Characterization and evaluation of cement-based systems containing solution-treated municipal solid-waste incineration fly ash

Abstract

This study aims to explore the potential utilization of the fly ash produced from co-burning municipal solid waste (MSW) and natural gas in cement-based materials. The as-received MSW incineration (MSWI) fly ash was washed with water and a sodium hydroxide (NaOH) solution. The untreated and treated fly ashes were characterized for their chemical compositions, crystalline mineral phases, and surface morphologies, and they were then used to replace cement at 0%, 10%, 20%, and 30% (by weight of binder) in a mortar (w/b = 0.45). The engineering properties of the resulting mortar, including flowability, setting time, isothermal calorimetry, foam capacity and stability, compressive strength, free-drying shrinkage, and bulk electrical resistivity, were also assessed. The results showed that the water and NaOH solution treatments substantially reduced the amounts of alkaline (by 96% and 74%, respectively) and chloride salts (by 96% and 95%, respectively) in the untreated fly ash. Mortars containing 10% and 20% water treated fly ash, or 10% NaOH-solution treated fly ash exhibited comparable or improved flowability, foaming behavior, compressive strength, drying shrinkage, and bulk electrical resistivity when compared with the mortar without MSWI fly ash. These results suggest that simple water and NaOH solution treatments can enable the successful application of MSWI fly ash in cement-based materials.