Utilising CO2 technologies for recycled aggregate concrete: A critical review.

• CO 2 injection into concrete and recycled aggregate concrete made improvement. • Carbonation of recycled aggregate is generally quicker and easier than concrete. • Concrete carbon-curing is effective, but is less practical than recycled aggregate. 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 CO 2 into cementitious materials has been studied, for both improving the overall quality of recycled aggregate concrete as well as permanently chemically converting CO 2 into stone. CO 2 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 CO 2 into concrete: (1) carbon-conditioning is the injection of CO 2 into recycled aggregate; and (2) carbon-curing involves sequestering CO 2 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 CO 2 technologies for concrete improvement. [ABSTRACT FROM AUTHOR]