Proceq Original Schmidt Hammer Type L

The Schmidt Hammer is one of the oldest NDT methods in structural engineering and remains useful — but only when its limitations are explicitly understood. TRSC uses the Type L variant rather than the more common Type N because the lower impact energy is appropriate for the thin walls, heritage masonry, and sandstone facades that dominate our work. Three things govern reliable results: first, the surface must be smooth, dry, and on the body of the element being tested — readings on edges, corners, fresh chip-out areas, or carbonated zones are unreliable. We grind a small test patch (typically 80 mm × 80 mm) flat with a diamond wheel before testing, and we never test within 25 mm of an edge. Second, the rebound number is not strength — it correlates to surface hardness, which itself correlates to surface compressive strength via a calibration curve. The manufacturer base curve is a starting point; for any TRSC investigation that depends on quantitative strength values, we calibrate the Schmidt reading against extracted core compressive testing for the specific concrete in question. Without project-specific calibration, Schmidt-derived strength values carry ±20-30% uncertainty. Third, carbonated concrete reads systematically higher than uncarbonated concrete of the same actual strength. For pre-1960 reinforced concrete and any heritage masonry, we scrape away the carbonated surface zone before testing, or interpret readings with explicit awareness of the carbonation depth measured separately. The Type L Schmidt has been used by TRSC on the Victory Hotel sandstone investigation, the Prince Consort Hotel masonry capacity work, and as a screening tool prior to core extraction at Marina Mirage and 12 Creek Street.