International Journal of Applied Engineering Research ISSN 0973-4562 Volume 9, Number 21 (2014) pp. 9655-9665 © Research India Publications http://www.ripublication.com
Geotechnical Properties of Lateritic Soils Stabilized with Cement-Bamboo Leaf Ash Admixtures Bello, Afeez Adefemi; Ige, J. A., Ibitoye, Grace Ibironke Department of Civil Engineering, Faculty of Engineering, Osun State University, Osogbo, PMB 4494, Nigeria E–mail:
[email protected]
Abstract This research was carried out to study the effect of cement with bamboo leaf ash admixtures stabilization on lateritic soil samples. Preliminary tests were performed on three samples, A, B, and C for identification and classification purposes included natural moisture content determination, specific gravity tests, grain size analysis and Atterberg limits tests. Geotechnical property tests (compaction and California bearing ratio (CBR)) were also performed on the samples, both at the stabilized and unstabilized states by adding 2%, 4%, 6% and 8% of both cement and bamboo leaf ash (BLA) by weight of sample to the soils. The maximum dry density (MDD) are 17.45 kN/m3, 16.45 kN/m3 and 16.3 kN/m3 and optimum moisture content (OMC) of 12.5%, 17.5%, and 14% for samples A, B, and C respectively at 0% stabilization (at the natural state). The MDD gradually decreased to 4% stabilization state while it suddenly increased at the 6% stabilization state. MDD decreases non-uniformly for the remaining samples B and C. Result shows increasing OMC and decreasing MDD as the percentages of cement content and bamboo leaf ash admixture increased, for all the tests carried out for the three samples. This was due to the agglomeration of large particles (sand and gravel) occupying larger space with a corresponding drop in dry density and because of extra water required for the hydration of cement and the pozzolanic reaction of bamboo leaf ash and respectively. The values of the California Bearing Ratio increase slightly from 20.88, 10.34 and 10.33 to 23.24 (at 8% cement-BLA), 19.95 (at 8% cement-BLA) and 14.89% (at 6% cement-BLA) for samples A, B and C respectively. There is no significant influence of the stabilizer on the soil samples used, hence the need for further research on the samples required. Keywords: bamboo leaf ash, cement, lateritic soils, pozzolanic, stabilization,
Paper Code: 26710 - IJAER
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Introduction Some lateritic soils have been found to be problematic in the course of construction due to their poor engineering properties such as high swelling and shrinkage response to water volume ratio, high permeability and compressibility of the soil mass, low bearing capacity especially in the foundation soil, etc. (Chndra, 1987; Bello, 2011; Bello and Adegoke, 2013). The tendency for laterite gravels to be gap-graded with depleted sand-fraction, to contain a variable quantity of fines, and to have coarse particles of variable strength which breakdown, limits their usefulness as pavement and other construction materials; especially on roads with heavy traffic and adverse moisture conditions or heavy constructions. To improve on the above deficiencies, and consequently to improve on their field performance characteristics, they need to be stabilized. Stabilization has been defined as any process by which a soil material is improved and made more stable (Thagesen, 1989). It was also described as the treatment of natural soil to improve its engineering properties (Garber and Hoel, 2000). In general, soil stabilization is the process of creating or improving certain desired properties in a soil material so as to render it stabled and useful for a specific purpose. Soil stabilization may be broadly defined as the alteration or preservation of one or more soil properties to improve the engineering characteristics and performance of a soil. It is required when the soil available for construction is not suitable for the intended purpose. The goals of stabilization are therefore to improve the soil strength, to improve the bearing capacity and durability under adverse moisture and stress condition, controlling dust, soil waterproofing, and to improve the volume stability of a soil mass. Engineers are responsible for selecting or specifying the correct stabilizing material, method, technique, and quantity of material required. Many procedures have been outlined for making correct decisions in selection but most of them are not precise. Soils vary throughout the world, and the engineering properties of soils are equally variable. The key to success in soil stabilization is soil testing. The method of soil stabilization selected should be verified in the laboratory before construction and preferably before specifying or ordering materials (Olugbenga and Akinwole, 2010). When the mechanical stability of a soil cannot be obtained by combining materials, it may be advisable to order stabilization by the addition of lime, cement, bituminous materials or special additives. Cement stabilization is most used in road construction especially when the moisture content of the subgrade is high. Portland cement is the most important hydraulic cement utilized extensively in various types of cement stabilization of lateritic soils. Cement acts as a binder and provides the much desired hardening and strengthening properties. The addition of cement also increases compressive strength, the resistance of lateritic soils to freezing and thawing, wetting and drying. It also affects the particle size distribution of the soils by increasing the size of fine particles. Conventionally, portland cement have been used to appreciably improve the properties of soils (Ola 1975; 1983; Osula 1989; Berthelot et al 2005; Gadzama, 2009). Gadzama (2009) also established that 4% cement can be recommended as an optimal content to stabilize soil from parts of Northern Nigerian. Ola (1975) noticed an increase in the compressive strength of lateritic soils with
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cement content. Curtis et al (2009) stated that full-depth reclamation and cement stabilization enabled significant volumes of in-place granular materials to be reclaimed and strengthened while allowing for the installation of a woven geotextile and sand drainage system over a wetted-up subgrade in a more cost-effective and sustainable construction manner. Data about the influence of Cement-Bamboo leaf ash on lateritic soil is lacking hence this study is aimed at investigating the effect of Cement–Bamboo leaf ash admixture on lateritic soil samples.
