Abstract

In this study, two types of municipal solid waste incineration (MSWI) bottom ash (BA) (MSWI-BA-A, water quenched, MSWI-BA-B, natural cooling), are utilized as alternative materials for clinker sintering. Fixed clinker modulus (lime saturation ratio = 0.90 ± 0.01, silica modulus = 2.6 ± 0.1 and alumina modulus = 1.5 ± 0.1), designed gradient addition ratio of MSWIBA (0, 3%, 6%, 9% and 12%) and same sintering temperature (1723.15 K) are adopted to conduct the experiments. Raw materials are characterized by XRF, X-ray diffraction and differential thermal analysis. Clinkers are analyzed and evaluated by XRF, X-ray diffraction, petrographic analysis, compressive and flexural strength tests and toxicity characteristic leaching procedure. The major difference of the two types of MSWIBA is LOI value which is supposed to be the most probable reason for huge difference between liquid phase formation temperature variation and incremental introduction of MSWI. MSWI-BA-A increases liquid phase formation temperature. Liquid phase formation temperatures and MSWI-BA-B samples addition ratios nearly present negative linear correlation. All clinkers sintered with addition of MSWIBA slightly reduce water demand for normal consistency. MSWIBA addition poses relatively obvious influence on initial setting time and little effect on final setting time. There is an increase in initial strength and a decrease in 28-day strength of clinkers sintered with MSWIBA, 28-day compressive strength decreases with the incremental introduction of MSWIBA. Distinct characteristics, such as free lime, periclase, orthorhombic tricalcium aluminate (C₃A) crystal and secondary Belite crystal, are observed by petrographic analysis. MSWIBA is significant source of free lime and periclase in clinkers. Incremental input of alkali introduced by MSWIBA influences clinker sintering and mineral crystallinzation, further results in orthorhombic C₃A crystal and indistinct Alite edge caused by corrosion. Leaching concentration of heavy metals from mortars prepared with the sintering clinkers is lower than corresponding concentration of the Chinese National Standard GB 30760-2014.

Graphic abstract