A scientific rationale for the enhanced sequestration of CO2 in concrete

Abstract

Oxford Economics forecasts that concrete construction will grow by 85% to USD 8 trillion worldwide by 2030 and will lead to significant usage of Portland cement (PC). Every 1 kg of PC production generates ≈0.8 kg of CO 2 , which is about 1.5 Gt of CO 2 emission per year for PC production. One of the ways to reduce the carbon footprint of concrete is by sequestrating CO 2 using of the following approaches: (i) pre-carbonation; (ii) wet-carbonation; or (iii) CO 2 curing of concrete in various types of carbonation chambers. The efficiency of these methods is measured by calculating CO 2 Sequestration Factor (CSF). It is reported that the CSF of carbonation curing approach is 10 to 15%. However, it was found that the method used for calculating CSF does not consider the un-carbonated parts of the specimens, hence it does not represent the actual efficiency of the CO 2 sequestration methods. Therefore, modification for calculating the CSF is proposed in this paper. Using the modified method, it was found that the CSF of carbonation curing method is less than 2% and wet carbonation is the most efficient method (≈30%). Further, a way forward is proposed to enhance the CO 2 sequestration in concrete, which will not compromise fresh or hardened properties of concrete and would significantly contribute to the net zero carbon agenda compared to existing approaches