Synthesis and characterization of Europium-bonded acrylate-acrylamide hydrogel (P Eu-(AA-co-AM)): Structure and water absorption response

Acrylic-based hydrogels, are known for their remarkable water absorption and pH-responsive properties. These can release water to promote cement hydration and expand to fill cracks during the internal curing of concrete. However, their weak interfacial adhesion with concrete and shrinkage-induced micropore formation after the release of water compromise their curing efficienciesy. To address these limitations, this study synthesized europium-bonded acrylic-acrylamide hydrogels (PEu-(AA-co-AM)). Additionally, it systematically investigated the effects of europium bonding on the polymerization behavior, network structure, and water absorption responsiveness, as well as their performance in concrete curing and crack self-healing.The results demonstrated that the reactivity ratios of acrylic acid (AA), acrylamide (AM), and europium acrylate (Eu(AA)₃) were less than one, This indicated a preference for copolymerization, which facilitated the uniform distribution of europium ions within the hydrogel network. The incorporation of Eu ions significantly increased the crosslinking density and water retention capacity of the hydrogel. It imparted a second-order swelling response under varying pH conditions, with a significant increase in the swelling ratio at high pH. Furthermore, compared with unmodified hydrogels, PEu-(AA-co-AM) reduced the porosity of concrete, enhanced the compressive strength, and improved the crack self-healing efficiency. This study has provided theoretical insights and potential applications for the design of europium-bonded hydrogels with superior water-responsive properties for concrete engineering applications.