Evaluation of Early-Age Volume Changes of Shotcrete Using Ring Specimens

Abstract

In this study, both free and restrained shrinkage tests were performed to derive the total tensile strain behavior (i.e., creep effect) of wet-mix and dry-mix shotcretes. A simple analysis procedure is presented to quantify the tensile creep properties of shotcrete using results obtained from standard ring tests and mechanical property tests. The results showed that the rings dried along the axial direction had higher total tensile strain properties compared with those dried along the radial direction. The results further showed that coarse aggregate content of shotcrete affects the total tensile strain properties. Similarly, adding silica fume, fly ash, polymer, shrinkage-reducing admixture (SRA), and crack-reducing admixture (CRA) reduces the total tensile strain properties of shotcrete. However, the decrease observed when using SRA and CRA does not increase the risk of early-age cracking because shrinkage is also reduced proportionally. Thus, a higher total tensile strain capacity is only beneficial in reducing cracking if it does not cause a proportional increase in shrinkage. Overall, the analysis indicates that the effect of creep is a crucial factor in the evaluating of the risk and sensitivity to cracking of shotcrete.