Experimental and Statistical Study on Black Cotton Soil Modified with Cement–Iron Ore Tailings

Abstract

The investigation focused on the response of black cotton soil (BCS) treated with mixtures of iron ore tailings (IOT) and cement to varying compaction effort (CE). Preliminary tests showed that the un-treated soil is A-7-6 (22) on the basis of AASHTO protocols of classification while the USCS (Unified Soil Classification System) guidelines placed the soil in CH group. Laboratory tests carried out included cation exchange capacity, CEC, Specific gravity (Gs) and compaction test. Three compaction energy levels (i.e., British Standard heavy (BSH), West African Standard (WAS) and British Standard light (BSL)) were adopted for the compaction test. Test results showed that CEC decreased; Gs and MDD increased while OMC also decreased for all cement contents considered when admixed with the different IOT contents up to 10 % IOT by the soil dry weight. MDD values of 1.58, 1.59, 1.62, 1.64, 1.64 and 1.66 Mg/m3 were noted for 1% cement and 0, 2, 4, 6, 8 and 10% IOT content compacted with BSL energy. Also, OMC values of 21.2, 20.8, 20.5, 20, 20.3 and 20.2% were noted for 1% cement and 0, 2, 4, 6, 8 and 10% IOT content compacted with BSL energy. Same trend was noted for higher cement concentrations and compactive efforts. Regression models for MDD and OMC, considered as dependent variables while C (cement content), CE, IOT, Gs and PF (percentage of fine) as independent variables were developed using software (Mini-tab R15). The result of regression analysis shows that the independent variables considered greatly influence the dependent variables. ANOVA (Analysis of variance) was use to establish the levels of contributions of cement and IOT to the improvements recorded. Therefore, black cotton soil optimally treated with 4% cement 10% IOT blend and compacted with BSH energy is recommended for soil remediation or geotechnical engineering applications. Keywords— Compaction effort, iron ore tailings, black cotton soil (BCS), Analysis of Variance, regression analysis.