Comparison between the Strength Characteristics of Pozzolan Stabilized Lateritic Soil of Coconut Shell Husk Ash and Palm Kernel Shell Husk Ash Admixtures
Citation: ”Comparison between the Strength Characteristics of Pozzolan Stabilized Lateritic Soil of Coconut Shell Husk Ash and Palm Kernel Shell Husk Ash Admixtures, American Research Journal of Civil and Structural Engineering, vol 1, no. 1, pp. 36-46.
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The discharge of agricultural, industrial and domestic wastes is at increasing rate on daily basis in the developing countries. These wastes are generated in enormous quantity and improper waste management systems and lack of proper monitoring system leads to these wastes constituting nuisance to the environment. Converting these wastes to useful and economical additives for construction work is the aim of this study. This study analyses the results of the comparison between the strength characteristics of pozzolan stabilized lateritic soil using coconut shell husk ash (CSHA) and palm kernel shell husk ash (PKSHA) as admixtures. OMC, MDD, Particle Size Distribution, California Bearing Ratio, Triaxial Test, Unconfined Compressive Strength and Atterberg limit were investigated. The soil is a clayey soil classified as A-7-6(20) according to AASHTO and CH inorganic sandy fat clay according to Unified Classification System. CBR value of the unsoaked was greater than the soaked and it increased at different percentages of CSHA and PKSHA, at control CBR value for soaked and unsoaked at 2.5 and 5.5 penetrations were 4.0/6.0 and 3.0/6.0 KN respectively. At 10% CSHA, the CBR value improved to 13.0 KN and 9.0KN for unsoaked and soaked at 2.5mm at 5.0mm, while 10% PKSHA improved to 14.0 KN and 10 KN unsoaked and soaked at 2.5mm and 5.0mm respectively. Addition of CSHA and PKSHA increased optimum moisture content and decreased maximum dry density. UCS increased with respect to the curing days and different percentages of CSHA and PKSHA. At control, UCS was 6.43, 8.65 and 14.80 KN/m2 for 0, 7 and 14days curing. It improved to 10.79, 31.82, 40.00 KN/ m2 at 10% CSHA and 11.38, 33.43 and 41.64 KN/m2 at 10%PKSHA for 0, 7 and 14days curing respectively. PI and LL reduced and PL increased as percentages of CSHA and PKSHA increased. Coconut shell husk ash and palm kernel shell husk ash are good addictives for soil stabilization as they increased and improved the strength characteristics of the soil.
Keywords: Pozzolan, strength characteristics, stabilized lateritic soil, coconut shell husk ash, palm kernel shell husk ash.
Soil stabilization refers to the procedure in which a special soil, a cementing material, or other chemical or non chemical materials are added to a natural soil or a technique used on a natural soil to improve its geotechnical properties, (Abood et al, 2007; Salahudeen and Ochepo, 2015). Soil stabilization techniques for road construction are used in most part of the world although circumstance and reasons for resorting to stabilization vary considerably. Nearly every road construction project will utilize stabilization techniques. When used, these stabilizing agents can improve and maintain soil moisture content, increase soil particle cohesion and serve as cementing and water proofing agents, (Janathan, 2004). Soil stabilization has widely been recommended for developing countries for various elements of their pavements. The reasons usually are that the use of local conditions is of paramount importance while developing any soil stabilization technique. This is because a country’s climatic conditions can affect the behaviour of stabilized soil materials as well as construction procedures. Soil stabilization can improve the shear strength of the soil and control shrinkage swell properties of the soil thus improving the load bearing capacity of foundation soils (Brenema, 2010). Laterite is a Reddish residual soil from rocks. Soils are mostly used for construction of road bases in Nigeria. Laterite is high in iron oxide and aluminium hydroxide content, but low in silica content (Kowalski et al, 2007). Lateritic soils are residual soils and are mainly found in the tropical and sub-tropical regions. These are soils formed by the leaching of lighter minerals like silica. Consequently, it is the enrichment of the heavier minerals like iron and aluminium oxides (sesquioxides). It was stated that the degree of laterization is estimated by silicasesquioxide ratio (Makasa, 2004). Researches all over the world today are focusing on ways of utilizing, either industrial or agricultural wastes as a source of raw materials for the industry. These wastes utilization would not only be economical, but may also result to foreign exchange earnings and environmental pollution control (Bienia et al, 2006). In this research study, coconut shell husk and palm kernel shell husk wastes were considered as admixture. The disparity between countries with excellent roads and highway networks and those with poor ones can be expected to increase. This gap will be due to primary differences in the funding base resulting from socioeconomic and geopolitical conditions. At the same time, regions throughout the world share a common need to maintain and rebuild aging transportation system infrastructure. Yet if past policies prevail, money will be used primarily to build new facilities, with a smaller share of funds being allocated to maintaining and rebuilding existing facilities (Amoanyi, 2012; Breneman, 2009). The world already has many miles of unpaved and marginally paved roads. In many areas worldwide, new roads will be unpaved as well. In places where roads are paved, they will be replaced or repaired from the ground up. Because of aging, broken-down pavements may require recycling and rebuilding but more likely they are the result of poor support conditions combined with higher traffic loads. New roads, both paved and unpaved will probably be placed in locations where there were no roads before because of less ideal sub grade conditions. In all of these situations, less-than-desirable materials are likely to be used. Use of these materials will in turn require the application of stabilization techniques presently available, as well as those likely to evolve in the next century (Aigbodio et al, 2010). Hence in the new millennium, we will face the challenge of developing better chemical stabilizers and mechanical stabilization techniques; new, quicker, and better testing methods; and better and environmentally safe methods for using waste materials for highway construction. Research is needed in a number of areas to develop the materials and methods required to meet this challenge. The primary aim of this study is the comparison of the strength characteristics of pozzolan stabilized lateritic soil with coconut shell husk ash and palm kernel shell husk ash. Specifically, the objectives of the study were; (i) to determine the effect of palm kernel shell husk ash on pozzolan stabilized lateritic soil, (ii) to determine the effect of coconut shell husk ash on pozzolan stabilized lateritic soil and (iii) to compare the effects of coconut shell husk ash and palm kernel shell husk ash on the geotechnical properties of pozzolan stabilized Oboro lateritic soil.
