Geo-mechanical behavior of clay soils stabilized at ambient temperature with fly-ash geopolymer-incorporated granulated slag

Abstract

Geopolymer is a cementitious material that can replace ordinary Portland cement in several geotechnical engineering applications, such as soil stabilization, with the advantages of much lower harmful emissions and energy consumption. This paper presents a rigorous evaluation of the geo-mechanical behavior of different types of clay soils treated with geopolymer, including the influence of soil characteristics and mineralogy. Two natural clay soils in addition to a commercially available kaolin clay were used for this investigation. Laboratory experiments were performed including unconfined compressive strength (UCS) and consolidated undrained (CU) triaxial compression tests under different confining pressures. The UCS and triaxial tests indicated that the addition of geopolymer considerably increased the yield stress and initial stiffness of all examined clays. With the increase of geopolymer content, the stress–strain behavior of treated clays was found to develop progressively from ductile response into a post-peak brittle fashion. The CU tests also demonstrated that the addition of geopolymer changed the initial characteristics of remolded clays from quasi-over-consolidated to heavily over-consolidated, rendering high yield surface and more effective shear strength parameters (i.e., cohesion and friction angle). Moreover, although the overall qualitative stress–strain and stress path responses of the clays were similar, significant quantitative differences were observed, particularly in terms of the attainable yield strength, stiffness, and shear strength. These differences can be attributed mainly to the heterogeneity associated with the soil mineralogy and the corresponding differences in the interaction between the clay/non-clay minerals and geopolymer.