Analysis of the cement solidification effect and mechanisms of municipal solid waste incineration fly ash

The chemical and mineral composition, heavy metals content, heavy metals leaching amount of municipal solid waste incineration fly ash (MSWI Fly ash) are experimentally studied. The results show that the mineral and oxide constituents of MSWI fly ash are very similar to coal fly ash. There are many heavy metals in MSWI Fly ash including chromium, lead, copper, zinc, cadmium and mercury. The leaching concentrations of lead and chromium exceed the leaching toxicity discriminate standard of solid waste and so that MSWI fly ash is considered as a hazardous waste. The cement solidification effect of MSWI fly ash is also studied; The results show that the heavy metals in MSWI fly ash can be effectively solidified by mixing with cement. The main hydration products of cement and fly ash are as follows: calcium silicate hydrate, calcium aluminate hydrate, calcium hydroxide, Ettringite and calcium chloroaluminate. The heavy metals are immobilized within these hydration products through physical encapsulation, deposition, adsorption or isomorphous substitution mechanisms.