These mixes are cement rich, generally in the 6 ½ sx to 8 sx range with up to an 80%-20% blend of Building Sand and Pea Gravel. Ultimate compressive strengths of 2000 psi to 6000 psi are typical. The delivered slump averages about 2 inches, in order for the mix to virtually stand on its own against a one sided forming system or earthen wall having steel reinforcement. Shotcrete and Gunite are air-placed concrete mixes which incorporate the use of a grout pump that introduces compressed air at the discharge nozzle. Shotcrete is a structural mix suitable for soil stabilization all the way to finished in-place load bearing walls. These structural applications (one sided placement or slip form) must be executed by a City of Seattle certified contractor. Gunite, on the other hand, is considered to be less of a structural mix and is used in soil stabilization projects or more commonly for “in ground” concrete pools.