Influence of Colloidal Silica and Silica Fume on the Rheology and Mechanical Properties of High-Performance Shotcrete

Abstract

Wet-mix shotcrete technology is widely used worldwide. One possible approach to developing this technology is the use of various admixtures to improve its pumpability and shootability. However, the commonly used slump test is insufficient to evaluate the capabilities of fresh shotcrete, because they do not assess the influence of multiple factors on its workability and placement properties. The purpose of this paper is to investigate and determine the effect of colloidal silica with a particle size of 10 nm (with 2%, 3%, and 4% replacement) on high-performance shotcrete from a rheological and mechanical perspective. In addition, to compare these indicators, silica fume is used with a 4% and 7% mixing rate. Rheological parameters such as torque viscosity and flow resistance of fresh concrete were evaluated using an ICAR rheometer, and the measured values were correlated with pumpability and shootability. The results of the study demonstrate that torque viscosity decreases and flow resistance increases with the increase in the percentage of colloidal silica. Similarly, silica fume increases flow resistance and reduces torque viscosity. These findings demonstrate the possibility of obtaining high-performance shotcrete with improved pumpability and shootability by employing more colloidal silica and silica fume. It was also established that these supplementary cement materials improve the strength and durability of shotcrete.