Evaluation of Consistency Limits and Compaction Properties of Lateritic Soil-Rock Flour Mixtures to be used as Road Pavement Subgrade

Abstract

The study reported in this paper evaluated the consistency limits and compaction properties of lateritic soil stabilized with 0, 3, 6, 9 and 12% rock flour by dry weight of soil and compacted using British Standard Light (BSL), West Africa Standard (WAS) and British Standard Heavy (BHS) compactive efforts. Results show that the lateritic soil sample used for this study is classified as A-7-6 according to American Association of State Highway and Transportation Officials (AASHTO). The formulated mixtures from the A-7-6 soil and rock flour show an improvement in the index properties of the mixtures with increasing rock flour. The Liquid limit and Plasticity index reduced from 42 - 32% and 29.30 - 13.48% respectively as rock flour increased from 0 – 12%, while plasticity index of A-7-6 soil with rock flour shows considerable reduction in plasticity indices of mixtures with increasing content rock flour content. 1.802, 1.820 and 1.870g/cm³ were obtained as MDD values and 12.40, 11.90 and 11.60% as OMC values for the natural soil using BSL, WAS and BSH compaction efforts respectively. Also, at 12% of rock flour content, the MDD increased to 1.85, 1.870 and 2.010g/cm³ while the OMC increased to 14.80, 14.40 and 13.90% using the same compaction efforts. Based on results obtained, MDD result shows a progressive increase with higher rock flour content as well as higher compaction effort. The increase in MDD values suggest that the increase in rock flour content has positive influence on the strength and density of tested mixtures. In terms of consistency limits, the mixtures did not achieve the required threshold values for subgrade specified as LL < 35 and PI < 12% in local codes suggesting the use of higher rock flour contents to enhance these parameters. To optimize their structural strength for subgrade application, the mixtures should be compacted to 100% of the MDDs.