Utilising CO2 technologies for recycled aggregate concrete: A critical review

Employment of recycled aggregate within concrete provides great potential for the reduction of landfilling. Unfortunately, recycled aggregate exhibits a high porosity and water absorption and consequently produces a substandard material when compared to the mainstream virgin aggregate concrete. Recently, the injection of CO2 into cementitious materials has been studied, for both improving the overall quality of recycled aggregate concrete as well as permanently chemically converting CO2 into stone. CO2 treatment can permit recycled aggregate concrete to rival virgin aggregate concrete in phycial and mechanical properties. Currently, there are two primary methodologies for the sequestration of CO2 into concrete: (1) carbon-conditioning is the injection of CO2 into recycled aggregate; and (2) carbon-curing involves sequestering CO2 into new concrete’s cement paste. Whilst both technologies permit recycled aggregate concrete for achieving great mechanical property and durability, carbon-conditioning provides a practical implementation. Carbon-conditioning permits a prompt and complete carbonation of recycled aggregate which enhances the final concrete’s mechanical property and durability. This paper provides an insight into the available CO2 technologies for concrete improvement.