Porosity, pore size distribution and chloride permeability of shotcrete modified with nano particles at early age

Abstract

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 SiO₂, CaCO₃ and Al₂O₃ particles on the early-age porosity, pore size distribution, compressive strength and chloride permeability of shotcrete were investigated.Test results indicated that nano SiO₂ particles significantly increased the compressive strength and chloride penetration resistance; nano Al₂O₃ and CaCO₃ particles had slight enhancing effect on the compressive strength; nano CaCO₃ particles were most effective in promoting the chloride penetration resistance of shotcrete. As a conclusion, nano SiO₂ particles were recommended when both early age compressive strength and chloride penetration resistance were crucial, and nano CaCO₃ particles were recommended when only chloride penetration resistance was concerned for their high cost-effectiveness.

Keywords

shotcrete / nanoparticles / chloride penetration resistance / compressive strength / porosity

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