Materials and Method Materials used Soil The soil sample used for this research was a reddish brown lateritic soil (latitude 7o45’N and longitude 4o33’E) collected by disturbed sampling from a borrow pit at a depth of between 1.0m and 2.0m at Osun State University Engineering complex cafeteria, Osogbo, Osun State, Nigeria. A study of the soil and geological maps of Nigeria after Akintola (1982) and Areola (1982), respectively, show that the study area lies within southwestern Nigeria basement complex which forms part of the African crystalline shield. The basement complex is composed predominantly of folded gneisses, migmatite, schist and quartzite of the Precambrian age. The soil samples were collected in large-to -medium-sized bags and thereafter transported to the Soil Mechanics Research Laboratory of the Department of Civil Engineering, Osun State University, Osogbo, Osun State. Each soil sample was spread and allowed to air-dry under laboratory conditions. Bamboo leaves ash Bamboo leaves were collected from Olorunkemi Street, Oke - Baale area of Osogbo and burnt in an open atmosphere then, in the furnace for about 2hours at 600oC. It was burnt under controlled temperature of about 7000C- 8000C to obtain the ash. The rice husk ash was sieved through BS sieve No. 200 and the fractions passing through the sieve were used throughout the tests. The sieved ash was immediately stored in air tight containers to avoid pre-hydration during storage or when left in open air. Cement Portland cement which is the most common type of cement in general use in Nigeria was used as stabilizing agent in this study. Water Potable water was used for the preparation of the specimens at the various moisture contents. Method Index Properties Sieve analysis Hydrometer method was used to obtain values of the clay-size (percent < 0.002 mm)
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fraction of the soil constituents or particles. 250grammes of each soil samples was first measured and soaked using tap water for at least 2 days to ensure that the dry soil clods were softened. After soaking, the specimen was washed through BS No 200 (i.e., 0.075 mm) sieve. The material retained on the sieve after washing was collected into a small metal bowl, oven dried and sieved based on procedures outlined in BS 1377 (1990). Sieving was done in three replicates for each specimen. When the lateritic soil was treated with 2 - 12% rice husk ash by dry weight of soil at optimum moisture content (OMC), less than 10% of the material passed through BS No. 200 sieve, and therefore did not meet the minimum requirement for sedimentation analysis to be carried out. Specific gravity Specific gravity tests were conducted based on procedures outlined in BS 1377(1990) and Head (1992). The tests were carried out in three replicates. The specific gravity for each of the specimen was calculated using the expression (Head, 1992): (1) where ρL = density of liquid used (ρL was assumed to be equal to 1.000 g/ml for this purpose since distilled water was used); m1 = mass of density bottle (g); m2 = mass of bottle + dry soil (g); m3 = mass of bottle + soil + liquid (g); m4 = mass of bottle + distilled water only (g). Average of three measurements was calculated and recorded in each case. Specific gravity tests were repeated whenever any value differed from the average value by more than 0.03. Aterberg limits Aterberg limits tests which are otherwise known as plasticity tests were conducted on air-dried soils that had previously been passed through sieve with 425 μm aperture (Head, 1992). Distilled water was used throughout the tests to determine the plasticity of the soils. The liquid limit was determined with the use of the Casagrande apparatus in agreement with Clause 4.5, Part 2 of BS 1377 (1990). The five-point system was employed in order to obtain the actual liquid limit values of the soils. The plastic limit of each soil was estimated on the basis of procedures outlined in Clause 5.3, Part 2 of BS 1377 (1990). Portions of paste with water contents close to the liquid limit were used for plastic limit determination. The plasticity index of each soil was obtained as the difference between the liquid limit and plastic limit. The percentage linear shrinkage of each soil specimen was determined according to procedures in Clause 6.5, Part 2 of BS 1377 (1990). Moisture content determinations for the liquid and plastic limits tests were carried out by oven-drying in conformity with Clause 3.2, Part 2 of BS 1377 (1990). Compaction of Soil The standard Proctor (SP) compaction procedures were utilized during the tests. The SP compactions utilized 3 layers applying 27 blows each of a 2.5kg rammer falling from a height of 300mm using 1000cm3 mould.
