Effects of admixtures on the rheological properties of high-performance wet-mix shotcrete mixtures

• Effects of various admixtures on the rheological properties of HPWMS were examined.
• Rheological properties such as yield stress and plastic viscosity were measured using IBB rheometer.
• The measured rheological properties were correlated to shootability and pumpability.
• Silica fume is the most effective admixture for enhancing the rheological properties of HPWMS.

This study investigates the effects of various admixtures on the rheological properties of high-performance wet-mix shotcrete (HPWMS) in an attempt to resolve practical issues faced in conventional wet-mix shotcrete processing. The admixtures used in this study were silica fume, air-entraining agent (AEA), superplasticizer, synthetic fiber, powdered polymer, and a viscosity agent. Representative rheological properties such as yield stress and plastic viscosity were measured using an IBB rheometer to evaluate the pumpability and shootability of HPWMS with varying admixture types and contents. The results demonstrated that the use of AEA tended to reduce both flow resistance and torque viscosity of HPWMS almost proportionally. A superplasticizer had a relatively greater impact on the flow resistance rather than torque viscosity. Also, it was observed that silica fume led to a remarkable increase in flow resistance while it slightly reduced torque viscosity. This behavior trend indicates that silica fume is quite effective in enhancing the rheological properties of HPWMS, particularly in terms of shootability and pumpability.