Evaluation of CO2 emission�absorption of fly-ash-blended concrete structures using cement-hydration-based carbonation model

Abstract

© 2014, RILEM. Concrete contains cement, which is known to emit large amounts of CO 2 in production, absorbs a certain amount of CO 2 by triggering a carbonation reaction with atmospheric CO 2 . However, this CO 2 absorption is generally neglected when evaluating the CO 2 emission from concrete. Thus, it is necessary to discover and consider ways to quantitatively evaluate the CO 2 absorbed by concrete. To this end, a carbonation model that can accurately predict the carbonation depth of concrete is necessary. However, the existing carbonation prediction equation is a simple regression equation that merely considers factors such as water–cement ratio and CO 2 concentration, and has a drawback as the results vary considerably form one researcher to another. Meanwhile, currently the use of fly ash, which is effective in reducing both of hydration heat and CO 2 emission and enhancement of long-age strength, is increasing. Thus, in the present study, a method for measuring CO 2 absorption by fly-ash-blended concrete structures using a carbonation model based on fly-ash-blended hydration was developed and evaluated. An apartment complex in which fly-ash-blended concrete was used is evaluated for its CO 2 absorption by using the developed method in this study. As a result, carbonation depth, amounts of CO 2 emission and absorption of fly-ash-blended concrete structure by design strength was obtained. The CO 2 absorbed by service life is approximately 3.79–8.47 % of the CO 2 emitted during the manufacturing of the concrete structure.