Laboratory and Statistical Evaluation of Cement and Lime on the Properties of Tropical Black Clay – Iron Ore Tailings Mixtures

The need for cheaper and more economical soil improvement methods is of great significance in order to reduce the construction cost of flexible pavements. Also, major problems caused by industrial waste in Nigeria can be minimised by recycling or re-using of such wastes for soil improvement. The application of cement and lime along for such purpose has proven to increase the construction cost. Thus the use of industrial waste such as iron ore tailings (IOT) could aid in reducing the construction cost. Series of laboratory and statistical investigations were performed to compare the effect of cement and lime on the properties of tropical black clay (i.e. black cotton soil, BCS). Soil samples were admixed with up to 10 % IOT content and modified with up to 4 % each of cement and lime by dry weight of soil to evaluate their plasticity and compaction characteristics. Compaction was done with British Standard light (BSL) energy. Statistical tests for regression and correlation was achieved using Mini-tab R15 and Microsoft Excel software correspondingly. Results disclosed decreased in liquid limit and plastic limit. Liquid limit values of 56, 54.8, 54.5, 52.5, 52 and 51% were noted for 0, 2, 4, 6, 8 and 10% IOT content. Similar trend was noted for 1, 2, 3 and 4% lime and cement concentrations. A rise in maximum dry density (MDD) and drop in optimum moisture content (OMC) with greater concentration of IOT for all the lime and cement contents under study was noted. Statistical analysis revealed that soil-lime-IOT mixtures gave higher predicted values than soil-cement-IOT mixture for determining plasticity and compaction characteristics of BCS – IOT mixtures. Thus, 4 % lime – 6 % IOT mixture met the criteria for flexible pavement purpose as proposed by Nigerian General Specifications and is recommended for used as pavement material for roads that are lightly trafficked. While the soil – cement - IOT mixes fell to meet the criteria for used as pavement material.