Study of strength stability of municipal solid waste incinerator fly ash solidified by cement

According to the technical requirements of safe disposal of municipal solid waste incinerator (MSWI) fly ash, the fly ash is solidified by cement. The unconfined compression strength and destruction characteristics of fly ash solidified blocks with different cement contents, curing times and soaking times are studied. Then the erosion mechanism of leachate is analyzed. The test results show that the fly ash solidified blocks are destructed quickly after soaking in leachate with cement content less than 5% and curing time less than 3 days. The erosion of leachate has a great influence on the strength of fly ash solidified blocks. The fly ash solidified blocks present an obvious strain softening characteristic after soaking. The strength of fly ash solidified blocks without soaking in leachate accords with the mode of y=a[1-exp(-bt)]. With the increase of cement content and curing time, the unconfined compression strength increases and the failure strain decreases. But with the increase of soaking time, the strength increases firstly and then decreases; the turning point is about on 5-7 days; and the failure strain increases linearly. The erosion mechanism is that leachate can inhibit hydration reaction and destroy hydration products of fly ash solidified blocks. The results can provide theoretical basis and data support for the safe disposal of MSWI fly ash.