Quality Control, Testing, and Inspection
Quality control for dry-mix shotcrete verifies materials, placement, and in-place properties. Pre-placement checks include verifying mix components, equipment condition, air and water pressures, and substrate preparation. During placement, inspectors watch nozzle technique, water control, layer thickness, and rebound management. After placement, testing may include compressive strength from cores or test panels, thickness verification, bond or soundness checks, and visual inspection for voids, sand pockets, and delamination.
Because dry-mix water is added at the nozzle, in-place water content varies; test panels cast with the same technique and water setting are valuable references. Cores should be taken from representative locations, avoiding reinforcement and edges. Understand that test results depend on curing and sampling; a single poor result warrants investigation, not automatic rejection. Document water settings, ambient conditions, and any deviations.
Traps: assuming lab-mixed samples represent field placement; sampling only convenient locations; ignoring curing effects on test results; failing to record nozzle water settings; overlooking visual defects before coring.
Worked example / rule of thumb: cast test panels alongside production work using the same nozzleman and water setting, cure them under comparable conditions, and core them for strength. Pair test data with visual inspection and thickness checks so conclusions rest on multiple lines of evidence.