Schmidt Hammer Test (Rebound Hammer Test) for Concrete

Schmidt Hammer Test (Rebound Hammer Test) for Concrete

What is the Schmidt Hammer Test?
The Schmidt Hammer Test, also known as the Rebound Hammer Test, is a non-destructive testing (NDT) method used to assess the surface hardness of concrete and to estimate its compressive strength. The test was developed by Ernst Schmidt in the 1940s and is widely used for quality control and structural evaluation.

Principle & Test Method
Principle:  
The Schmidt hammer consists of a spring-loaded mass that, when released, strikes the concrete surface. The degree to which the mass rebounds is measured by a sliding indicator. The rebound value correlates with the surface hardness and, indirectly, to the compressive strength of concrete.
Operation Modes:  
Normal (horizontal)  
Upward (vertical upwards)  
Downward (vertical downwards)

Types of Data Provided
Rebound Value (R-value): Immediate output from the hammer, indicating surface hardness.
Estimated Compressive Strength: Using calibration curves or correlation charts.
Concrete Uniformity: Comparison of rebound values at different positions.
Detection of Surface Defects: Identification of weak zones, honeycombing, or low-quality areas.
Quality Control: Assessment of homogeneity between different lots or pours.

Standard Testing Procedure
Surface Preparation:  
Select clean, smooth, dry concrete spots.
Grind and prepare if necessary for rough or uneven surfaces.
Test Execution:  
Hold the hammer perpendicular to the surface and press until the hammer impacts.
Record the rebound value indicated on the scale.
Perform at least 10-12 readings in a single test area (per international guidelines).
Data Handling:  
Discard outliers (very high/low readings).
Calculate the average rebound value.
Use manufacturer’s correlation chart to estimate compressive strength.
Documentation:  
Record test location, concrete orientation, surface condition, and hammer type.

International Standards
ASTM C805 / C805M: “Standard Test Method for Rebound Number of Hardened Concrete”
EN 12504-2: “Testing concrete - Non-destructive testing - Determination of rebound number”
IS 13311 (Part 2)
BS 1881: Part 202
ACI 228.1R: In-place Methods to Estimate Concrete Strength

Advantages
Non-destructive: No sample removal or damage to structure.
Portable & Quick: Lightweight, easy to use virtually anywhere.
Immediate Results: Direct readings enable on-site decisions.
Economical: Low-cost compared to core drilling or laboratory tests.
Repeatable: Multiple tests in short time for quality control mapping.

Applications
Quality control at construction sites  
Assessing compressive strength of existing structures  
Mapping uniformity of concrete within members  
Identifying poor-quality or deteriorated zones  
Comparative evaluation between different batches/locations  
Pre-selection of areas for further detailed testing (coring, UPV, etc.)

For specialized testing equipment, procedures, calibration, and technical support in Iran:  
Clinic Beton Iran Group (RBS-CONTECH)  
Website: https://www.clinicbeton.com  
International: https://www.rbs-contech.com  
Email: clinicbeton.com@gmail.com  
Tel: +98 21 88070173, +98 21 88584906  
Mobile: +98 9102333497, +98 9120916271, +98 9120916272

 

Schmidt Hammer Test (Rebound Hammer Test) for Concrete

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