Briefing: Lateritic soil and calcined kaolin for earth embankments

Compacted lateritic soil treated with calcined kaolin was considered as a potential material for construction works in this study. The tests carried out were consistency limit, compaction, unconfined compressive strength and shear strength tests. The calcined kaolin contents were 2·5, 5·0, 7·5, 10·0 and 12·5%, all measured by weight of the dry soil. The specimens of the soil mixtures were prepared using two compaction energy levels – namely, the British standard light (BSL) and West African standard (WAS) – at moulding water contents of −2, 0, +2, +4% of the optimum moisture content. The results showed that consistency limits and optimum moisture content reduced, while the maximum dry density rose with increase in calcined kaolin content. The compressive strength improved up to 97 and 115% for BSL and WAS, respectively, while shear strength increased by 137·80% with calcined kaolin content up to 12·5%. The compacted lateritic soil without treatment could not satisfy the compressive strength requirement for some earth embankments such as liners, but up to 5% treatment of calcined kaolin at the optimum moisture content was found suitable for BSL and WAS.