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California bearing ratio The CBR were carried out in conformation with the recommendations of the Nigerian General Specifications for Roads and Bridges (Nigerian General Specification, 1997), which states that specimens be cured for 6 days unsoaked (that is, at a temperature of 25 ± 20C and relative humidity of 100 %) and immersed in water for 1 day before testing.
Results and Discussion The summary of results of the preliminary tests (grain size analysis, natural moisture contents, specific gravity, and Atterberg limits) obtained are presented and discussed below both at the natural state and at modified state is Table 1. Summary of the Properties of the Soils sample before stabilization Properties Natural Moisture content (%) Liquid Limit (%) Plastic Limit (%) Plasticity Index (%) Shrinkage Limit (%) Specific Gravity Percentage Passing 425µm Percentage Passing 75µm AASHTO Classification USCS Classification Colour
Sample A 21.13 47.37 33.74 13.63 10.36 1.98 63.02 50.52 A–7–6 ML Brown
Sample B 23.63 50.85 37.75 13.10 8.93 2.22 61.94 51.48 A–7–6 MH Reddish Brown
Sample C 24.07 40.82 24.20 16.62 8.22 2.49 66.46 52.42 A–7–5 CL Reddish Brown
The percentage of the soil samples passing BS Sieves 425µm and 75µm are shown in table 1 above. The percentage passing through 75µm BS sieve are 50.52%, 51.48%, and 52.42% for sample A, B, and C respectively. Based on the AASHTO classification systems, sample A has 19.92% of gravel, 29.56% of sand, and 50.52% of silt present in it and therefore belongs to A-7-6 group with the group name silty–clay materials. Sample B has 25.16% of gravel, 23.30% of sand, and 51.48% of silt and also classified as A–7–6 group. Sample C has 16.40% of gravel, 31.18% of sand, and 52.42% of silt and therefore belongs to the A–7–5 group because of its low plasticity. While the USCS classified sample A as having 6.67% of gravel, 42.72% of sand and 50.52% of silt and clay materials present in it with the group symbol ML and group name low plasticity gravelly silt. Sample B has 11.18% of gravel, 37.34% of sand and 51.48% of both silt and clay with the group symbol MH and group name high plasticity gravelly silt. Sample C also contains 6.16% of gravel, 41.42% of sand and 52.42% of both silt and clay with the group symbol CL and group name low plasticity gravelly lean clay (Holtz and Kovacs, 1981). The soil samples are fine-grained inorganic soils and are plastic in nature therefore render them unsuitable for construction works (Holtz and Kovacs, 1981).
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The liquid limits, plastic limits and the plasticity index of the soil samples at natural states are presented in Table 1 above while Table 2 below shows that of the stabilized state. Soils with liquid limit less than 30% are considered to be of low plasticity, those with liquid limit between 30% and 50% exhibit medium plasticity and those with liquid limit greater than 50% exhibit high plasticity. In sample A, the plasticity index (PI) increases with the percentage increase in stabilization except for 6% stabilization where there is a fall in the PI value, ditto for sample C, while it varies with the percentage stabilization in sample B. The PI is minimum at 6%, 4% and 6% stabilization for samples A, B, and C respectively. Hence, these percentages are recommended for optimum stabilization mix.
