Enhanced adhesion strength of polyacrylamide-tannic hydrogel to concrete surface through reactive particle aggregation of calcium aluminate cement

Hydrogel-based functional devices hold transformative potential for application in construction, yet reliable interfacial adhesion to concrete remains a critical barrier for the large-scale implementation. In this study, the reactive particle aggregation behavior of calcium aluminate cement (CA) is strategically incorporated into polyacrylamide-tannic acid (PAM-TA) hydrogel to provide reliable adhesion to cracked concrete. CA aggregation promotes the formation of rigid aggregates within the hydrogel network, generating a marked modulus gradient. This gradient induces localized stress concentration zones around the aggregates. While moderately reducing bulk toughness and elongation, these zones prioritize triggering concentrated energy dissipation prior to interfacial failure, thereby doubling the concrete adhesion strength (48.05 kPa) versus CA-free control. The optimized hydrogel further demonstrates rapid, watertight sealing of variable-width concrete cracks within 10 s, establishing its practical potential as a high-performance temporary sealant. This study presents a novel strategy to enhance the adhesive strength of hydrogels, while also paving a feasible path for the development of smart building materials.