[4] [4] LIU P, CHEN Y, WANG W L, et al. Effect of physical and chemical sulfate attack on performance degradation of concrete under different conditions[J]. Chemical Physics Letters, 2020, 745: 137254.

[5] [5] ZHANG G Z, WU C, HOU D S, et al. Effect of environmental pH values on phase composition and microstructure of Portland cement paste under sulfate attack[J]. Composites Part B: Engineering, 2021, 216: 108862.

[7] [7] FAN C C, ZHENG Y X, ZHUO J B, et al. Study on mechanical and bonding properties of nano-SiO2 reinforced recycled concrete: macro test and micro analysis[J]. Journal of Building Engineering, 2024, 94: 109877.

[8] [8] GHAFOORI N, BATILOV I, NAJIMI M. Influence of dispersion methods on sulfate resistance of nanosilica-contained mortars[J]. Journal of Materials in Civil Engineering, 2017, 29(7): 04017038.

[9] [9] DIAB A M, ELYAMANY H E, ABD ELMOATY A E M, et al. Effect of nanomaterials additives on performance of concrete resistance against magnesium sulfate and acids[J]. Construction and Building Materials, 2019, 210: 210-231.

[10] [10] HUANG Q, ZHU X H, ZHAO L, et al. Effect of nanosilica on sulfate resistance of cement mortar under partial immersion[J]. Construction and Building Materials, 2020, 231: 117180.

[11] [11] HUANG J J, WANG Z K, LI D S, et al. Effect of nano-SiO2/PVA fiber on sulfate resistance of cement mortar containing high-volume fly ash[J]. Nanomaterials, 2022, 12(3): 323.

[14] [14] REGALLA S S, SENTHIL KUMAR N. Effect of nano SiO2 on rheology, nucleation seeding, hydration mechanism, mechanical properties and microstructure amelioration of ultra-high-performance concrete[J]. Case Studies in Construction Materials, 2024, 20: e03147.

[15] [15] YANG L, ZHU Z D, ZHANG D W, et al. Influence mechanism of nano-SiO2 on geopolymer recycled concrete: change mechanism of the microstructure and the anti-carbonation mechanism[J]. Cement and Concrete Composites, 2024, 146: 105364.

[18] [18] CAI Y M, HOU P K, CHENG X, et al. The effects of nanoSiO2 on the properties of fresh and hardened cement-based materials through its dispersion with silica fume[J]. Construction and Building Materials, 2017, 148: 770-780.

[22] [22] HUANG Q, XIONG G Q, FANG Z, et al. Long-term performance and microstructural characteristics of cement mortars containing nano-SiO2 exposed to sodium sulfate attack[J]. Construction and Building Materials, 2023, 364: 130011.

[23] [23] ALY M, HASHMI M S J, OLABI A G, et al. Effect of colloidal nano-silica on the mechanical and physical behaviour of waste-glass cement mortar[J]. Materials & Design, 2012, 33: 127-135.

[24] [24] YU R, SPIESZ P, BROUWERS H J H. Effect of nano-silica on the hydration and microstructure development of ultra-high performance concrete (UHPC) with a low binder amount[J]. Construction and Building Materials, 2014, 65: 140-150.

[25] [25] HOU P K, KAWASHIMA S, KONG D Y, et al. Modification effects of colloidal nano-SiO2 on cement hydration and its gel property[J]. Composites Part B: Engineering, 2013, 45(1): 440-448.

[26] [26] YING J W, ZHOU B, XIAO J Z. Pore structure and chloride diffusivity of recycled aggregate concrete with nano-SiO2 and nano-TiO2[J]. Construction and Building Materials, 2017, 150: 49-55.

[27] [27] JI T. Preliminary study on the water permeability and microstructure of concrete incorporating nano-SiO2[J]. Cement and Concrete Research, 2005, 35(10): 1943-1947.