Geomechanical behaviour of a soft soil stabilised with alkali-activated blast-furnace slags

Abstract

The use of industrial by-products in the context of soil stabilisation has recently been explored as a mean to substitute the massive use of ordinary Portland cement (OPC), whose production has severe environmental impacts. Therefore, the purpose of the present investigation was to assess the geomechanical behaviour of a soft soil stabilised with a sustainable alkaline binder incorporating ground granulated blastfurnaces slags (GGBS), a residue from the iron industry, activated with NaOH at short (28 days) – and long (90 days) term. The mechanical characterisation included the performance of oedometer and triaxial testing, where the impact of both, initial mean effective stress (p’0) and overconsolidation ratio (OCR) effects, was analysed on the stress-strain and volumetric strain curves, stiffness degradation and, triaxial failure surfaces of the specimens. Also, SEM-EDS, XRD and leachate analyses were also carried out at both curing ages. The mechanical results showed a significant increase of the shear strength and stiffness, and a stress-strain behaviour typical of artificially cemented soils with OPC. The detection of Si, Ca and Al suggests the formation of C-A-S-H, which explain the more pronounced development of strength and stiffness up to 28 days. No risk of soil contamination was detected due to the addition of activated GGBS to the soil.