Fig. 1: Grain Size Distribution Curve of Unstabilized Samples (Samples A, B, & C)
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Table 2. Summary of the properties of the soil samples at the stabilized state Sample % Atterberg Limits Shrinkage Specific OMC MDD CBR (%) No Stabilization LL(%) PL(%) PI(%) Limit (%) Gravity (%) (kN/m3) (Unsoaked) 0% 47.37 33.74 13.63 10.36 1.98 12.50 17.45 20.88 2% 58.61 35.23 23.38 9.65 2.00 15.40 16.90 20.90 A 4% 61.11 37.41 23.7 7.60 2.23 16.00 16.20 21.36 6% 59.21 40.00 19.21 6.07 2.16 16.20 17.70 22.88 8% 62.40 38.44 23.96 4.65 2.34 16.00 17.4 23.24 0% 50.85 37.75 13.10 8.93 2.22 18.00 16.45 10.34 2% 59.80 37.35 22.45 7.50 2.21 18.60 15.40 10.91 B 4% 64.20 44.31 19.89 6.07 2.25 18.10 15.49 13.77 6% 63.74 30.38 33.36 6.00 2.27 17.80 15.33 14.32 8% 69.00 46.72 22.28 5.72 1.91 17.20 15.44 19.95 0% 40.82 24.20 16.62 8.22 2.49 14.00 16.30 10.33 2% 52.00 34.72 17.28 9.29 2.44 15.20 16.30 12.71 C 4% 60.00 41.68 18.32 8.93 2.34 16.00 15.90 12.20 6% 43.75 28.99 14.76 5.00 2.33 15.80 16.12 14.89 8% 65.30 45.8 19.41 3.93 2.20 15.30 15.61 14.90
Compaction Characteristics The West African Standard Compaction method was used for this research work. The maximum dry density (MDD) are 17.45 kN/m3, 16.45 kN/m3 and 16.3 kN/m3 and optimum moisture content (OMC) of 12.5%, 17.5%, and 14% for samples A, B, and C respectively at 0% stabilization (at the natural state). The MDD gradually decreased to 4% stabilization state while it suddenly increased at the 6% stabilization state for sample A as shown in Figure 2 below. MDD decreases non-uniformly for the remaining samples B and C. The corresponding optimum moisture contents are shown in Figure 3. Result shows increasing OMC and decreasing MDD as the percentages of cement content and bamboo leaf ash admixture increased, for all the tests carried out for the three samples.
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Bello, Afeez Adefemi; Ige, J. A., Ibitoye, Grace Ibironke 18 Sample A Sample B
Maximum dry density (kN/m3)
17.5
Sample C
17
16.5
16
15.5
15 0
1
2
3
4
5
6
7
8
9
% stabilizer - Cement & Bamboo Leaf Ash
Fig. 2: Variation of the MDD with the % Increase in Stabilizers (Samples A, B & C) 20 Sample A 19
Sample B Sample C
Optimum moisture content (%)
18 17 16 15 14 13 12 11 10 0
1
2
3
4
5
6
7
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% Stabilizer- Cement & Bamboo Leaf Ash
Fig. 3: Variation of the OMC with the % Increase in Stabilizers (Samples A, B & C)
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California Bearing Ratio Unsoaked CBR method was used for this test. The values of the California Bearing Ratio shown in Fig. 4 are 20.88, 10.34 and 10.33 for the soil sample A, B, and C respectively. The CBR percentage increases to 23.24 (at 8% cement -BLA), 19.95 (at 8% cement -BLA) and 14.89% (at 6% cement-BLA) for samples A, B and C respectively. There is no significant influence of the stabilizer on the soil samples used, hence the need for further research on the samples required. 25
Carlifornia bearing ratio (%)
20
15 Sample A Sample B Sample C 10
5
0 0
1
2
3
4
5
6
7
8
9
% Stabilizer - Cement & Bamboo leaf ash
Fig. 4: Variation of the CBR with the % Increase in Stabilizers (Samples A, B & C)
Conclusion The result of the grain size analysis shows that sample A belongs to the group A–7–6, sample B, A–7–6, and sample C, A–7–5 according to the AASHTO classification system, While samples A, B, and C are classified as gravelly silt, high plasticity silt, and lean clay respectively, hence the need for stabilization. The West African Standard Compaction method was used for this research work. The maximum dry density (MDD) are 17.45 kN/m3, 16.45 kN/m3 and 16.3 kN/m3 and optimum moisture content (OMC) of 12.5%, 17.5%, and 14% for samples A, B, and C respectively at 0% stabilization (at the natural state). The MDD gradually decreased to 4% stabilization state while it suddenly increased at the 6% stabilization state. MDD decreases non-uniformly for the remaining samples B and C. Result shows increasing OMC and decreasing MDD as the percentages of cement content and bamboo leaf ash
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admixture increased, for all the tests carried out for the three samples. This was due to the agglomeration of large particles (sand and gravel) occupying larger space with a corresponding drop in dry density and because of extra water required for the hydration of cement and the pozzolanic reaction of bamboo leaf ash and respectively. The values of the California Bearing Ratio increase slightly from 20.88, 10.34 and 10.33 to 23.24 (at 8% cement-BLA), 19.95 (at 8% cement-BLA) and 14.89% (at 6% cement-BLA) for samples A, B and C respectively. There is no significant influence of the stabilizer on the soil samples used, hence the need for further research on the samples required.
