Crack suppression
Due to high chloride content, water that reaches the steel reinforcement in the concrete can compromise the integrity of the structure. A waterproofing system with a high chemical chloride resistance and hairline crack bridging capabilities should be co-ordinated with the design-construction team to ensure consideration of essential details, penetrations/tie-ins, and separations.
Design professionals, architects, and engineers should also collaborate in the placement and specification of the expansion, control, isolation, and construction joints. This will contribute to crack suppression, ensure watertightness, and serve as an artistic expression to the finish surfaces.
An important addition to a well-thought-out waterproofing system is the design and installation of waterstops within the concrete pool shell. Waterstops help obstruct the incidental passage of water through concrete joints. They should be placed systematically between the vertical and horizontal structural elements and should be able to withstand a chemically aggressive environment.
Admixtures can also be used to improve durability performance. They waterproof the concrete by growing a non-soluble crystalline structure within its pores and capillary paths. This process helps seal hairline cracks, which contributes to watertightness.
During the early planning stages, the concrete mix design should be co-ordinated with an admixture manufacturer’s representative to ensure proper dosage and strength. To avoid underdosage, it is recommended to specify the minimum percentage by weight of cementitious material requirements to meet its high-performance standards.
The modified concrete will be treated as typical concrete, meaning there are no differences when applying decorative finishes or additional waterproofing tie-ins. However, the installer of the surface-applied material is responsible for taking the necessary measures to ensure compatibility and bond to the treated concrete.
While industry standards recognize reinforced concrete structures will have cracks to some extent, the pool’s concrete structure requires an approach that is more stringent and limits cracking.
Adding to the complexity of the engineering design, placement above a parking garage or unoccupied space limits the possibility of uniform placement of vertical structural supports. The spacing and frequency of these supports is ideally engineered to avoid deflections that would contribute to the cracking of the pool’s concrete shell structure or the finishes above. Spans exceeding safety guidelines put the pool structure at risk and could lead to costly repairs and extensive service interruptions.
While engineering codes and guidelines have provisions for complexity of design, non-uniform spans, and other challenges, they only address the structure’s immediate integrity—not its longevity.
Implementing additional measures during the design and schematic phases could help reduce deflections. For example, early co-ordination between the plumbing and structural engineer could reduce the number of penetrations (and those abandoned) and help with reducing overall congestion. The routing of plumbing, service lines, and pool equipment during design would lend to a shell structure that could further resist deflections and unanticipated stresses.
