This paper investigates effect of colloidal nano-SiO₂ (CNS) on chloride immobilization of cement-fly ash (FA) system composed of 70% cement and 30% FA from 7 d to 90 d age. The mechanism is revealed in terms of migration resistance, chemical binding, and physical binding; and each aspect is determined with corresponding measurements, including microstructure of hydrates examined by XRD, EDS, TGA and NMR, and pore structure evaluated by MIP. Results reveal that the CNS dosage influences immobilized chloride ratio (ICR). 0.5% CNS promotes the ICR, while more than 0.5% CNS would decrease ICR. The promotion by 0.5% CNS is derived from the refined pore structure and the increased amount of C-S-H gel, which could enhance the migration resistance and physical binding; the decrease by more than 0.5% CNS is because of the reduced amount of chloroaluminates and the decreased Ca/Si ratio, leading to the decline in chemical binding and physical binding. Furthermore, curing age also affects ICR. 28-day ICR is higher than that at 7 d or 90 d. The increase of ICR from 7 d to 28 d is attributed to the refinement of pore structure and the increase in amount of chloroaluminates and C-S-H gel; reduction from 28 d to 90 d age is due to the negative effects including the decrease in content of chloroaluminates and the reduced Ca/Si ratio. The findings are expected to give new insight into the effect of nano-SiO₂ on performance of cement-based materials.

本文研究了纳米SiO ₂胶体的作用（CNS）在7 d至90 d年龄对由70％水泥和30％FA组成的水泥-粉煤灰（FA）系统进行氯化物固定的研究。从抗迁移性，化学结合和物理结合方面揭示了该机制。并通过相应的测量来确定各个方面，包括通过XRD，EDS，TGA和NMR检查的水合物的微观结构，以及通过MIP评估的孔结构。结果表明，中枢神经系统的剂量会影响固定的氯化物比率（ICR）。0.5％的CNS会提高ICR，而0.5％以上的CNS会降低ICR。0.5％的CNS促进作用来自细化的孔结构和CSH凝胶量的增加，这可以增强抗迁移性和物理结合力；CNS减少量超过0.5％是因为减少了氯铝酸盐的量，并且减少了Ca / Si比，导致化学结合和物理结合的下降。此外，固化年龄也会影响ICR。28天ICR高于7天或90天。ICR从7 d增加到28 d是由于孔结构的细化以及氯铝酸盐和CSH凝胶的数量增加所致。从28 d到90 d的减少是由于负面影响，包括氯铝酸盐含量的减少和Ca / Si比的降低。这些发现有望为纳米SiO的作用提供新的见解。从28 d到90 d的减少是由于负面影响，包括减少氯铝酸盐含量和降低Ca / Si比。这些发现有望为纳米SiO的作用提供新的见解。从28 d到90 d的减少是由于负面影响，包括氯铝酸盐含量的减少和Ca / Si比的降低。这些发现有望为纳米SiO的作用提供新的见解。₂关于水泥基材料的性能。