纳米纤维素（nano cellulose fibers, CNFs）在水泥基材料的碱性环境中易发生水解与矿化，限制了其在水泥基材料中的广泛应用。在添加CNFs的水泥砂浆中复掺纳米二氧化硅（nano-silica, NS），通过抗压强度、抗折强度以及断裂韧性研究二者的协同效应，试验结果表明，复掺NS可以显著提高水泥砂浆的力学性能，在复掺1.5%掺量的NS时，砂浆90 d抗压强度相比单掺组可提高22.4%，其断裂韧度相比单掺组可提升89.1%。通过低场核磁共振技术（low-field nuclear magnetic resonance technology, NMR）、热重分析仪（thermogravimetric analyzer, TGA）以及电子扫描电镜（scanning electron microscope, SEM）对微观结构进行分析，试验表明，纳米二氧化硅可以与氢氧化钙进行二次水化反应，消耗水化产物中的氢氧化钙，防止纳米纤维素矿化的同时产生大量的水化硅酸钙［Ca₅Si₆O₁₆(OH)·4H₂O, C-S-H］凝胶，进而提高基体的密实度，增强纳米纤维与基体的黏结能力，有效抑制内部微裂纹的产生和发展。

Nano cellulose fibers (CNFs) are recognized as being susceptible to hydrolysis and mineralization in the alkaline environment of cement-based materials, which restricts their broad application in such systems. Nano silica (NS) was combined with CNFs in cement mortar. The synergistic interaction between the two components was examined through compressive strength tests, flexural strength measurements, and fracture toughness evaluations. The addition of NS is shown to significantly enhance the mechanical properties of cement mortar. When 1.5% NS is incorporated, the 90-day compressive strength of the mortar is observed to increase by 22.4% compared to the single additive group. Its fracture toughness is found to improve by 89.1% relative to the single additive group. The microstructure is characterized using low-field nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Calcium hydroxide in hydration products is consumed through a secondary hydration reaction with nano silica. This process can inhibit the mineralization of nano cellulose. Simultaneously, abundant Ca₅Si₆O₁₆(OH）·4H₂O(C-S-H) gel is generated, resulting in improved matrix density. The bonding capacity between nano fibers and the cement matrix is strengthened. The initiation and propagation of internal microcracks are effectively suppressed. The compactness of the composite material is enhanced through these mechanisms.