Influence of Delay after Mixing on Compaction Characteristics of Cement- Locust Bean Waste Ash Modified Lateritic Soil

Abstract

A lateritic soil modified with up to 4% of ordinary Portland cement (OPC) and up to 8% of locust bean waste ash (LBWA) by dry  weight of soil was evaluated for use in road construction. Lateritic soil – OPC - LBWA mixtures were delayed for up to 3 hours aftermixing before compaction at British Standard light (BSL) energy, thus simulating the likely delay in the placement of the mixtures that might occur in the field. Results obtained show that maximum dry density (MDD) values of the natural soil increased from 1.62 to 1.79Mg/m³ at 3 hours delay after mixing when treated with 4% OPC/6% LBWA, while the optimum moisture content (OMC) values decreased from 16.2 to a minimum of 11.33% after 3 hours when the soil was treated with 2% OPC/4% LBWA blend. Statistical analysis was carried out on results obtained using analysis of variance (ANOVA) with the Microsoft Excel Analysis Tool Pak Software Package to determine the levels of significance of effect of cement/ and LBWA on the properties of the soil. The effects of cement and LBWA from the results obtained were not statistically significant on the compaction characteristics. Based on the results obtained from the study, it is recommended that an optimal mix of 2% OPC/6% LBWA be used for the modification of lateritic soil and should not be placed more than 2 hours after mixing for the construction of sub-base and base of lightly trafficked roads. ^©University of Ibadan

Keywords: Compaction, Delay, Lateritic soils, Locust bean waste ash