IS 516:2022 Part 5/Sec 3 is the Indian Standard (BIS) for methods of tests for strength of concrete - part 5: non-destructive testing of hardened concrete - section 3: rebound hammer. This code specifies the standard procedure for non-destructive testing of hardened concrete using a rebound hammer. Engineers use it to assess in-situ concrete uniformity, delineate zones of poor quality, and estimate relative compressive strength in existing structures.
Describes the procedure for assessing the surface hardness and estimating the strength of hardened concrete using a rebound hammer.
Quick Reference — IS 516 Part 5 Sec 3:2022 Cover Meter NDT
Cover-meter accuracy, detection range, calibration, bar-spacing limits and reporting.
| Reference | Value | Clause |
|---|
| Test covered | Cover (concrete cover) measurement using cover meter | Cl. 1 (Scope) |
| Principle | Electromagnetic induction — bar location & depth | Cl. 4 |
| Calibration — block / known cover | Manufacturer reference plate; verify before each project | Cl. 5.2 |
| Measurement accuracy — typical | ± 2 mm (within calibrated range) | Cl. 6 (Table) |
| Detection range — practical | 0–100 mm cover (some up to 180 mm) | Cl. 6 |
| Bar diameter — required input | Yes (improves cover accuracy) | Cl. 6.3 |
| Adjacent bar effect — min spacing | ≥ 100 mm clear (else readings affected) | Cl. 6.4 |
| Surface — preparation | Smooth; paint OK; large laitance to be removed | Cl. 6.2 |
| Grid — typical scan | 100 × 100 mm raster on critical members | Cl. 6.5 |
| Reporting | Cover, bar diameter, location plot | Cl. 7 |
| Half-cell potential — corrosion test (separate) | Refer Sec 4 / IS 13311 Pt 4 ref | |
| Cross-check with cores | Recommended in critical / disputed locations | Cl. 6.6 |
⚠ 2022 publication; some manufacturers' instruments exceed BIS-stated accuracy. Always validate with at least one core/chipping check.
Overview
- Status
- Current
- Usage level
- Frequently Used
- Domain
- Structural Engineering — Testing Methods and Quality Control
- Type
- Testing Method
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Practical Notes
! Rebound hammer readings are highly sensitive to surface conditions. Surface carbonation artificially inflates the rebound number, leading to an overestimation of strength.
! Do not take readings directly over reinforcing bars with shallow cover, as the steel will cause abnormally high rebound numbers.
! The rebound hammer provides only an approximate indication of strength. For structural assessment, it must always be correlated with drilled concrete core tests.
Frequently referenced clauses
concretehardened concrete
International Equivalents
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We're adding equivalent international standards for this code.
Key Values5
Quick Reference Values
Minimum readings per test area9 readings
Minimum distance between impact points20 mm
Minimum distance from edge of member20 mm
Minimum member thickness to avoid mass effect100 mm
Test area sizeApproximately 300 mm x 300 mm
Tables & Referenced Sections
Key Clauses
Clause 5 - Apparatus and Calibration
Clause 6 - Selection and Preparation of Test Area
Clause 7 - Procedure for taking Rebound Number
Clause 8 - Expression of Results
Frequently Asked Questions4
How many impact readings are required for a single test result?+
A minimum of 9 valid readings must be taken over the test area to calculate the median/mean rebound number.
What is the minimum distance allowed between two impact points?+
Impact points must be at least 20 mm apart and 20 mm away from any edge.
Can the rebound hammer be used for acceptance of new concrete?+
No, it is intended to check uniformity and relative strength, but cannot substitute standard cube tests for official acceptance without extensive correlation.
How often should the rebound hammer be calibrated?+
It should be checked against a standard steel calibration anvil before and after every test sequence to ensure consistent spring performance.
QA/QC Inspection Templates
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QA/QC templates coming soon for this code.