Improved understanding of the pozzolanic behaviour of MSWI fly ash with Ca(OH)2 solution
The study aims at investigating pozzolanic behaviour of MSWI fly ash in a saturated Ca(OH)2 solution at various times. The raw and water–washed fly ashes were selected for the pozzolanic solidification experiment to which mass ratios of the solution to ash (ml/g) were adjusted to be 3 and 10, whereas the solidification times were set from 7 to 28 days and from one to three months. From the XRD Rietveld analysis, a mineral assemblage of fly ash exhibited pozzolanic reactivity to form compounds of hydraulic cementitious materials. Here the considerable amounts of syngenite and gypsum, but small amounts of ettringite, hydrocalumite and C–S–H phase, were produced during the pozzolanic reaction of raw fly ash. Likewise, the washed fly ash exhibited the cementitious property with high quantity of gypsum and ettringite. From the leaching test, the solidified products exhibited release of lesser heavy metals about the untreated parent materials.
Keywords: pozzolanic solidification, MSWI fly ash, cementitious materials, Rietveld analysis, mineralogical analysis, municipal solid waste, MSW incineration, calcium hydroxide, Ca(OH)2, syngenite, gypsum, ettringite, hydrocalumite, leaching test