A scientific rationale for the enhanced sequestration of CO2 in concrete

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 CO2, which is about 1.5 Gt of CO2 emission per year for PC production. One of the ways to reduce the carbon footprint of concrete is by sequestrating CO2 using of the following approaches: (i) pre-carbonation; (ii) wet-carbonation; or (iii) CO2 curing of concrete in various types of carbonation chambers. The efficiency of these methods is measured by calculating CO2 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 CO2 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 CO2 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