Shrinkage performance of concrete for shotcrete use restrained by rock in hot and dry tunnel environment

The shotcrete shrinks greatly in the hot and dry environments, and the shotcrete is easy to crack or even debond under the restraint of the surrounding rock. In this context, a concrete-rock restrained shrinkage test device is used to study the shrinkage performance of concrete in the hot and dry environments of 80 degrees C, and the inhibitory effect of steel fiber and shrinkage reducing admixture on concrete shrinkage is explored. A concrete-rock restrained shrinkage mechanics model is established to calculate the interfacial restraint force and the distribution of stress and strain on the concrete section. The results show that the concrete expands at the initial stage under hot and dry environments, but the shrinkage of the concrete increases rapidly with the increase of age, and the growth rate slows down after a certain age and finally stabilizes. With the increase of the distance to the bonding surface, the shrinkage deformation of concrete increase continuously, and the stress distribution transitions from the tensile stress zone to compressive stress zone. The end-hook steel fiber and shrinkage reducing admixture can significantly reduce the shrinkage deformation and interfacial restraint force of concrete.

Automated summary

This study uses a concrete-rock restrained shrinkage test device to investigate the shrinkage performance of concrete in hot and dry environments, and explores the inhibitory effect of steel fiber and shrinkage reducing admixture on concrete shrinkage. The results show that concrete expands initially under hot and dry environments, but the shrinkage rate increases rapidly with age, slows down after a certain period, and eventually stabilizes.