MATERIALS AND METHODS
Lateritic Soil Sample
The lateritic soil sample used for this research work was collected from a borrow pit located at Umuigu of Oboro in Ikwuano Local Government Area of Abia State. They were all collected at depths representative of the soil stratum and not less than the 1.2m below the natural ground level. These were kept safe and dry in bags and were later air dried in pans fo r t wo we e ks to allow partial elimination of natural moisture which may affect analysis.
The pozzolan soil sample used for this research work was collected from ohyia near mechanical village Enugu Port-Harcourt expressway, in Umuahia South Local Government Area of Abia State. The sample was collected in a bag and it was air dried for two weeks to eliminate the moisture in it. It was then crushed to powder form using core cutter with bulk density mould.
Palm Kernel Shell Husk
The palm kernel shell husk was obtained from oil palm mill in Edem Inyang village in Ukanafun Local Government Area of Akwa Ibom State. The palm kernel shell husks were burnt in a no soil surface and it was sieved properly to obtain a finer particle passing sieve no. 200.
Coconut Shell Husk
The coconut shell husk used for this research was collected at Edem Ekpat Village in Etinan Local Government Area of Akwa Ibom State, Amaoba and Umudike villages in Ikwuano Local Government Area of Abia State. The coconut shell husk were burnt in a no soil surface, it was properly sieved to obtain a finer particle passing sieve no. 200.
Particle size distribution tests were performed on the pozzolan stabilized lateritic soil sample using standard sieves in line with British Standard methods (BS 1377–1990: Part 2),
Atterberg Limits Tests
Using the pozzolan stabilized lateritic soil sample retained on the 4.25mm sieve the Atterberg limits tests, comprising liquid limit (LL) and plastic limit (PL), were determined and the plasticity index (PI) was calculated in accordance with BS1377 1990: Part 2. The tests were carried out on the pozzolan stabilized soil and then on the soils with different proportions of coconut shell husk ash and palm kernel shell husk ash additive of 2.0%, 4.0%, 6.0%, 8.0% and 10.0% by mass of soil sample.
Proctor standard compaction tests to determine the maximum dry density (MDD) and the optimum moisture content (OMC) of the pozzolan stabilized lateritic soil were in accordance with (BS1377–1990: Part 4).The tests were carried out on the pozzolan stabilized soil and then on the soils with different proportions of coconut shell husk ash and palm kernel shell husk ash additive of 2.0%, 4.0%, 6.0%, 8.0% and 10.0% by mass of soil sample.
California Bearing Ratio Test
The California Bearing Ratio tests were conducted on pozzolan stabilized soil samples which have been compacted with 2.5kg rammer. The tests forces on a plunger at penetration of 2.5mm and 5.0 mm were determined and the California Bearing Ratio (CBR) was calculated as specified (BS1377–1990: Part 4). The tests were carried out on the pozzolan stabilized soil and then on the soils with different proportions of coconut shell husk ash and palm kernel shell husk ash additive of 2.0%, 4.0%, 6.0%, 8.0% and 10.0% by mass of soil sample.
Specific Gravity Test
Specific gravity tests were performed on the pozzolan stabilized lateritic soil sample using pycnometer in line with British Standard methods (BS 1377–1990: Part 2).
Unconfined Compressive Strength Test and Triaxial Test
The measurement of the effective shear strength parameters for cylindrical specimens of saturated soil which have been subjected to isotropic consolidation and then sheared in compression, under a constant confining pressure, by increasing the axial strain was studied. The test was performed unconsolidated under undrained conditions, with the possibility of measuring pore pressure and volume change. The test was carried out in accordance with (BS1377–1990: Part 8).
RESULTS AND DISCUSSION
Laboratory Study Results and Data
The chemical composition of coconut shell husk ash and palm kernel shell husk ash according to (Johnson et al, 2012) and (Otunyo et al, 2010) are shown on Tables 1 and 2 respectively.
The results of the Atterberg limit examination of the natural oboro lateritic soil and the studied effect of varied proportions of the CSHA and PKSHA are shown in Figure 2 and Table 4 and Figure 3.