Performance and mechanism of dual-network cementitious material formed by acrylamide monomer in-situ polymerization and ultra-fine portland cement

Grouting engineering is extensively employed in highway maintenance, tunnel excavation, mining, and other domains. As application scenarios become more complex, the demands for injectivity and toughness of grouting materials escalate. This research presents the fabrication of a dual-network cementitious material through acrylamide (AM) monomers in-situ polymerization and ultra-fine portland cement for grouting. The in-situ polymerization of AM increases the fluidity of cement paste, forms a hydrogel three-dimensional network structure, and significantly reduces the initial setting time from 345 to 35 min at a 5% AM content. The early-stage compressive strength (0–7 days) is inhibited by the in-situ polymerization, the flexural strength is notably increased, with an overall toughness improvement of 174.4% at a 7% AM content. The in-situ polymerization influences the early hydration behavior of ultra-fine portland cement by delaying the hydration induction period and affecting calcium hydroxide content and the bound water in calcium silicate hydrate. The complexation between metal ions (Ca²⁺, Al³⁺) in ultra-fine portland cement and carboxyl groups in the polymer enhances organic–inorganic interaction. The three-dimensional network structure of the cement hydration products and the polymer will form a dual-network structure, further enhancing the performance of the ultra-fine portland cement. In this research, the potential application of AM in-situ polymerization in the enhancement of ultra-fine portland cement grouting is proposed.