Enhancing durability of quarry fines modified black cotton soil subgrade with cement kiln dust stabilization

For soil materials to be effective as pavement subgrades, satisfying the durability conditions is essential especially in tropical latitudes where wet and dry climatic conditions prevail. This study investigated the use of cement kiln dust (CKD) to enhance the durability of black cotton soil (BC soil) subgrade modified with quarry fines (QF). Durability was assessed by California bearing ratio (CBR) swell and loss of strength upon immersion tests carried out on soil mixtures prepared with BC soil mixed with constant dosage of 10% QF and five levels of CKD concentration (0%, 4%, 8%, 12% and 16% by dry weight of soil). Specimens were compacted using British standard light (BSL) effort under optimum moisture condition, cured and then subjected to prolonged soaking. Test results show that mixtures containing 0% and 4% CKD failed the CBR and associated swell limits as well as the resistance to loss of strength criterion while both tests deemed soil mixtures containing 8–16% CKD durable. Moisture content evaluation revealed that inclusion of CKD reduced the moisture susceptibility of mixtures. Overall, the testing programme produced data showing that mixtures with CKD admixture have significant durability when exposed to prolonged saturation.