Mechanical properties and strengthening mechanism of silty sands stabilized with steel slag-based geopolymer binder

Abstract

Geopolymer binder has the advantages of early strength, fast solidification, high volume stability, and low permeability. It is beneficial to improve the mechanical performance of silty sands, saving cement consumption and being environmentally friendly. However, the strength improvement of silty sand stabilized with steel slag-based geopolymer was significantly controlled by their material composition and technical parameters. This study conducted a series of unconfined compression tests to investigate the material composition of steel slag-based geopolymer binders and their reasonable mixing ratio for silty sand stabilization. The optimum mixing ratio of precursor (steel slag) to alkaline activator (the combination of Na2SiO3 and CaO) and the optimum dosage of steel slag-based geopolymer for silty sand stabilization were explored. The strengthening mechanism of geopolymer-stabilized silty sands was discussed based on microstructural images and elemental concentrations of primary components observed by SEM and EDS. The results show that when the mass ratio of steel slag : Na2SiO3 : CaO was 80:35:21, and the steel slag-based geopolymer material was 15%, the silty sand could achieve the best mechanical performance improvement. The microstructural characteristics of geopolymer-stabilized silty sands at different curing ages illustrated that the compactness and integrity of silty sand structures were enhanced over the curing age. The improving cementitious contact among particles and enlarging particle size was responsible for the strength improvement of silty sand. This research can provide a reference for applying steel slag-based geopolymer in silty sand stabilization in engineering practices.

Keywords

• silty sand
• mechanical properties
• strengthening mechanism
• microstructure characteristics
• geopolymer binder