SEM and XRD investigations on lithomargic clay stabilized using granulated blast furnace slag and cement

Abstract

Lithomargic clay soil is found along the western coast of southern India extending from Cochin to Goa below hard lateritic soil varying in large depths. This soil is problematic as it loses its strength upon saturation and is mainly consisting of silt size particles. Granulated blast furnace slag is a by-product from the iron industry available in large quantities. Since it has high percentage of CaO (i.e. 30–45%), it has latent hydraulic properties. Laboratory experiments were conducted to improve the strength properties of lithomargic clay by replacing soil with varying percentages of GBFS. Lithomargic clay stabilised with 25% GBFS was found to be the optimum. Further addition of 2 and 4% cement to the optimised slag–soil mix improves the strength properties significantly. SEM and XRD analyses were carried out to observe the microstructural changes in the stabilised soil. The reason for the improvement in strength was established through SEM and XRD. C-S-H, C-A-S-H and few other similar compounds were responsible in improving the strength properties by filling the voids between the soil particles. From the quantitative EDS analysis, it was concluded that the strength improvement was due to the increase in Ca:Si ratio and decrease in Al:Ca ratio.