Experimental study of shotcrete and concrete strength development in a hot spring environment

• Weakly base hot spring water at 40 °C does not affect strength development for shotcrete and concrete.
• Curing in hot spring at 40 °C may benefit early stage strength development and subsequent integrity.
• Chloride and sulfate ions in hot spring do not enhance the alkali–aggregate or carbonate reaction.

To determine the influence of hot spring water on mechanical characteristics of tunnel supports made from Portland cement, this study investigates strength development and associated temporal variations of shotcrete and concrete specimens cast in situ and cured in water from a hot spring. Experimental results reveal that weakly-base hot spring water with a curing temperature of 40 °C does not adversely affect strength development for shotcrete and concrete; however, the hot spring curing environment may benefit early stage strength development and subsequent integrity. Chloride and sulfate ions in hot spring water do not enhance the alkali–aggregate or alkali–carbonate reaction significantly. Concrete specimens with high uniaxial compressive strength have high surface hardness, high electrical resistance and low permeability, implying excellent short-term durability.