Sustainable treatment approach to dumped construction waste with acids and CO₂ for its effective re-utilization in concrete

Dumping of construction wastes has become one of the serious concerns in the construction industries subsequent to the scarcity of construction materials, specifically aggregates. Extensive research works have been performed to utilize the dumped waste as aggregates, yet its substandard properties affect the concrete. Furthermore, several treatments were proposed to improve the quality of aggregates such as microbial, slurry etc, but the brittleness of concrete remains unavoidable. This research discusses the effect of acid treatment and carbonation treatment on recycled concrete aggregates (RCA) and the impact of hybrid fibres on concrete properties. The steel fibres (SF) and polypropylene fibres (PF) were optimized to 1.5% and 1.0% with 100% treated RCA to assess the concrete's hardened properties and water absorption. The study reports that the carbonation treatment to RCA performs better compared to acid treatment and the mix with the use of hybrid fibres shows enhanced properties than single fibres. The strength of the mix with 100% carbonated RCA 1.5% SF and 1.0% PF was 57% higher than that of recycled aggregate concrete (RAC) and the water absorption of similar mix was found to be lower than other mixes. Microstructural investigations through SEM and XRD were also performed to support the research findings.