Exploring the origin of carbon in concrete materials using 14C

Abstract

The product formed by the reaction of cement and water is called cement paste, which is mainly composed of calcium silicate hydrate and serves as a binding agent for concrete. CaO, the main component of cement, is obtained from the decomposition of CaCO3, which generates CO2. On the other hand, concrete reacts with CO2 in the atmosphere to produce calcium carbonate (carbonation reaction). We are trying to achieve carbon neutrality by immobilizing atmospheric CO2 into cementitious materials in the form of inorganic carbonates. Wang et al. (2023) exposed cement paste to air and determined the concentration of radiocarbon (14C) in the paste before and after the exposure. We found that the amount of atmospheric CO2 fixed can be evaluated by determining the concentration of radiocarbon (14C) in the paste before and after exposure to air. In order to apply this evaluation method to actual concrete in the future, the initial 14C value of the entire concrete must be known. Therefore, in this study, 14C measurements of raw materials such as cement, aggregate, and admixture in concrete were conducted, and the results will be presented