Time-dependent strength and mineralogy of lime-GGBS treated naturally occurring acid sulfate soils treated naturally occurring acid sulfate soils

This study investigates the effect of time-dependent mineralogical changes on the unconfined compressive strength (UCS) behavior of lime–ground granulated blast furnace slag (GGBS) treated naturally occurring acid sulfate soils (ASS) containing various proportions of pyrite. Pyrite (0, 2, 4% by weight), GGBS (5, 10, 15, 20% by weight), a fixed lime content of 15% by weight and curing periods up to 365 days were investigated. Mineralogical control on the strength of treated ASS samples was investigated using UCS analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Quantitative phase analysis using XRD data and the Rietveld method was carried out to quantify mineralogical changes. Results show a decrease of UCS values after 180 days curing for ASS containing 4% by weight additional pyrite and treated with 20% by weight GGBS. XRD and SEM analyses suggest that a decline in the abundance of cementitious mineral phases coincides with possible formation of thaumasite-ettringite and the degradation of strength in treated ASS.