Frost resistance of concrete mixed with nano-silica in severely cold regions

Currently, the lowest temperature for the conventional freeze-thaw (FT) cycles tests of concrete are usually not lower than −20 °C. However, for concrete structures in severely cold regions, the winter temperature is below −20 °C. Compared with the conventional FT cycle test condition, concrete in severely cold regions is bound to suffer more serious FT deterioration, and it is necessary to improve the frost resistance of concrete in severely cold regions. To obtain the influence effect of nano-silica (NS) on the frost resistance of concrete in severely cold regions, a series of multi-scale tests were performed on the concrete added with 2% NS under the FT cycles of −40 °C ∼ +5 °C, as well as the concrete without NS (as a control). The results show that 2% NS can enhance the frost resistance of the concrete in severely cold regions. Namely, when the FT cycle number is the same, the performances of the concrete added with 2% NS are better than those without NS. Meanwhile, the performances of the concrete added with 2% NS after 200 FT cycles are still better than those without NS after only 100 FT cycles.