Utilization of municipal solid waste incinerator fly ash as a partial aggregate replacemant in cement mortars

Abstract

The research was conducted to investigate characteristics of two types of municipal solid waste incinerator fly ash (MSWIFA) ; sprayed and non-sprayed, collected from a mass-burn incinerator in Phuket, Thailand. Solidified MSWIFA was applied to replace natural sand for producing MSWIFA cement mortars. The following physical and chemical characteristics were determined ; particle size distribution, bulk chemical and mineralogical compositions, total heavy metals, and leached heavy metals. Preliminary treatment of MSWIFA was carried out for chloride reduction by washing. Then, the washed MSWIFA was mixed with cement in solidification and stabilization (S/s) process to produce recycled aggregate and then compared their properties with natural sand. Cement mortar specimens containing recycled aggregate were examined for developments of compressive strength. The recycled aggregate cement mortars were as well evaluated for impacts on environmental safety and public health. The results showed that sprayed MSWIFA particles were bigger than those of non-sprayed MSWIFA. Although heavy metals from the both types were present in small amounts, concentrations of lead (Pb) and selenium (Se) exceeded the regulatory limits. From the preliminary treatment, it was found that high amount of chloride was dissolved in wash water. That was consistent with high chlorides determined in the chemical composition analyses. Comparison between recycled aggregate and natural aggregate showed that the recycled aggregates had a potential to be used as an admixture in concrete construction. Moreover, the development of compressive strength of cement mortar specimens at 28 days of curing age demonstrated that the compressive strengths of cement mortars containing 20 percent by weight of sprayed recycled aggregate was the highest. The group of specimens containing 10 percent sprayed fly ash possessed the highest strengths even when compared with control specimens. The 28-day cement mortars containing recycled aggregates were investigated for leachate characteristics by extraction procedure described in the Notification of Ministry of Industry No.6 B.E.2540 (1997).the results showed that the concentrations of heavy metals in the leachate of all specimens met the regulatory limits.