Physical properties of recycled concrete powder and waste tyre fibre reinforced concrete

The environmental concerns of cement manufacturing prompted researchers to study other cementitious materials that are easily available, low cost, and also contribute to improved sustainability. This research was carried out for the utilisation of recycled concrete powder (RCP) as cement replacement with different replacement ratios, including 5%, 10%, and 15%. Furthermore, to improve the tensile behavior, steel fibers (2.0%) were added as reinforcement. This part discusses the challenges of managing demolition construction waste, waste rubber tires, and the physical and chemical properties of RCP. Fresh properties were assessed through setting times, fresh density, and slump cone tests, and physical properties were evaluated through hardened density, water absorption, permeability, and ultrasonic pulse velocity. The change in internal structure and pozzolanic reactivity were evaluated through scanning electron microscopy (SEM) and an X-ray diffraction (XRD) test. Results indicate that RCP decreased concrete workability and increased setting time and fresh density. Furthermore, improvements in the physical properties of concrete were noted with 5.0% RCP substitution, which shows 25% lower water absorption and 13.8% lower permeability at 28 days. The SEM and XRD results reveal that RCP possesses micro-filling and cementitious properties.