Micro and Nano-Silica Additions to Optimize the Compressive Strength of Shotcrete

The reinforcement of excavated tunnels is of utmost importance for worker safety and operational efficiency in underground mining. Shotcrete significantly helps with both, and while many additions with sustainable and pozzolanic properties have been evaluated, few studies have established the upper strength limits and guidelines for the practice. This study seeks to maximize the compressive strength of shotcrete through an optimized formula with micro and nano silica additions. Three dosage combinations across four different water-cement mixtures were tested, with results presenting a compressive strength at a .45 water-cement ratio of 64.9 MPa, a 72% increase over the control. The greatest strength result was found at a .30 water-cement ratio and measured 106.7 MPa. These results present some of the highest documented compressive strength values for their respective water-cement ratios. They contribute shotcrete formulas to help the mining industry improve their underground safety structures and maintain operational efficiency.