Enhancing the Durability of Reinforced Concrete Structures Using Carbonation-Inhibiting and CO2-Absorbing Microcapsules

Carbonation degrades reinforced concrete structures and reduces their service life, and it raises environmental concerns. Moreover, the cement industry faces increasing pressure to mitigate CO2 emissions. Therefore, this study developed a functional mortar incorporating microcapsule (MC) technology to suppress carbonation and enhance CO2 absorption. Two types of MCs were prepared: alkali-supplying MCs for carbonation resistance and CO2-absorbing MCs for carbon fixation. Mortars incorporating these MCs were evaluated using compressive strength tests, accelerated carbonation tests, and CO2 absorption measurements. The alkali-supplying MCs effectively suppressed carbonation, particularly at a dosage of 10%. However, the compressive strength decreased owing to the low strength and density of the MCs. The CO2-absorbing MCs significantly increased the CO2 uptake, particularly when impregnated with amines such as trioctylamine. However, they did not suppress carbonation, and their absorption capacities decreased over time. MCs without amine impregnation absorbed CO2, although they did not affect the carbonation depth owing to the absence of reactive components. These findings demonstrate the potential of MC-based mortars to improve the durability of concrete and promote carbon management. The use of cementitious materials with CO2-absorbing and protective functions is a promising approach for sustainable construction and long-term infrastructure resilience.