Chloride-ion-triggered microcapsule for self-suppression of capillary suction in cement paste

In this study, we developed a novel microcapsule that could be triggered by chloride ions (Cl−). The microcapsule had a multicore structure achieved by crosslinking carboxymethyl cellulose (CMC) networks with silver nanocrystals (Ag NCs) and encapsulating graphene oxide (GO)/methyl palmitate (MPA) emulsion droplets as sub-microcapsules. Upon triggering, the sub-microcapsules were released, reducing the capillary suction effect by imparting hydrophobic properties to microcrack and pore walls. To investigate the distribution and triggering process of the microcapsules in cement paste, X-ray micro-computed tomography (XCT) was employed. The experimental results demonstrated that the microcapsules could be stably distributed throughout the cement paste. In specimens with 1% microcapsules, a 74.3% decline in capillary water absorption was observed after two-week wet-dry cycles, indicating the efficacy of the microcapsules in reducing water ingress into the cement paste. Moreover, the microcapsules exhibited a slow reduction in size after multiple triggering events, as characterized by XCT, suggesting that they could provide repeatable protection for cementitious materials.