Rebound Hammer Test (Schmidt Hammer)

The rebound hammer test — also known as the Schmidt hammer test — is a rapid, non-destructive method for assessing the surface hardness of hardened concrete and estimating its compressive strength. A spring-loaded mass strikes the concrete surface through a plunger; the rebound distance is measured and converted to a rebound number, which correlates to compressive strength via calibration curves.

The rebound hammer is ideal for uniformity mapping across large structures, comparative assessment between concrete elements, and preliminary strength estimation when non-destructive assessment is required.

Test Standards We Follow

BS EN 12504-2

European/British standard for non-destructive determination of rebound number in concrete structures.

MS EN 12504-2

Malaysian Standard aligned with BS EN, formally recognised by JKR, CIDB, and Malaysian consulting engineers.

ASTM C805

US standard for the rebound number of hardened concrete — applied where projects reference American testing methods.

When Is Rebound Hammer Testing Used?

Uniformity assessment across large structures
Map surface hardness across walls, columns, slabs, and beams to identify areas of inconsistent strength.
Comparative strength evaluation between pours
Compare the relative strength of concrete from different pours or between structural elements.
Investigation of concrete suspected of being under-strength
Follow up on failed cube results with in-situ non-destructive assessment before deciding on further action.
Screening prior to more definitive tests
Identify areas requiring more detailed investigation via UPV or core extraction.
Assessment of existing buildings
Evaluate concrete condition before renovation, change of use, or structural modification.
Bridge and infrastructure condition monitoring
Periodic checks on bridges, viaducts, and other infrastructure to detect deterioration over time.
Forensic investigation following incidents
Assess concrete affected by fire, impact damage, or environmental exposure.

How the Test Works

Step 1 — Surface Preparation
The test surface is ground smooth using a carborundum stone over an area of approximately 150 by 150 millimetres to remove surface irregularities, plaster, or coatings.
Step 2 — Instrument Verification
The rebound hammer is verified against a calibration anvil before use to confirm consistent performance.
Step 3 — Position and Orientation
The hammer is held perpendicular to the test surface. Orientation (horizontal, vertical up, vertical down, angled) is recorded and applied to the correction factor.
Step 4 — Impact Readings
A minimum of 10 rebound readings are taken within the test area, with each impact point at least 25 millimetres from any edge or another impact point.
Step 5 — Data Processing
Outliers are discarded per the standard, and the mean rebound number is calculated for each test location.
Step 6 — Strength Estimation
The rebound number is converted to estimated compressive strength using the manufacturer’s calibration curve or, ideally, a site-specific correlation established from cores.

Why Foundtest for Rebound Hammer Testing?

Calibrated digital rebound hammers with traceable certificates
Experienced technicians who interpret results in engineering context, not just raw numbers
Field reports issued within 3 working days of testing
Recommended follow-up testing advised where readings warrant investigation
Combined packages available with UPV testing for enhanced reliability (SonReb method)
Full compliance with BS EN, MS EN, and ASTM standards

Frequently Asked Questions

Is the rebound hammer test destructive?

No. It is a fully non-destructive test that leaves only a very small mark on the concrete surface. It is safe to use on completed structures, finished surfaces, and heritage buildings without causing damage.

How accurate is the compressive strength estimate?

The rebound hammer gives an estimate typically within plus or minus 20 percent of true compressive strength when properly calibrated. For definitive strength values, we recommend following up with core testing on selected locations.

Can rebound hammer testing replace cube tests?

No. It is a complement, not a replacement. Cube tests remain the primary quality control method for concrete during construction. The rebound hammer is used for in-situ assessment of hardened concrete already in place.

How many readings do you take at each location?

A minimum of 10 rebound readings per test location, as required by BS EN 12504-2, with statistical processing to remove outliers and calculate a reliable mean rebound number.

Can you test old concrete structures?

Yes — this is one of the most common applications. We regularly test buildings 20 years old and older to assess concrete condition before renovation, adaptive reuse, or structural modification.

Book Rebound Hammer Testing

Contact Foundtest for on-site rebound hammer testing across Malaysia. Call +603-8051 5333, WhatsApp us, or use the contact form for a same-day quote.

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Rebound Hammer Test (Schmidt Hammer)

Test Standards We Follow

BS EN 12504-2

MS EN 12504-2

ASTM C805

When Is Rebound Hammer Testing Used?

Uniformity assessment across large structures

Comparative strength evaluation between pours

Investigation of concrete suspected of being under-strength

Screening prior to more definitive tests

Assessment of existing buildings

Bridge and infrastructure condition monitoring

Forensic investigation following incidents

How the Test Works

Step 1 — Surface Preparation

Step 2 — Instrument Verification

Step 3 — Position and Orientation

Step 4 — Impact Readings

Step 5 — Data Processing

Step 6 — Strength Estimation

Why Foundtest for Rebound Hammer Testing?

Calibrated digital rebound hammers with traceable certificates

Experienced technicians who interpret results in engineering context, not just raw numbers

Field reports issued within 3 working days of testing

Recommended follow-up testing advised where readings warrant investigation

Combined packages available with UPV testing for enhanced reliability (SonReb method)

Full compliance with BS EN, MS EN, and ASTM standards

Frequently Asked Questions

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