Effect of biomineralization technique on the strength and durability characteristics of recycled aggregate concrete

The recycling of waste in concrete prevents the depletion of natural resources, preserves the environment and also manages the disposal of waste. As aggregates in concrete are in higher volume, hence using construction and demolition waste (CDW) as recycled aggregate would make concrete construction more sustainable. In this study, the technique of biomineralization has been addressed to improve the strength and durability properties of recycled aggregate concrete (RAC). For this, RAC mixes with and without bacteria were prepared with 50% and 100% recycled coarse aggregate (RCA). The compressive strength, water absorption, water permeability, electrical resistivity, durability against sulfate resistance of concrete were tested. In addition, microstructure analysis of concrete was carried out using SEM, EDS and XRD. Tests for durability were performed on 28, 56, 120 days and for strength on 7, 28, 56, 120 days. Results show that the compressive strength of 100% RAC concrete was increased by 19.0% on 120 days from the CaCO3 precipitations accumulated by bacteria and durability properties in terms of water absorption, water permeability, electrical resistance were also enhanced by 12.7%, 42.9%, 100.8% respectively The bacterial activity could resist the penetration of sulfates and hence improved strength performance was recorded in the sulfate environment of the bacterial recycled aggregate concrete (BRAC). Moreover, the presence of crystals of bacterial CaCO3 precipitation and sulfate salts were observed in the micrographs of SEM, which was confirmed by the results of EDS and XRD analysis. Further, the benefit-cost ratio reveals that the improvements that have been achieved in 100% RAC properties with bacteria show that 100% BRAC pro-duction is economically feasible. (C) 2021 Elsevier Ltd. All rights reserved.