Effect of unidirectional temperature conduction on the strength evolution of shotcrete in a high geothermal environment.

The high geothermal environment causes a temperature gradient inside shotcrete, which affects the development of its mechanical strength. This research investigated the strength evolution of shotcrete in simulated high geothermal environment by applying a unidirectional heat source. The influence of temperature gradient on the pore structure, morphology, phase composition, and hydration degree of shotcrete was also studied. It was found that the early strength of shotcrete was improved but that the later strength was reduced in the high geothermal environment. It was attributed to the increase in harmful porosity and total porosity of the concrete caused by the high-temperature curing. Cracks and pores can be observed in the microstructure near the heat source region. Besides, the ettringite content in shotcrete was lower than that under standard curing environment and presented gradient distribution in the direction of the temperature gradient. [ABSTRACT FROM AUTHOR]