Shotcrete

Isolated Exposed Reinforcing Steel Encountered after Shotcrete Application

Isolated exposed reinforcement is not uncommon after finishing of the pool’s interior gunite or shotcrete surface. Exposed reinforcement is caused by the steel installer not maintaining the reinforcement within the anticipated limits of the final shotcrete or gunite finish surface. Exposed reinforcement can be encountered almost anywhere but is commonly found at outside corners, on the inside surfaces of tight radii such as circular spas and at bench/wall intersections. When less then minimum cover over the reinforcement is encountered, the gunite or shotcrete finishers will usually carve the concrete away from the exposed reinforcement leaving a small depression. Fortunately, isolated exposed reinforcement usually occurs at locations higher up the pool wall where the stresses in the reinforcing steel are low. For example, the stress in the reinforcement at 24 and 36 inches down from the bond beam is only 730 psi and 1820 psi respectively while the allowable stress is 20,000 psi. Therefore, it is our opinion that the removal of isolated exposed reinforcement will not be detrimental to the structural integrity of the swimming pool.

It is our recommendation that the exposed reinforcing steel be either hammered back to provide proper coverage or removed. In either case the exposed surface of the reinforcement must be sealed with a rust inhibiting coating. The depressions in the gunite surface should then be filled to present a uniform surface for plaster application.

Dry pack mortar (low water content) may be used for small repairs to minimize the potential for shrinkage cracking. Pre-packaged products such as Rapid-Set Mortar Mix, a low shrinkage, fast setting product formulated for repair applications, is ideal for minor repairs in swimming pool. When using pre-packaged products, it is critical that the manufacturers use limitations, mixing and placing instructions be explicitly followed.

When using Dry Pack Mortar or equivalent, the material should be applied over cement paste or another approved bonding agent, which has been brushed onto the saturated surface dry substrate (existing material) for absorption into the pore structure. The repair material shall be applied before the cement paste or other approved bonding agent “skins over” or starts its “setting stage”.