Nano-CaCO₃ enhances PVA fiber-matrix interfacial properties: an experimental and molecular dynamics study

The mechanical properties of fiber-reinforced concrete largely depend on its interfacial properties. Fibers with a low aspect ratio are often pulled out at the fracture surface, and the potential of fiber-reinforced concrete is far from being fully realized. This is because the fiber-matrix interface bond strength is weak, resulting in low fiber reinforcement efficiency? which is the main challenge for organic fiber reinforced concrete. To further optimize the reinforcing and toughening effect of fibers on concrete, in this study, nano-CaCO3 was used to treat PVA fibers by a sol-gel method, aiming to enhance the interfacial bonding properties of fiber-reinforced concrete. The mechanical properties test results show that the compressive strength and flexural strength of the modified PVA fiber reinforced concrete are increased by 8.1% and 35.95%, respectively. Finally, Molecular dynamics simulation results reveal the interaction mechanism between CaCO3 and the cement matrix-fiber interface. The CaC-S-H-OCaCO3 forms a high-strength interfacial connection and is stronger than the H bond formed at the C-S-H/PVA interface. Therefore, the C-S-H/CaCO3 interface interaction energy far exceeds that between C-S-H/PVA. Comprehensive analysis shows that nano-CaCO3 enhances the interfacial bonding performance of fiber-matrix, which has certain theoretical reference significance for developing high-performance fiber reinforced concrete.