Effect of curing time on strength development in black cotton soil - Quarry fines composite stabilized with cement kiln dust (CKD)

Combined treatment techniques have been adopted by many pavement designers and site engineers to improve the strength and stability of subgrades or foundation soils of expansive sites. In this regard, research was conducted to investigate the effect of curing time on strength development of black cotton soil (BC soil) stabilized with 10% quarry fines (QF) and varying percentages (0-16%) of cement kiln dust (CKD). Preliminary tests such as Atterberg limits, compaction parameter test together with a series of unconfined compression tests were conducted on soil mixtures. Specimens for unconfined compression tests were prepared at their respective optimum moistures, compacted using British standard light (BSL) compaction effort and tested at curing times of 7, 14, 21 and 28 days. Data from the study revealed that the curing duration exerted a significant influence on the stress-strain behavior of soil mixtures together with the strain at failure which decreased by about 30-50% as the curing time increased. Unconfined compressive strength data showed improved strength values ranging from 1.25 to 5.25 times higher than the value for specimens tested immediately after preparation. Data developed in this study are expected to be useful to pavement designers and site engineers in the field implementation of the stabilization scheme such as when to open the stabilized layer to construction traffic or when to proceed with further construction works.