PoolQ I have a question regarding shotcrete pools. Does the ASA have a position on how to detail reinforcement at bulky elements that are shot interior to the main pool shell? This would typically involve stairs or large stoops. I notice a lot of contractors shoot these as unreinforced bulk elements, but this practice appears to promote cracking at the face of the pool shell. I’m only asking because I saw a few of these this past summer.
Shotcrete is a placement method for concrete. Thus, any concrete structure using shotcrete placement should be designed using appropriate concrete design codes and standards. ASA does not have a published position on reinforcement of these types of pool elements though we are in the midst of developing one. As most concrete experiences drying shrinkage and associated cracking, most designers would include some level of reinforcement in these types of sections to control tensile stresses from shrinkage and temperature changes creating volume change in the concrete. ACI 350 (Code Requirements for Environmental Engineering Concrete Structures) is the ACI Code that deals with concrete liquid-containing structures with provisions specifically for providing liquid tightness and durability in continuously wet environments. The ACI 350 Code requires up to 0.5% reinforcement for shrinkage and temperature stresses. ACI 318 is the Concrete Code for Structures and requires 0.18% minimum reinforcement for shrinkage and temperature. Designers may choose to use the lower ACI 318 value since they consider the benches and steps not part of the water retaining pool shell. Other designers would consider the higher ACI 350 values as they are interested in better crack control. Overall, having a substantially unreinforced thickness of concrete would lead to more cracking that would be problematic in the pool.
