One of the largest contributors of the greenhouse gas emission is the production of cement for use in concrete. However, concrete is well-known for its carbon dioxide (CO2) uptake by carbonation. The purpose of this study was to consider the CO2 uptake in demolished and crushed concrete. In this study, three kinds of experiments and survey were carried out, including (1) an experiment using mortar specimens made in the laboratory so as to identify the conditions that accelerate CO2 uptake, (2) an experiment using concrete obtained from the demolition site and (3) a survey on the CO2 uptake in recycled crusher-run stone obtained from recycling plants. The experiment on new mortar and demolished concrete pointed out that the CO2 uptake in cement hydrate increases significantly when the particles are relatively small and when they are alternately wetted and dried. Furthermore, the survey on concrete at recycling plants found the amount of CO2 uptake in one ton of recycled crusher-run stone to be approximately 11 kilograms. Finally, using this value, the life cycle of CO2 of concrete structures was calculated and shown to be approximately 5.5% less when the CO2 uptake is taken into account compared to when it is not taken into account.