Innovative dual-benefit recycling and sustainable management of municipal solid waste incineration fly ash via ultra-high performance concrete

Abstract

Millions of tons of municipal solid waste incineration fly ash are generated worldwide each year. Currently, landfilling is the primary disposal method, consuming vast land resources and posing significant risks of soil and groundwater contamination due to the high concentration of hazardous heavy metals. Thus, this study investigated the potential of recycling hazardous municipal solid waste incineration fly ash into non-hazardous ultra-high performance concrete for sustainable development. The mechanisms of heavy metal solidification and binding were examined through Density Functional Theory calculations and microscale experiments. Heavy metals are solidified through the adsorption and binding effects of calcium silicate hydrate and the encapsulation effect of the compact accumulation within the concrete structure. The pore structure of the concrete and the chemical reactions between the fly ash and cement were analyzed to validate the heavy metal solidification mechanism. After solidification, the leaching concentrations of heavy metals from the concrete were two orders of magnitude lower than the limit specified by the Toxicity Characteristic Leaching Procedure. The autogenous shrinking of UHPC with MSWIFA was reduced by about 50 %, and the compressive strength of the concrete decreased. The incorporation of MSWIFA led to approximately a 20 % reduction in energy consumption and carbon emissions. The concrete with MSWIFA exhibited better overall performance. This study presents an innovative and effective approach for recycling municipal solid waste incineration fly ash into non-hazardous concrete, contributing to sustainable hazardous waste management and reducing environmental pollution caused by heavy metals.