Interfacial Bonding Mechanism between Mineral Fillers and Acrylate Composite Polyurethane Binder: Insights from...

The mineral filler/acrylate composite polyurethane binder (APUB) composite mortar shows significant potential for ecofriendly steel bridge deck paving due to its ability to cure at ambient temperature and high toughness. However, the unclear interfacial bonding mechanism between mineral fillers and APUB hinders the design and optimization of the high-performance composite mortars. This study systematically investigates the interfacial bonding mechanism of three mineral fillers (cement, limestone powder, and fly ash) within APUB by integrating macro-experiments (dynamic shear rheology and nanoindentation tests) and molecular dynamics (MD) simulations. The macro-experimental results indicate that the cement-APUB interface exhibits optimal bonding, displaying the highest static elastic modulus (0.42 GPa) and hardness (20.19 MPa) in the interfacial zone, which contributes most significantly to the dynamic viscoelastic and static mechanical response of the composite mortar. MD simulations further reveal that the interfacial binding energy between APUB and representative filler oxides follows the order: SiO₂ > CaO > MgO > Fe₂O₃ > Al₂O₃. The dominant interfacial mechanism shifts from electrostatic and van der Waals forces under dry conditions to hydrogen bonding under wet conditions. Crucially, water molecules create a separation effect at APUB interfaces with Al₂O₃, Fe₂O₃, and MgO while forming dual hydrogen bonds that create a novel bridging effect at APUB-SiO₂ and APUB-CaO interfaces, thereby enhancing interfacial adhesion. This study elucidates the mechanism by which the chemical composition of mineral fillers determines the macroscopic performance by regulating interfacial molecular interactions, providing a theoretical basis for the rational selection of fillers and the design of high-performance, resource-efficient mineral filler/APUB composite mortars, particularly for durable steel bridge deck paving applications.