Deposition methods to enhance performance of recycled concrete and brick aggregate for high-grade concrete production

Abstract

Construction demolition waste, for instance, recycled concrete and brick aggregate could be a serious contender to minimize the uninhibited utilization of virgin aggregate, reducing detrimental environmental impacts. Nevertheless, the utilization of this is limited owing to the inherent inferior physical, microstructural and mechanical properties. For instance, this has high porosity, low-density, high water absorption and micro cracks. The recycled concrete and brick aggregate is largely utilized for the land fill and minor utilization for the production of low-grade concrete. Thereby, the recycled concrete and brick aggregate were improved to enable a wider adoption of this for high-grade concrete applications.

This research provided insight and investigated the experimental evidence into the identification and development of novel methods to improve physical, microstructural and mechanical properties of recycled concrete and brick aggregate, and exceeded these properties of virgin aggregate, for high-grade concrete applications. Consequently, gained an understanding of the effects of the treatment methods. The recycled concrete and brick aggregate were treated with different treatment methods and chemicals in a reaction chamber and the improved recycled concrete and brick aggregate were verified in terms of particle density, water absorption, crushing value, particle size distribution, misshapen particles percentage and flakiness index, in accordance with Australian standards. Moreover, the 'copper deposition' with 'copper formate (Cu(HCOO)2)' method was selected as the optimum treatment method based upon the data.

The X-ray diffraction performed with the diffractometer confirmed the copper depositions in the voids of the aggregate and the chemical properties. The scanning electron microscopy (SEM) analysis evinced the microstructural and physical improvements of the recycled concrete and brick aggregate with healed cracks, strong bonds of the copper to the adjacent surface in the voids, improved density, and the improvements to the interfacial transition zones (ITZ). The life cycle assessment for the 'copper deposition' method, evinced environmental impacts in terms of global warming, stratospheric ozone depletion, ionizing radiation, fine particulate matter formation, photochemical ozone formation, terrestrial acidification, freshwater eutrophication, marine eutrophication, toxicity, water use, land use, mineral resource scarcity and fossil resource scarcity.

The concrete produced mixed with the treated recycled aggregate using the 'copper deposition' method evinces excellent performance compared to concrete mixed with untreated recycled aggregate and virgin aggregate. This decreases uninhibited utilization of virgin aggregate, reduces environmental impacts and allows a wide adoption of this to produce high-grade concrete.

Date of Thesis submission	2023
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Vivian Tam (Supervisor), Anthony Butera (Supervisor), Khoa Le (Supervisor) & Mahfooz Soomro (Supervisor)