References [1] Akintola, F. A. (1982). ‘Geology and Geomorphology.’ In: Nigeria in Maps. R.M Barbour, Editor, Hodder and Stoughton, London. [2] Areola, O. (1982). ‘Soils’. In: Nigeria in Maps, R. M, Barbour, Editor Hodder and Stoughton, London U. K. [3] Bello, A. A. (2011) ‘Influence of Compaction Delay on CBR and UCS of Cement Stabilized Lateritic Soil’ Pacific Journal of Science and Technology, USA, 12(2):87-98. [4] Bello, A. A. and Adegoke, C. W. (2013) ‘Geotechnical Characterization of Abandoned Dumpsite Soil, ARPN Journal of Earth Sciences, ISSN 2505-403X, Asian Research Publishing Network, 2(3): 90 -100 [5] Berthelot C., Marjerison B., Gorlick R., Podborochynski R., Fair J. & Stuber, E. (2009). Field investigation of granular base rehabilitation project incorporating a woven geotextile separation layer, sand, and cement stabilization, Canadian Journal of Civil Engineering, 36(1): 14–25 [6] Chndra, S. (1987). “Stabilization of Clayey Soils with Lime, Cement and Chemical Additives Mixing”, In: Josh, R.C. and Griffihs, F.J. (Eds), Prediction and Performance in Geotechnical Engineering pp. 177 – 181. A.A., Balkema, Rotterdam. [7] Gadzama, E. W. (2009). Evaluation of Soil Samples From Federal University ofTechnology, Yola Site, Nigerian Journal Of Engineering,15(2):80-88 [8] Garber, C. F. and Hoel, M. F. (2000). “Traffic and Highway Engineering”, Second Edition, London: Brooks/Cole Publishing Company, pp. 481-492, 927930. [9] Head, K. H. (1992). “Manual of Soil Laboratory Testing”, Volume 1: “Soil Classification and Compaction Tests”, Second Edition, Pentech Press, London. [10] Holtz, R.D. and Kovacs, W.D. (1981). “An Introduction to Geotechnical Engineering”, Prentice Hall. [11] Ola, S. A. (1975). Stabilization of Nigerian Laterite soils with cement, bitumen and lime. Proceedings of the sixth Regional conference for Africa on Soil Mechanics and Foundation Engineering, Durban. 1:145-152.
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[12] Ola, S. A. (1983). Geotechnical properties and behaviour of some Nigerian lateritic soils.in S.A.Ola (1983), Tropical Soils of Nigeria in Engineering Practice, A.A. Balkema. Rotterdam, pp 61-84. [13] Olugbenga, O. A. and Akinwole, A. A. (2010). “Characteristics of Bamboo Leaf Ash Stabilization on Lateritic Soils in Highway Construction”, An International Journal of Engineering and Technology 2(4):212 – 219. [14] Osula, D. O. A. (1989). Evaluation of Admixture stabilization for problem laterite. Journal of Transportation Engineering, 115(6):674-687 [15] Thagesen, K. P. (1989). “Foundation Engineering”, Second Edition. New York: Wiley, 1989.
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