Abstract

The effect of nano-silica-containing alkali-free accelerator and ordinary alkali-free accelerator on the durability of C30 shotcrete was investigated by means of seepage resistance tests and frost resistance tests. The results show that under the same conditions, the C30 shotcrete with nanosilica-containing alkali-free accelerator has a lower electrical flux and a greater impermeability rating than P10. The C30 shotcrete with nano-silica-containing alkali-free accelerator maintains a mass loss rate of about 0.4% after 200 freeze-thaw cycles, a 10.5% decrease in relative dynamic modulus of elasticity, a compressive strength loss rate of less than 20%, the bubble spacing coefficient and the average bubble diameter increased by 20.9% and 60.5% respectively, showing good frost resistance performance. This indicates that alkali-free accelerator containing nano-silica can improve the durability of shotcrete. In addition, a comparison was also made between ordinary accelerator shotcrete with nano-silica, and when 5% nano-silica was added, the properties of shotcrete were comparable to those of 2% nano-silica alkali-free accelerator shotcrete.