In our pursuit to comprehend the carbon dioxide (CO2) absorption characteristics of concrete through empirical investigation, an experimental setup was previously designed. This apparatus consisted of a sealed container and a CO2 concentration meter. The experimental procedure involved placing concrete specimens and the CO2 concentration meter inside the sealed container, injecting CO2 until the concentration reached approximately 5%, and subsequently measuring the reduction in CO2 concentration over time. The objective was to elucidate the CO2 absorption properties of the concrete specimens. The results unveiled that the CO2 absorption properties of concrete are contingent upon the water-cement ratio and are susceptible to factors such as the number of specimens and the type of fine aggregate. Additionally, the study suggested the presence of a limit to the CO2 absorption performance of concrete. Based on these findings, the study focused on cement, which is considered to have the most significant impact on the CO2 absorption characteristics of concrete. Mortar specimens were consequently prepared and subjected to CO2 absorption experiments. The absorption characteristics and the estimated capacity for CO2 absorption were calculated. The results indicated a gradual reduction in the ability of specimens to absorb CO2 with repeated CO2 exposure. Furthermore, the capacity for CO2 absorption in the specimens could be estimated.