SV Technocrats India’s Concrete Test Hammer, also known as a Rebound Hammer or Schmidt Hammer, is a non-destructive testing (NDT) device used to measure the surface hardness and estimated compressive strength of concrete. It is designed as per IS: 13311 (Part 2), ASTM C805, and BS 1881-202.
Types of Concrete Test Hammers
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Type N Hammer (Standard) – Used for normal concrete structures with a compressive strength range of 10 - 70 MPa.
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Type L Hammer (Low Impact) – Suitable for thin elements and light-weight concrete.
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Type M Hammer (Medium Impact) – Used for general-purpose concrete testing.
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Type P Hammer (High Impact) – Designed for mass concrete structures like dams and bridges.
Components of a Concrete Test Hammer
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Plunger – Pressed against the concrete surface to generate impact.
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Hammer Mass & Spring Mechanism – Controls the force of impact.
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Rebound Scale – Displays the rebound number (R-value).
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Housing with Dial Gauge or Digital Display – Shows the test results.
Working Principle
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The hammer impacts the concrete surface with a standard force.
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The rebound distance of the plunger is recorded as the Rebound Number (R-value).
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A higher rebound value indicates higher concrete strength, and vice versa.
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The compressive strength is estimated using calibration charts provided with the hammer.
Testing Procedure (IS: 13311 - Part 2)
1. Surface Preparation
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Ensure the concrete surface is clean and dry.
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Avoid testing on rough, porous, or uneven areas.
2. Performing the Test
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Hold the hammer perpendicular to the test surface.
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Press the plunger firmly against the concrete until the hammer releases an impact.
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Note the rebound number (R-value) from the scale or display.
3. Taking Readings
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Perform at least 10 readings in a test region.
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Discard outliers and calculate the average rebound value.
4. Estimating Compressive Strength
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Use the manufacturer’s calibration chart to convert the R-value into compressive strength (MPa or N/mm²).
Factors Affecting Rebound Hammer Results
🔹 Surface Condition – Smooth surfaces yield
higher rebound values.
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Moisture Content – Wet concrete gives
lower readings.
🔹 Carbonation Effect –
Can artificially increase rebound values.
🔹
Aggregate Type – Harder aggregates
increase rebound readings.
Applications of Concrete Test Hammer
✅ Structural Assessment – Evaluates
concrete strength in buildings, bridges, and pavements.
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Quality Control – Ensures
uniformity in concrete production.
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Damage Detection – Helps assess
deterioration, cracks, and carbonation.
✅
On-Site Testing – Provides
quick, non-destructive strength estimates.
