Schmidt Hammer Testing

The Schmidt rebound hammer is a portable non-destructive testing instrument that measures the surface hardness of concrete by firing a spring-loaded mass against the surface and recording the rebound distance. The rebound number provides an indication of near-surface concrete quality and, through established correlations, an estimate of compressive strength, though TRSC treats rebound hammer results as indicative rather than definitive for strength assessment.

The primary value of Schmidt hammer testing in TRSC investigations is comparative rather than absolute. By systematically testing across a structure, areas of relatively lower surface hardness, indicating potentially weaker, deteriorated, or fire-damaged concrete, can be quickly identified and targeted for more detailed investigation. This screening function makes the Schmidt hammer an efficient first-pass tool for identifying zones of concern across large structures.

Schmidt hammer testing is rapid (approximately 12 impacts per test location, taking under one minute), portable, and requires no power supply or consumables. It is the fastest way to obtain an in-situ quality indication across a large number of locations. TRSC typically deploys Schmidt hammer testing alongside GPR and UPV as part of an integrated non-destructive testing programme, with each technology providing different but complementary information about the concrete condition.

For strength assessment, TRSC does not rely on rebound hammer results alone. Rebound number is influenced by surface moisture, carbonation, aggregate type, surface texture, and the age of the concrete, all of which affect the rebound-to-strength correlation. Where compressive strength data is required for structural calculations, TRSC extracts cores and submits them for NATA-certified laboratory testing. Schmidt hammer data is used to assess whether core results are representative of the broader structure.