Synthesis and effect of highly active nano-SiO2 on ion/water transmission property of cement-based materials

In recent years, due to superior performance of nano-SiO 2 , it is widely studied and applied in cement-based materials to improve mechanical properties and durability of the matrix. Nano-SiO 2 could be a potential surface-treatment agent, however, the activity of nano-SiO 2 determines surface modification effect. In this work, in order to obtain high activity nano-SiO 2 , three samples, with different sizes, surface hydroxyl groups , and viscosities , were synthesized via a so-gel method by adjusting the experimental parameters such as water dosage and reaction temperature. Water absorption rate and chloride ion penetration experiments were carried out to investigate ion/water transmission property of cement-based materials after surface treatment using nano-SiO 2 . S-20 sample dropped the water absorption rates by 28.8% and chloride penetration depths by 57.5%. The pozzolanic reaction and accelerating C 3 S hydration process were carried out to evaluate the activity of obtained nano-SiO 2 . The above results indicate S-20 sample shows the highest activity. The preparation method of high-activity nano-SiO 2 is provided to significantly improve surface quality of the cement paste matrix.