to lateritic soil samples treated with asphalt emulsion resulted in increased strength over
that of the natural soil samples. This is in accordance with the work of Coyne (1976) which shows that
addition of small percentages of cement will improve the early curing strength of emulsified asphalt mixes.
The results are as shown on Tables 2, 3 and 4 and in Figs. 2 to 10 for samples A. B and C respectively.
3.2.1 Compaction Characteristics
Compaction test results show increase in OMC and MDD of soil-cement-asphalt-emulsion combinations.
Sample A increased from 12.3% OMC at 0 % additive content to 16.3% with 8% asphalt-emulsion modified
with 2% cement. The MDD also increased from 1.80mg/m3 at 0% additive to 1.89mg/m
3 using 2% asphalt-
emulsion with 2% cement content. Further increase in the quantity of additive led to a reduction in the MDD
to 1.78mg/m3 at 8% asphalt-emulsion modified with 2% cement. The OMC of sample B also decreased from
15.3% natural value to 13.2% at 8% emulsion with 0.5% cement but increased with increase in cement
content. Using 8% emulsion with 2% cement gave an OMC of 16.3% and MDD of 1.64mg/m3.
For soil sample C, 4% asphalt-emulsion mixed with 0.5% cement gave the highest MDD value of 1.69mg/m3
at OMC of 16.3%. Increasing the quantity of emulsion led to a reduction in the degree of compaction with an
OMC of 16.6% and MDD of 1.56mg/m3 at 8% emulsion mixed with 2% cement.
3.2.2 Strength Characteristics
To determine the effect of cement on asphalt-emulsion stabilized samples, CBR and UCS tests were carried
out to ascertain the responses of the materials to stabilization. The results are shown on Tables 2, 3 and 4 with
the variations shown in Figs. 2 to 10 for the treated samples.
Addition of 0.5% cement to each percentage of asphalt-emulsion for sample A improved the strength
characteristics. With 2% asphalt emulsion, the CBR value increased from 85% to 145% at 6% emulsion
content. This later reduced to a CBR value of 100% at 8% emulsion content. Adding 1% cement to the varied
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percentages of emulsion brought the CBR value to a maximum of 150% with 6% emulsion, but reduced to
120% at 8% emulsion. Mixing 2% cement for the modification gave CBR values of 120% and 200% with 2%
and 4% emulsion contents respectively. On further addition of asphalt-emulsion, reduction in CBR values
resulted gradually to 125% with 8% emulsion.
For sample B, the CBR values also increased on the addition of cement to asphalt-emulsion mixes. With 0.5%
cement, a maximum CBR value of 95% resulted with 6% asphalt-emulsion, and later reduced to a CBR value
of 80% with 8% emulsion content. Adding 1% cement to modify the asphalt-emulsion gave maximum CBR
value of 119% at 6% asphalt-emulsion and 80% at 8% emulsion content. Pre -treating the emulsion with 2%
cement led to CBR values of 100% and 140% at 2% and 4% emulsion contents respectively. Mixing 2%
cement with 6% and 8% emulsion led to reduction in CBR values to 125% and 115% respectively.
Due to the high plasticity of sample C, maximum CBR value was obtained by using 2% cement with 8%
asphalt -emulsion. The result gave a maximum of 120% CBR value.
Considering Unconfined Compressive Strength test (UCS), the treated samples were tested at 7, 14 and 28
days to determine the effect of curing age on the strength of samples treated. The result is as shown on Tables
2, 3 and 4. For sample A, the result gave UCS strengths of 1.02 MN/rn2 at 7-day and 1.34 MN/m
2 at 28 days
for 2 % asphalt-emulsion modified with 0.5% cement. Treating with 4% emulsion gave a 7 and 28-day UCS
of 3.9MN/m2 and 4.32MN/m
2 respectively. Increasing the emulsion content to 6% reduced the UCS to a 7 and
28-day values of 3.0 MN/m2 and 3.6MN/m
2. At 8% emulsion, a further reduction in UCS to 2.2MN/m
2 7- day
strength and 2.53MN/m2
28-day strength were obtained.
