Nigerian Journal of Engineering Science and Technology Research

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Due to excessive shrinkage and swelling characteristics, black cotton soils (BCS) pose a serious challenge to engineering structures founded on/in them. Soil stabilisation using cementitious or pozzolanic materials is usually a common practice of improving the engineering properties of the soil. In this study, the potential of Bauhinia thonningii fruit ash (BTFA) for stabilization of BCS was investigated. The BTFA used was obtained by controlled burning of Bauhinia thonningii fruit in an incinerator at a temperature of 6000C for 45min. After cooling and sieving through 75┬Ám standard sieve; chemical composition analysis of the ash was conducted using (XRF) procedures. Laboratory tests were conducted in accordance with BS 1924 (1990) on black cotton soil treated with 0%, 2%, 4%, 6%, 8%, 10% and 12% BTFA. The soil was classified as A-7-5(17) and CH according to the American Association of State Highway and Transport Officials and the Unified Soil Classification System. British Standard Light (BSL) and British Standard Heavy (BSH) compactive efforts were used. Samples were cured for 7, 14, and 28 days to determine the unconfined compressive strength (UCS), California bearing ratio (CBR), and compaction characteristics. Improvement on the engineering properties of BCS with varying degree was observed. Plasticity index, liquid limit, and optimum moisture content decreased with an increase in BTFA content while plastic limit and maximum dry density (MDD) increased with increasing BTFA content. The maximum UCS values attained at 28 days curing period were 242kN/m2 with BSL at 6% and 698kN/m2 with BSH at 10% BTFA contents respectively. Thus, the results satisfied the sub-base requirements by the Nigerian Federal Ministry of Works. The Nigerian General Specification of 30% CBR criterion for sub-base was not achieved with BTFA content of 10%. Based on these observations, BCS treated with BTFA could be recommended as a sub-grade material in road construction with 10% content being the optimum. For general stabilisation for sub-base and base courses, a mixture of BTFA and cement or lime might be required.

Authors : U.H. Rawayau1, A.Y. Abdulfatah and R.B. Shuaibu

Category : Open Access     Volume (Issue) : 5(1)     Date Uploaded : 22nd July 2019

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