Plastic shrinkage cracking properties of high-performance shotcrete with supplementary cementitious materials

Abstract

This article examines the characteristics of shotcrete from the standpoint of resistance to plastic shrinkage cracking. The effects of 2%, 3%, and 4% replacement with colloidal silica (CS) with a 10-nm particle size on the performance of shotcrete was examined, as were the effects of addition of supplementary cement materials in combination with CS, such as silica fume (SF) and ultra-fine fly ash (UFFA). Plastic cracking was examined from three perspectives: its effect on strength development (especially at the initial stage), assessment of plastic shrinkage in accordance with the ASTM C1579, and related issues of bleeding and evaporation. Compressive and flexural strength tests were conducted to gain an understanding of the processes involved, and the Intelligent Crack Viewer FCV-30 was used to estimate crack widths. The results show that the replacement with CS increases the compressive and flexural strength during hardening, which increases its resistance to tensile shrinkage stresses. The practical assessment of cracks showed that a significant reduction in the width of plastic shrinkage cracks was also achieved. The combination of 4% SF and 2% CS significantly reduced the risk of cracking and improved strength characteristics. The application of CS reduced the effect of 20% UFFA on plastic cracking.