Sustainable municipal solid waste incineration fly ash (MSWIFA) alkali-activated materials in construction: Fabrication and performance

Introduction. Recent years have seen a pressing need to dispose of municipal solid waste due to rapid urbanization. The municipal solid waste incineration fly ash (MSWIFA) produced from solid waste incineration power plant exhibits pozzolanic properties and poses concern of toxicity leaching when used directly as building materials. This paper presents an alkali-activation method to produce sustainable alkali-activated MSWIFA materials (AAFMs) with various MSWIFA dosages and investigate the corresponding fabrication and performance. Materials and Methods. Composited alkali activators activate the MSWIFA with constant alkalinity of 5% and the molar ratio of Si/Na = 0.86. The resulting geopolymers' bulk densities, mineral composites, morphology, and compression strength are thoroughly examined. Results and discussions. Results show that the use of MSWIFA may lead to more loose structures because the bubbles are generated from metallic aluminum and alkali activators. Additionally, the production of multiple crystals also accounts for increasing porosity. The generated multi-crystals such as Sylvite, Halite, Hydrocalumite, Calcium Hydroxide, and Ettringite are further detected from the morphology and mineral analysis. Furthermore, compression tests and toxicity characteristic leaching procedures (TCLP) are conducted to investigate the mechanical performance and heavy metals solidification performance of AAFMs, with an optimal compression strength of 19.99MPa at 28 days for AAFM-10 while toxicity leaching is subject to regularity limits. Conclusions. This study shows that great potential of using the alkali-activation method to recycle hazardous municipal solid fly ash into construction materials with both ecological safety and high performance.