PoolQ What would be the right concrete mixture for a swimming pool? I found out that a few concrete plants have different mixes, so I wanted to know what would be the correct one.
There is no special requirement for shotcrete placement in pools. Basically, you are building a watertight structural concrete shell. Concrete should be a minimum 28-day compressive strength of 4000 psi (28 MPa). Most shotcrete uses a 3/8 in. (10 mm) maximum coarse aggregate size due to our small diameter delivery lines. The coarse aggregate (rock) being about half the weight of the sand content. We typically need a cement-rich paste so minimum cementitious content (cement, fly ash, slag) of 700 lb/yd3. We also need a low w/cm ratio for the ability to stack in the wall so maximum of 0.45, with most wet-mix concrete 0.42 or less. You may find our ASA Position Statements for our Pool and Recreational Committee helpful in providing more detail. Our current statements include:
- Compressive Strength Values of Pool Shotcrete
- Shotcrete Terminology
- Sustainability of Shotcrete in the Pool Industry
- Watertight Shotcrete for Swimming Pools
- Monolithic Shotcrete for Swimming Pools (No Cold Joints)
- Forming and Substrates in Pool Shotcrete
- Curing of Shotcrete for Swimming Pools
You can find the position statements freely available at shotcrete.org/products-services-information/resources/.
