ABSTRACT
The study was aimed at the evaluation of the effect of iron ore tailings as an admixture in cement stabilization of lateritic soil. Air-dried soil was treated with ordinary Portland cement (OPC) - iron ore tailing (IOT) blend in stepped concentration of 0, 2, 4, 6 and 8 % by dry weight of soil for OPC and 0, 2, 4, 6, 8 and 10 % by dry weight of soil for IOT. The index properties tests carried out on the natural soil showed that the soil belongs to A-7-6(14) in the AASHTO classification system and CL according to the Unified Soil Classification System (USCS). Compaction characteristics of the natural and treated soil samples were determined using three energy levels, namely, British Standard light (BSL), West African Standard (WAS) and British Standard heavy (BSH). The effect of pozzolanic and particle inter-surface activities on the properties of specimens as well as the leaching potential of IOT were investigated through cation exchange capacity, microanalysis and batch equilibrium tests. Test results showed a decrease in cation exchange capacity with increase in IOT content. The liquid limit decreased from 44.7 % for the untreated soil to 38.5, 34.7 and 31.8 % at 4 % OPC/ 6 % IOT, 6 % OPC/ 6 % IOT and 8% OPC/ 8 % IOT treatments respectively, while the plastic limit increased from the 22.5 to 25.1 % at 6% OPC/ 6% IOT treatment. Unconfined compressive strength (UCS) values of 263.98, 565.37 and 875.46 kN/m2 obtained for the natural soil after 7 days of curing, increased to 2590.38, 3304.94 and 3504.6 kN/m2 at 4% OPC/ 6 % IOT treatment and 3783.64, 3860.97 and 3993.14 kN/m2 at 6 % OPC/6 % IOT treatment for specimens compacted using BSL, WAS and BSH energies, respectively. The treated specimens met the 1720 kN/m2 requirement for adequate cement stabilization. The California bearing ratio (CBR) results showed significant improvement of the natural soil with peak values of 100 %, 100 % and 100 % (Unsoaked) and 80 %, 80 % and 90 % (Soaked) at 6 % OPC/6 % IOT treatment for BSL, WAS and BSH compaction, respectively. viii Durability assessment showed that for BSL compaction specimens treated with 4 % OPC/6 % IOT and 6 % OPC/6 % IOT blend recorded 85 and 87 % resistance to loss in strength respectively, which was greater than the 80 % recommended for 7 days curing and 4 days soaking, although specimens were subjected to harsher condition of 7 days curing and 7 days soaking. Statistical analysis of the results using the two-way analysis of variance (ANOVA) show that OPC/IOT significantly improved the soil properties. Batch equilibrium test results show that the desorbed values of iron and pH of the optimal 6 % OPC / 6 % IOT blend fall within the permissible value recommended by the World Health Organisation (WHO) and Nigeria Industrial Standard (NIS). It is recommended that lateritic soil treated with 4 % OPC/ 6 % IOT blend can be used as a sub-base material in construction of medium trafficked road when compacted with a minimum BSL energy
