Toward carbon balance in life cycle: the carbon emission assessment for the recycled coarse aggregate concrete

The “carbon balance” theory is introduced into the investigation on carbon emission throughout the recycled coarse aggregate concrete’s life cycle. It is aimed to study the carbon sink effect on the operation concrete stage, reveal the carbon balance of the recycled coarse aggregate concrete in its life cycle, and design low-carbon concrete based on concrete performance and environmental impact. Considering the carbon adsorption effect, the recycled coarse aggregate concrete’s life cycle can be divided into four stages. In addition, the calculation model for carbon emission is constructed to estimate the carbon emission throughout the recycled coarse aggregate concrete’s life cycle. The results concluded that the carbon emission was mainly concentrated in the production and transportation stages of concrete composition raw materials, and the carbon sequestration effect through the concrete operation stage cannot be ignored. The carbon sequestration effect obviously increased with the strength grade of the recycled coarse aggregate concrete and the replacement rate of the recycled coarse aggregate increasing. The transportation distance of coarse aggregate in concrete composition materials is the most sensitive factor to the effect of carbon emission on the recycled coarse aggregate concrete. Compared with the ordinary concrete, the recycled coarse aggregate concrete has significant carbon reduction advantages, with 1 m³ of the recycled coarse aggregate concrete reducing carbon emissions by 70–100 kg. The research findings also provided empirical reference for the government to reduce carbon management on the construction sector from the perspective of carbon balance.