This question should be addressed by a qualified engineer with experience in designing swimming pools and well-versed in shotcrete technology. Shotcrete is a method of placing concrete and the parameters that work for concrete cover work for shotcrete.
Good practices for placing shotcrete or concrete include:
- Predampening the soil that the concrete/shotcrete is placed against;
- Ensuring that the reinforcing bar temperature is not too high; and
- Early curing of the shotcrete surface and maintenance of curing for the specified duration. If no duration is specified, a 7-day wet cure is recommended.
Using fibers in the shotcrete/concrete can also help control surface early-age plastic shrinkage cracking.