Modifying sample A with 1% cement added to 4% asphalt-emulsion gave a maximum UCS of 4.0MN/m2 at 7
day and 4.66MN/m2 at 28 day strength. With 6% asphalt-emulsion, this decreased to 3.5MN/m
2 at 7-day and
3.80MN/m2 at 28-day; and with 8% asphalt-emulsion, it further reduced to 2.7MN/m
2 7-day and 2.88MN/m
2
28-day strength. Varying emulsion contents with 2% cement with 4% asphalt-emulsion yielded a maximum 7
and 28 - day UCS of 4.85MN/m2 and 5.12 MN/m
2. At 6% emulsion, the result gave 7-day strength of
3.8MN/m2 and 28-day strength of 4.21MN/m
2. While with 8% emulsion and 2% cement, the UCS reduced to a
7- and 28- day strengths of 2.86MN/m2 and 2.98MN/m
2 respectively.
For sample B, using 0.5% cement for modifying the soil samples treated with 2% emulsion content gave 7-
and 28-day UCS of 0.87MN/m2 and l.02MN/m
2; Maximum UCS was obtained with pre-treating with 6%
asphalt-emulsion. This gave 3.01MN/m2 28-day strength, which reduced to 2.41MN/m
2 with 8% emulsion
content. Mixtures of asphalt-emulsion with 1% cement increased the UCS from 7-day strength of 0.96MN/m2
with 2% emulsion content. Further increase in emulsion content to 8% led to a reduced 7-day UCS of
2.5MN/m2 and 2.75MN/m
2 28-day strength. Using 2% cement with 2% emulsion gave a 7-day UCS of
2.9MN/m2 and 3.34MN/m
2 at 28-day. This increased with 4% asphalt-emulsion to a UCS of 3.5MN/m
2 at 7-
day and 3.80MN/m2 at 28-day but later reduced with 8% asphalt-emulsion to 2.60MN/m
2 7-day strength and
2.80MN/m2 28-day strength.
The UCS of sample C also increased on addition of 0.5% cement to the asphalt-emulsion mixes but with a low
range of increment due to its high clay content. It increased from a 7-day strength of 0.58MN/m2 to
1.60MN/m2 by using 2% and 8% asphalt-emulsion contents respectively. Adding 1% cement to 2% emulsion
gave 7-day strength of 0.75MN/m2 and 1.70MN/m
2 with 8% emulsion. Mixtures of emulsion with 2% cement
and 2% asphalt-emulsion gave 7 and 28-day UCS of 1.86MN/m2 and 2.54MN/m
2. This increased to 7-day
UCS of 2.80MN/m2 and 28-day UCS of 3.40MN/m
2 with 4% emulsion and 2% cement. With further increase
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in asphalt-emulsion content, an increased UCS resulted to maximum values of 3.70MN/m2 at 7-day and
4.21MN/m2
28-day values with 8% asphalt-emulsion content.
4.0 CONCLUSION
The results of the investigation presented in this paper showed that beneficial effects were obtained by adding
small amounts of cement to soil-asphalt-emulsion mixes, and specifically the results led to the following
conclusion,
(i) Pre-treatment of fine grained soils with cement facilitates mixing in of asphalt-emulsion and hence
improves workability
(ii) Addition of cement increases the strength of soil-asphalt-emulsion mixtures.
iii) Curing of treated samples increases their compressive strengths.
(iv) For treated samples, there is an optimum amount of additive which gives a maximum compressive
strength depending on the type of soil.
(v) Addition of cement to asphalt-emulsion highly favours soils of high plasticity that does not respond
appreciably with only asphalt-emulsion.
(vi) Modification of asphalt- emulsion with small amounts of cement will lead to reduction in cost of
stabilized soils especially the clay soils which will require a high quantity of cement for their treatment.
(vii) It has been possible to obtain samples of soils stabilized with small percentages of cement added to
asphalt-emulsion and possessing strengths as those of samples stabilized with higher amounts of cement.
