PoolQ The Park District Department of our city is in the process of designing a new swimming pool. One of the prospective bidders made a presentation in which they said they would use shotcrete instead of conventional cast in place concrete. Their design is to use 6 in.-thick walls instead of the 12 in.-thick walls as proposed for the cast in place design. They claim that 6 in. of shotcrete is as strong as 12 in. of formed concrete. Is this a true statement?
If this statement was true, there would be a lot more shotcrete projects! The truth is that shotcrete is a method of concrete placement, not a special material. The materials, mix designs, and mix proportions may vary between the shotcrete method and the conventional concrete form and pour method, but the thickness and reinforcing of the structure will be very similar.
There is a subtle difference between the two methods that might affect thickness requirements. Shotcrete is generally placed directly onto the undisturbed soil, joining with the soil to provide the shell for the pool. To use the form and pour method, over-excavation would be required to accommodate two-sided forming. The walls would then have to withstand the forces of backfilling. This may result in a thicker wall requirement. The final decision regarding wall thickness, however, should be made by a structural engineer.
Shotcrete is widely used for swimming pool construction. In some areas it is virtually the only method used. Successful shotcrete swimming pool construction is a result of having an appropriate design, selecting a qualified contractor with certified nozzlemen, selecting appropriate materials and shotcrete mixture design, and following industry recommendations for placing, finishing, and curing.
