Hydration characteristics and modeling of ternary system of municipal solid wastes incineration fly ash-blast furnace slag-cement

Municipal solid waste incineration fly ash (MSWI FA) can be reused as an admixture in preparing various types of cementitious materials. In this work, MSWI FA was used as a supplementary cementitious material in combination with ordinary Portland cement and ground-granulated blast furnace slag (GGBFS). Mixture design modeling and Gibbs Energy Minimization Software (GEMS) were adopted to discuss the compressive strength and hydration characteristics of binary and ternary systems, respectively. A toxicity characteristic leaching procedure test of total Cr and Cr(VI) was conducted to analyze the environmental risk of MSWI FA-containing samples. The experimental data and the results of mixture design modeling suggested that, with an increase in MSWI FA in GGBFS-MSWI FA binary, the compressive strength exhibited an inverted 'V' shape. GGBFS could be activated by chloride and sulfate in MSWI FA to form ettringite and Friedel's salt in the GGBFS-MSWI FA binary system, according to the results of GEMS and X-ray diffraction. At nearly 0.55 of MSWI FA proportion in the GGBFS-MSWI FA system, the compressive strength and the modeling volume of ettringite and Friedel's salt reached their maximum. The concentration of leached Cr and Cr(VI) indicated that the hydrates from the solidified mixtures could reduce the leaching rate of total Cr and Cr(VI).