Internal carbonation reinforcement of cementitious materials: Mechanism and performance
Ji‐Xiang Wang, Tianyong Huang, Caifu Ren, Guodong Cheng, Le Han, Yanbo Zhang, Ze Liu, Dongmin Wang
Abstract
Cement carbonation technologies are garnering increasing interest, but most CO 2 curing methods have limited on-site applications. In this study, a CO 2 internal curing route was presented and proven to be feasible. Zeolite NaX was selected as a CO 2 carrier due to its good adsorption capacity (16.2 g CO 2 /100 g drying zeolite) and stability (0.16% weight loss) at room temperature for internal carbonation of cement. CO 2 -saturated zeolite released the adsorbent once it was exchanged by water molecules during the mixing process, and the dissolved CO 2 in the paste solution produced carbonation products. It was discovered that, unlike the main products (calcite polymorphs) in CO 2 curing conditions, monocarbonate and calcite were the primary carbonation products in CO 2 internal curing cement composites . In addition to accelerating the hydration of C 3 S, zeolite NaX was found to react with cement systems and facilitate the formation of aluminocarbonates. The resulting composites exhibited quicker and higher strength development, increased modulus, reduced porosity, smaller pore intrusion radius, and minimal volume expansion. Moreover, the formation of monocarbonate was found to be correlated with the volume expansion of the composite system , as determined through thermodynamic calculations and autogenous shrinkage experiments. Finally, the composites exhibited a carbon sequestration capacity of 4.86 g CO 2 /100 g dry solid composites, with 71% of the CO 2 being solidified in minerals.