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Table 1: Characteristics of Natural Soil
Soil A B C
Textural composition %
Gravel 3.4 5.8 0.5
Sand 62.4 62.2 44
Fine 34.2 32 55.5
Classifications:
British Soil Classification System, BSCS Very clayed
Sand
Clay of intermediate
Plasticity
Highly Plastic Soil
American Association of State Highways and
Transport Officials, AASHTO
A-2-5 A-2-7 A-7-6
Physical properties:
Liquid limit, % 31 46 55
Plastic limit, % 22 31 29
Plastic index, % 9 15 26
Max Dry Density, Mg/m3 1.8 1.8 1.7
Optimum Moisture Contents, % 12.3 15.3 16.3
Chemical Composition:
pH 5.6 5.4 4.8
Si O2 56.81 56 50.5
Al O3 26.22 26.11 30.93
Fe2 O3 0.88 0.1 0.11
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Table 2: Summary Results of sample A Treated with Asphalt-emulsion and Cement
Emulsion:
Cement (%) OMC % MDD Mg/m3
CBR % UCS 7days USC 14 days UCS 28days
0 12.3 1.8 20 0.85 1 1.2
2:0.5 14.8 1.86 85 1.02 1.2 1.34
4:0.5 15 1.84 120 3.96 4.19 4.32
6:0.5 15.2 1.82 145 3 3.25 3.6
8:0.5 15.4 1.79 100 2.2 2.41 2.53
0 12.3 1.8 20 0.85 1 1.2
2:1 15 1.83 105 2.81 3 3.25
4:1 15.4 1.81 125 4 4.25 4.66
6:1 15.8 1.77 150 3.5 3.72 3.8
8:1 16.1 1.76 120 2.7 2.81 2.88
0 12.3 1.8 20 0.85 1 1.2
2:2 14.8 1.89 120 3.56 3.73 3.9
4:2 15.6 1.83 200 4.85 5 5.12
6:2 15.8 1.82 150 3.8 3.98 4.21
8:2 16.3 1.78 125 2.86 2.9 2.98
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Table 3: Summary Results of Sample B Treated with Asphalt-emulsion and Cement
Table 4: Summary Results of Sample C Treated with Asphalt-emulsion and Cement
EMULSION:
CEMENT %
OMC
% MDD Mg/m3
CBR
% UCS 7days USC 14 days UCS 28days
0 15.3 1.8 18 0.5 0.72 0.85
2: 0.5 13.4 1.74 50 0.87 0.92 1.02
4: 0.5 13.8 1.73 85 2.35 2.79 2.85
6: 0.5 13.1 1.72 95 2.7 2.87 3.01
8: 0.5 13.2 1.7 80 2 2.36 2.41
0 15.3 1.8 18 0.5 0.72 0.85
2: 1 13.6 1.72 75 0.96 1.02 1.16
4: 1 15.4 1.7 98 3.19 3.3 3.46
6: 1 14.2 1.63 119 2.8 2.93 3.01
8: 1 15 1.6 80 2.5 2.61 2.75
0 15.3 1.8 18 0.5 0.72 0.85
2: 2 14.4 1.7 100 2.9 3 3.34
4: 2 15.3 1.68 140 3.5 3.65 3.8
6: 2 15.8 1.66 125 3.01 3.3 3.38
8: 2 16.3 1.64 115 2.6 2.72 2.8
EMULSION:
CEMENT ( %) OMC % MDD Mg/m3 CBR % UCS 7days USC 14 days UCS 28days
0 16.3 1.7 8 0.41 0.5 0.68
2 15.2 1.63 25 0.58 0.95 1.2
4 16.3 1.69 45 0.9 1.16 1.28
6 16.6 1.63 50 1.5 1.65 1.8
8 16.3 1.54 80 1.6 1.8 1.87
0 16.3 1.7 8 0.41 0.5 0.68
2 15.6 1.61 30 0.75 1 1.18
4 15.6 1.6 50 0.95 1.07 1.29
6 16.1 1.58 70 1.2 1.38 1.5
8 16.5 1.55 90 1.7 1.83 s1.95
0 16.3 1.7 8 0.41 0.5 0.68
2 15.8 1.65 40 1.86 2 2.54
4 15.9 1.63 90 2.8 3.15 3.4
6 16.3 1.59 105 3.05 3.2 3.5
8 16.6 1.56 120 3.7 4 4.21
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Figure 1: Map of Nigeria Sho
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howing Ondo and Ekiti State, Nigeria
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FIG.2: Variation of OMC, MDD, CBR a
Modified with ½ % Cement
Fig. 3: Variation of OMC, MDD, CBR a
Asphalt Emulsion M
0
2
4
6
8
10
12
14
16
18
0 2 4
0
2
4
6
8
10
12
14
16
18
0 2 4
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and 28-day UCS of sample A Stabilized with 0-8
and 28-day UCS of Sample A Stabilized with 0-
Modified with 1% Cement
6 8 10
OMC %
MDD Mg/m3
UCS 28days
CBR %
6 8 10
OMC %
MDD Mg/m3
UCS % 28days
CBR %
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8% Asphalt Emulsion
-8%
