More Details

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

  1. Type N Hammer (Standard) – Used for normal concrete structures with a compressive strength range of 10 - 70 MPa.

  2. Type L Hammer (Low Impact) – Suitable for thin elements and light-weight concrete.

  3. Type M Hammer (Medium Impact) – Used for general-purpose concrete testing.

  4. Type P Hammer (High Impact) – Designed for mass concrete structures like dams and bridges.

Components of a Concrete Test Hammer

  1. Plunger – Pressed against the concrete surface to generate impact.

  2. Hammer Mass & Spring Mechanism – Controls the force of impact.

  3. Rebound Scale – Displays the rebound number (R-value).

  4. Housing with Dial Gauge or Digital Display – Shows the test results.

Working Principle

  • The hammer impacts the concrete surface with a standard force.

  • The rebound distance of the plunger is recorded as the Rebound Number (R-value).

  • A higher rebound value indicates higher concrete strength, and vice versa.

  • The compressive strength is estimated using calibration charts provided with the hammer.

Testing Procedure (IS: 13311 - Part 2)

1. Surface Preparation

  • Ensure the concrete surface is clean and dry.

  • Avoid testing on rough, porous, or uneven areas.

2. Performing the Test

  • Hold the hammer perpendicular to the test surface.

  • Press the plunger firmly against the concrete until the hammer releases an impact.

  • Note the rebound number (R-value) from the scale or display.

3. Taking Readings

  • Perform at least 10 readings in a test region.

  • Discard outliers and calculate the average rebound value.

4. Estimating Compressive Strength

  • 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.
🔹 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.
✅ Quality Control – Ensures uniformity in concrete production.
✅ Damage Detection – Helps assess deterioration, cracks, and carbonation.
✅ On-Site Testing – Provides quick, non-destructive strength estimates.