Quasi-static and dynamic mechanical properties of concrete containing cellulose fiber: Mechanism and effects

Concrete structures are susceptible to fracture at different strain rates. The aim of this study was to investigate the multi-scale mechanism and effects of eco-friendly cellulose fibers on quasi-static and dynamic mechanical properties. The quasi-static and dynamic mechanical properties of concrete were investigated using a hydraulic servo system, pullout test, direct tensile test, drop hammer test, and split-Hopkinson pressure bar (SHPB). The effects of cellulose fibers on the hydration and microstructure of the cementitious composites were characterized via thermogravimetric analysis (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests. Through molecular dynamics (MD) investigations, this study deciphered the atomistic origins of mechanical enhancement in cellulose-modified cementitious composites, establishing quantitative correlations between macroscopic performance metrics and the underlying chemical-structural determinants. Finally, the reinforcement mechanisms of the cellulose fibers in the cementitious composites under varying strain rates were systematically investigated. The mechanism of cellulose fiber reinforcement in concrete involves regulated moisture release from fiber cavities during hydration equilibrium, induction of calcium hydroxide precipitation through solution dilution, and promotion of pore structure densification via controlled humidity gradient attenuation. This self-limiting process enhances the mechanical strength by optimizing interfacial transition zone integrity through hydrostatic pressure-mediated crack deflection and energy dissipation mechanisms, effectively converting the impact energy into elastic strain energy through strategically modified fracture pathways.