Use of eco-admixture made from municipal solid waste incineration residues in concrete

Abstract

With the phasing-out of coal power plants in many developed countries, a steep shortage in construction-grade fly ash – a widely used mineral admixture in concrete – seems inevitable. In this study, an eco-admixture prepared from a raw blend of municipal solid waste incineration (MSWI) residues was investigated as a possible cement replacement in concrete. The eco-admixture was synthesized at incineration temperature of 1100 °C from a carefully selected stoichiometric combination of three residues sourced from a local incinerator and minor additions of slaked lime. Paste and concrete specimens were prepared with 15% cement replacements and compared to commercial mineral admixture and ordinary Portland cement (OPC) control. In addition to normal hydration, carbonation was explored as an alternative curing scenario for accelerated early strength activation. The influences of cement substitution on mechanical properties, leaching performance, microstructure, and resistance to freeze-thaw damage were examined. The major reactive mineral components of eco-admixture were found to be belite and chloro-ellestadite. In hydration, paste and concrete specimens containing eco-admixture were comparable in performance to straight OPC control; however, they displayed much improved strength and resilience when activated by carbonation. Leaching tests affirmed the environmental stability and suitability of eco-admixture as a supplementary cementitious material (SCM) in concrete. For further validation, a pilot production was carried out at a commercial concrete plant to produce a cubic meter of standard 20 cm concrete masonry units (CMUs). The CMUs with eco-admixture displayed comparable strength to the OPC references and satisfied all physical performance required by load-bearing standards.