Low-carbon wet-ground fly ash geopolymer activated by single calcium carbide slag

Abstract

• Preparation of calcium carbide slag-activated wet-ground fly ash based eco-friendly geopolymers. • The wet grinding process is helpful for the refinement and pre-depolymerization of fly ash. • Growth rate of compressive strength of wet-ground FA geopolymer is increased up to 319.5%. • Mechanical activation synergizes with alkali activation synergistic enhance the pozzolanic activity of fly ash. • Wet-grinding FA optimizes the microstructure of the geopolymer and deepens the degree of reaction. Geopolymers are generally formed from silicon-alumina-based industrial wastes in a strongly alkaline environment. However, there is a contradiction between the high cost of strong alkali activators and the poor effect of calcium-based activators for geopolymers. In this study, low-cost calcium-based fly ash (FA) geopolymers were co-prepared using an industrial by-product, calcium carbide slag (CS), as an alkaline activator and a wet grinding process to pre-depolymerize the fly ash. The effects of CS dosing and wet grinding treatment on the mechanical properties, hydration, and microstructure of FA-based geopolymers were systematically characterized by using X-ray diffraction analysis, thermogravimetric analysis, and mercury porosimeter, solid-state NMR and mechanical property tests. The result indicated that the potential pozzolanic reaction was significantly higher for wet-ground fly ash (WFA) compared to raw fly ash (RFA), and the reaction with CS was more adequate, resulting in denser hydration products and refinement of the pore structure of FA based geopolymers, and their compressive strengths at 1 and 28 days were significantly higher than those of previous similar studies.