Surface preparation is a critical operation. The substrate must be prepared properly. All deteriorated concrete must be removed. This is generally accomplished with light-duty chipping hammers, scarifiers, or scabblers. The remaining concrete is then sandblasted or water-blasted to remove the concrete “bruised” by the initial removal operation.

Shotcrete is concrete; it’s just the method of application that’s different. A shotcrete mixture likely would exceed the compressive strength of most mixtures used for placed walls because the application of shotcrete requires a much lower water-cementitious material ratio than commonly found in wall mixtures.

The proper placement is the most important element in achieving good shotcrete results. Most defects that occur in shotcrete are due to poor placement. Shotcrete’s success depends largely on the skill and actions of the nozzleman. The nozzleman’s goal is to achieve adequate compaction and good encasement of the reinforcement (if present) with no entrapped rebound or hardened overspray.