Schmidt Rebound Hardness of Rock(ISRM Suggested Method)
Schmidt hammer rebound testing of rock outcrops, cores and blocks per the ISRM Suggested Method — a rapid, non-destructive strength index correlated to UCS and joint-wall strength.
What is the Schmidt Rebound Hardness Test of Rock?
The Schmidt hammer — familiar from concrete testing — is equally established on rock: the rebound value (R) of a calibrated hammer correlates with the compressive strength of the rock surface, and is the standard field index for joint-wall compressive strength (JCS) in the Barton-Bandis shear criterion. On rock, Indian practice follows the ISRM Suggested Method (there is no dedicated IS code for Schmidt testing on rock; IS 13311 Part 2 covers concrete), using L-type or N-type hammers with orientation corrections.
Global Lab performs Schmidt testing on outcrops, block samples and cores held in the standard cradle — applying the ISRM data-reduction (discarding outliers, averaging upper readings), orientation correction, and UCS correlation via the hammer's calibration curves with density input.
How the Schmidt Rebound Hardness of Rock is Conducted
- 1
Surface / Specimen Preparation
Test surfaces are cleaned and smoothed; cores are clamped in the standard steel cradle; weathered coatings are noted. - 2
Hammer Verification
The hammer is checked on the calibration anvil before and after each test series. - 3
Rebound Readings
The prescribed number of impacts are taken at separated points; orientation (horizontal/vertical/inclined) is recorded per reading. - 4
ISRM Data Reduction
Readings are reduced per the ISRM procedure with orientation correction applied. - 5
Correlation & Reporting
Corrected R-values, estimated UCS/JCS with the correlation basis, and location maps are issued via Autovity QLMS.
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| ISRM SM | ISRM Suggested Method for Determination of the Schmidt Hammer Rebound Hardness | Test Method | International |
| IS 13311 (Pt 2):1992 | Non-Destructive Testing of Concrete — Rebound Hammer (Reaffirmed) | Concrete Analogue (Reference) | Indian Standard |