Application of ferronickel slag as fine aggregate in recycled aggregate concrete and the effects on transport properties

Abstract

Industrial and construction solid waste regarded as a hazardous material has given rise to the potential threats of environmental pollution. The ferronickel slag (FNS) as an industrial by-product and recycled concrete aggregates (RCAs) derived from construction and demolition wastes have potential for sustainable use as the fine and coarse aggregate in concrete, respectively. However, less information regarding the re-utilization of FNS as fine aggregate in recycled aggregate concrete (RAC) and the effects on transport properties can be found in the previous literature. The aim of this study is to investigate the compressive strength and transport behavior of RAC incorporating FNS as fine aggregate. In this study, several groups of specimens with different replacement ratios of FNS as fine aggregate (0, 20%, 40% and 50%) and RCAs (0, 50% and 100%) as coarse aggregate were prepared. The compressive strengths of FNS-RAC specimens at curing age of 3, 7 and 28 days were measured. The coupled effects of FNS and RCAs on the resistance to water absorption and chloride penetration of concrete were discussed. To explore the effect of microstructure on transport behavior, the tests of scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were further conducted. Overall, the sorptivity and chloride diffusion coefficient increase as the RCA replacement ratio increases, but they generally decrease with increasing of FNS content. The mixtures containing 40%–50% FNS fine aggregate in RAC exhibit the greater compressive strength and better resistance to transport behavior.