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Nano particles have been found to be effective in enhancing many properties of regular concretes. However, there is little information on the effect of nano particles on shotcrete. In fact, if similar positive effect of nano particles can also appear in shotcrete, they will greatly benefit the wide application of shotcrete in more and more repair and strengthening of structures in civil engineering, especially in corrosive environments. In this study, through experiments on 70 specimens, the effects of nano SiO_2, CaCO_3 and Al_2O_3 particles on the early-age porosity, pore size distribution, compressive strength and chloride permeability of shotcrete were investigated.Test results indicated that nano SiO_2 particles significantly increased the compressive strength and chloride penetration resistance; nano Al_2O_3 and CaCO_3 particles had slight enhancing effect on the compressive strength; nano CaCO_3 particles were most effective in promoting the chloride penetration resistance of shotcrete. As a conclusion, nano SiO_2 particles were recommended when both early age compressive strength and chloride penetration resistance were crucial, and nano CaCO_3 particles were recommended when only chloride penetration resistance was concerned for their high cost-effectiveness.
However, there is little information on the effect of nano particles on shotcrete. In fact, if similar positive effect of nano particles can also appear in shotcrete, they will greatly benefit the wide application of shotcrete in more and more repair and strengthening of structures in civil engineering, especially in corrosive environments. In this study, through experiments on 70 specimens, the effects of nano SiO 2, CaCO 3 and Al 2 O 3 particles on the early-age porosity , pore size distribution, compressive strength and chloride permeability of shotcrete were tested. Test results indicated that nano SiO 2 particles significantly increased the compressive strength and chloride penetration resistance; nano Al 2 O 3 and CaCO 3 particles had slight enhancing effect on the compressive strength; nano CaCO 3 particles were most effective in promoting the chloride penetration resistance of sh As a conclusion, nano SiO 2 particles were recommended when both early age compressive strength and chloride penetration resistance were crucial, and nano CaCO 3 particles were recommended when only chloride penetration resistance was concerned for their high cost-effectiveness.