Inspection, Testing, and Quality Control
Inspection and testing verify that shotcrete meets thickness, strength, and quality requirements. Candidates should know pre-construction testing (often a test panel shot by the production nozzleman under site conditions) and production testing. Common field tests include compressive strength (cores or test panels), thickness (cores, probes, or pre-installed depth gauges), and bond or in-place density checks. Test panels are typically shot in a manner simulating field conditions, cured, and cored for strength. Acceptance criteria and sampling frequency come from the project specification and referenced standards.
Traps: questions may confuse test-panel results with in-place results, or assume a single core represents a whole area. Also, dry-mix strength depends on nozzleman water control, so cores must be taken from properly representative locations. Thickness is often measured by coring or by shooting into a depth gauge; some specifications allow probing fresh shotcrete. Air content and fiber content may be verified from fresh or hardened samples depending on method. Documentation-batch records, placement records, test reports-is part of QC.
Rule of thumb: for strength acceptance, cores are typically taken from test panels (or in-place per specification) and tested after curing; a common practice is to require the average of cores to meet the specified strength with no individual result falling below a defined fraction of it-always confirm the exact criterion in the project specification.