Cementitious characteristics and environmental behaviour of vitrified MSW incineration fly ash slag

Abstract

Although vitrification of municipal solid waste incineration fly ash (MSWIFA) is an energy-intensive process, it is a highly effective method to achieve detoxification and produce a vitrified MSWIFA slag (VFAS). This study presents cementitious characteristics and environmental behaviour of VFAS as a partial ordinary Portland cement (OPC) replacement in mortars. The hydration behaviour, mechanical properties, heavy metals leaching and environmental impacts of the produced mortars were evaluated. The experimental results showed that the leaching levels of lead (Pb) and chloride in VFAS were significantly lower than those of the original MSWIFA, and it can be considered as a non hazardous material. Regarding hydration behaviour, the replacement of 30% OPC by VFAS can accelerate early cement hydration, however obtaina relatively low cumulative heat of hydration. It took a long time to achieve a comparable OPC mortar strength at high VFAS replacement levels. Thus, VFAS can be regarded as a type of slowly reactive supplementary cementitious material (SCM). Moreover, using VFAS in mortars yielded a decrease in the global warming potential and non-renewable energy by an environmental impact assessment. This implies that using VFAS as SCM in cement based materials would be more sustainable for achieving carbon neutrality.