New Testing Procedure for Shrinkage Cracking of Fiber-Reinforced Shotcrete

Abstract

Plain shotcrete and fiber-reinforced shotcrete (FRS) are commonly employed to produce layers or linings with large surface/volume ratios. Restrained shrinkage cracking is hence an important concern from both structural and durability aspects. In this investigation, a new testing procedure is adopted to study the shrinkage cracking behavior for plain shotcrete and four different types of FRS (polypropylene, steel, polyvinylalcohol, and hybrid). To introduce shrinkage restraint, specimens cut from a shotcrete panel are bonded to a steel fixture. By measuring the shrinkage strain of the restrained specimen at different times, the occurrence of cracking can be easily observed from a sudden “jump” in the strain values. To find the actual strain induced on the restrained specimen, unrestrained members were also monitored to obtain the free shrinkage. For various plain and reinforced shotcrete mixes, the induced strain when cracking occurs is found to follow an order that is generally consistent with physical intuition.