Cement modification of tropical black clay using iron ore tailings as admixture

The effect of iron ore tailings (IOT) on cement modified tropical black clay was studied. The natural soil was treated with up to 4% cement and 10% IOT by dry weight of soil. Specimens of treated soil compacted with British Standard light, BSL or standard Proctor (relative compaction = 100%) were subjected to index, sieve analysis, compaction, and shear strength parameters tests. The results of laboratory tests show that properties of the modified soil improved when treated with cement–IOT blends. Test results show a decrease of the fine fraction, decrease in liquid and plastic limits, and an increase in maximum dry density (MDD), with a decrease in optimum moisture content (OMC) as well as a decrease in shear strength value of the natural soil up to 6% IOT content. Microanalysis of the natural and optimally (4% cement/6% IOT) modified soil using scanning electron microscope (SEM) showed a change in the fabric orientation of the soil particles. Although the engineering properties of the soil was improved, the modified soil did not meet the requirements of the Nigerian General Specifications of not more than 35% passing sieve No. 200, maximum plasticity (PI) index of 30% and liquid limit (LL) of a maximum of 50% when used as a sub grade material in road construction. However, an optimal blend of 4% cement/6% IOT improved its workability with increase in curing period.