Mechanical properties of CO2 concrete utilising practical carbonation variables

The injection of CO2 into concrete, recycled aggregate and other cementitious materials provides potential for both sequestration of undesirable gas and strengthening of said materials. This paper endeavours to extend upon CO2 injection research by comparing carbon-conditioned recycled aggregate concrete (named as CO2 Concrete) to virgin aggregate concrete in terms of mechanical performance. To complete this objective, a primary investigation is to experiment different carbonation variables such as carbonation duration and pressure. A secondary investigation provides a starting point for further research by mixing carbonation technology with other supplementary concrete strengthening procedures. The primary investigation found that a practical 2-h carbonation duration couple with a low pressure of 25 kPA provided the best strengthening of mechanical properties. CO2 Concrete with 30% and 50% recycled aggregate replacement is very comparable in performance when rivalled against virgin aggregate concrete. Furthermore, CO2 Concrete with 100% replacement of virgin aggregate generally exceeded the control recycled aggregate concrete by 20% and achieved a mechanical property very close to that of the virgin aggregate concrete. However, whilst CO2 Concrete experienced an excellent enhancement, the modulus of elasticity of the environmental concrete must be improved as virgin aggregate concrete still surpasses CO2 Concrete by a fair margin. The secondary investigation shows that the mixing of techniques such as the two-stage mixing approach and carbonation of recycled aggregate can be used in conjunction with each other. This paper provides insight with evidence for the potential practical applications of CO2 Concrete.