Effect of biochar from municipal solid waste on mechanical and freeze–thaw properties of concrete

Abstract

Global municipal solid waste (MSW) generation and cement manufacture pose catastrophic threats to the environment. Although positive impacts have been demonstrated for biochar originating from single biomass in concrete, limited studies focused on the biochar from the pyrolysis of municipal solid waste, and the freeze–thaw resistance of biochar concrete still remains unknown. This paper explored the feasibility of biochar derived from MSW at 600℃ to replace 1%-30% cement by weight in concrete. Properties of water absorption, setting time, mechanical properties and freeze–thaw resistance for the mixture systems were studied with the inspections of Scanning electron microscope (SEM), Fourier transforms infrared spectrometer (FT-IR) and X-ray diffraction (XRD). The results suggested that biochar replacement reduced the setting time of the binder system with an increase in water requirement of normal consistency. The compressive strength of concrete was increased by 9.2% with less than 5% of cement replaced. Biochar markedly improved the flexural and splitting tensile strength of concrete and thus played a beneficial role in toughness by 20% at 10% cement replaced. Concrete with a tiny proportion of biochar exhibited the weakest freeze–thaw resistance than control and 10% replacement. Biochar replacement promoted the formation of calcium carbonate. Biochar replacement for partial cement in concrete provides a sustainable option for municipal solid waste management and building energy consumption reduction.