Shotcrete vs. gunite: what’s the difference?

Gunite (dry-mix): dry cement and sand are blown through a hose with compressed air, and the nozzle operator adds water at the tip as it is sprayed onto the steel. The operator controls the water-to-cement ratio by hand.

Shotcrete (wet-mix): concrete is batched at a plant, delivered by a ready-mix truck already mixed with water, then pumped and sprayed with air at the nozzle. The mix is set before it reaches the site.

• Strength: both can reach well over 4,000 psi. Quality depends on the mix, the nozzle work and compaction more than on the method.
• Consistency: wet-mix shotcrete arrives with a controlled water ratio. Gunite depends on the operator adjusting water by eye.
• Rebound and waste: gunite usually bounces off more material during spraying, which must be cleaned out and not reused.
• Scheduling: gunite can stop and start because the dry mix does not set until water is added. Shotcrete has to be placed within a set window after batching, so the crew has to keep pace.
• Feel and finish: once plastered or finished, the two shells look and feel the same.

• An engineered steel schedule with the right rebar size, spacing and clearance
• Proper shell thickness, especially on raised spas, infinity edges and walls
• Experienced nozzle work that fully encases the steel without voids
• Wet curing for the first week or more so the shell reaches full strength
• In the Keys, a dry, stable excavation in coral rock, which often means dewatering

Shotcrete’s plant-controlled mix gives us a consistent shell from the first truck to the last, which suits the raised spas, sun shelves and infinity edges our clients ask for. It also fits our 4–6 week build schedule. Learn more on our concrete pools page or see what a pool costs in the Keys.