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Fig. 4: Variation of OMC, MDD, CBR a
Asphalt Emulsion M
Fig. 5: Variation of OMC, MDD, CBR a
Asphalt Emulsion M
0
2
4
6
8
10
12
14
16
18
0 2 4
0
2
4
6
8
10
12
14
16
18
0 2 4
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and 28-day UCS of Sample A Stabilized with 0-
Modified with 2% Cement
and 28-day UCS of Sample B Stabilized with 0-
Modified with ½ % Cement
6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days
6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days
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-8%
8%
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Fig. 6: Variation of OMC, MDD, CBR a
Asphalt Emulsion M
Fig. 7: Variation of OMC, MDD, CBR a
Asphalt Emulsion M
0
2
4
6
8
10
12
14
16
18
0 2 4
0
2
4
6
8
10
12
14
16
18
0 2 4
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and 28-day UCS of Sample B Stabilized with 0-
Modified with 1% Cement
and 28-day UCS of Sample B Stabilized with 0-
Modified with 2% Cement
6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days
6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days
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8%
8%
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Fig. 8: Variation of OMC, MDD, CBR a
Asphalt Emulsion M
Fig.9: Variation of OMC, MDD, CBR an
Asphalt Emulsion M
0
2
4
6
8
10
12
14
16
18
0 2 4
0
2
4
6
8
10
12
14
16
18
0 2 4
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and 28-day UCS of Sample C Stabilized with 0-
Modified with ½ % Cement
and 28-day UCS of Sample C Stabilized with 0-8
Modified with 1% Cement
6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days
6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days
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8%
8%
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Fig.10: Variation of OMC, MDD, CBR and 28-day UCS of Sample C Stabilized with 0-8%
Asphalt Emulsion Modified with 2 % Cement
5.0 REFERENCES
American Virtual Productions (1997); Specialty Emulsions, Site Re-built and Maintained, American Virtual
Productions Co, USA
British Lime Association (1999): Improving Poor Ground Conditions, Lime and Cement Stabilization of weak
soils, Aggregates Advisory Services, Digest No, 058
Coyne, L.D (1976): Emulsion Stabilization Mix Design, Technical Paper No. 172, Chevron Asphalt Company,
San Francisco
Coyne, L.D and Ripple R.M (1975): Emulsified Asphalt Mix Design and Construction, Technical Paper,
Annual Meeting of Association of Asphalt Paving Technology
Dallas N. Little, Eric H. Males, Jan K, Prusmski and Barr Stewart (2003): Cementitious Stabilization, Report
of Committee on Cementitious Stabilization, A2J01, Transport Research Board.
Gidigasu M.D (1976): Laterite Soil Engineering, Pedogenesis and Engineering Principles, Elsevier Scientific
Publishing Company, Amsterdam.
Koch Materials Company (2002): Emulsified Asphalt, Koch Pavement Solutions, USA
National Association of Australia State Road Authorities (1986): Guide to Stabilization in Road works, TRRL,
Technical Information and Library Services, Sydney.
Owolabi, A.O, Oluyemi-Ayibiowu, B.D and Aderinola O.S (2004): Effect of Moisture on the Strength of
Lime Stabilized Lateritic Soils (A Case Study of Ojota, Lagos), Journal of Civil Engineering, Pp 10-15
0
2
4
6
8
10
12
14
16
18
0 2 4 6 8 10
OMC %
MDD Mg/m3
CBR %
UCS 28days