Pozzolanic Properties of Municipal Solid Waste Incineration (MSWI) Fly Ash Under the Actions of Three Different Activators

This study investigated the pozzolanic capacity of MSWI fly ash in the solidification process. The MSWI fly ash were solidified by using three kinds of activators, i.e., Na2CO3, CaSO4 and Na2SiO3, they were all cured for 7 and 28 days. Each of them involved two cases, i.e., the activator mixing proportions were 3 and 6% in dry mass basis, respectively. After that, the unconfined compressive strength (UCS) test and water immersion test were conducted on the solidified samples, to investigate the influence of the kind and proportion of activator on MSWI fly ash solidification. The results showed that all the three kinds of activators had played a role in promoting the solidification process, and the Na2CO3 performed best. The UCS value of the samples with the action of Na2CO3 enhanced with the increase of activator mixing proportion and curing time. The 28-day UCS value of the sample with Na2CO3 mixing proportions of 6% reached 2.924 MPa, and the solidified sample also showed a good water tolerance. The effect of CaSO4 on the MSWI fly ash solidification was complex. The UCS value increased with the curing time when the CaSO4 mixing proportion was 3%, however, it decreased with the curing time when the CaSO4 mixing proportion was 6%.