digital schmidt hammer

Digital Schmidt Hammer for Concrete (RH225-B Model)

The RH225-B digital Schmidt hammer, manufactured by LANGRY (Singapore), is a widely used non-destructive testing (NDT) instrument for concrete evaluation. This device is designed to estimate the compressive strength of concrete based on surface hardness measurements. By measuring the rebound value of an impact applied to the concrete surface, it provides valuable information about the quality and uniformity of concrete, and is extensively used in construction projects, quality control, and structural assessment.

Technical Specifications of the RH225-B Digital Schmidt Hammer (LANGRY)

• Equipped with electromagnetic sensor technology that does not interfere with rebound values, ensuring higher accuracy and longer service life

• Robust design resistant to light and dust

• Internal memory capable of storing up to 1000 data points across 100 different test areas

• Standard impact energy: 2.207 Joules

• Rechargeable lithium battery with 3200 mAh capacity

• Elastic resistance spring with stiffness of 785 N/m and spring extension length of 75 mm

• Calibration value on anvil: 80

• Built-in Bluetooth chip for connection to various printers

• Integrated online software system for automatic rebound data transfer

• Internal gyroscope for impact direction correction

• Supplied with silicone grip handle, complete maintenance kit, dedicated carrying case, and grinding stone

Operating Principle of the Schmidt Hammer (Rebound Hammer)

The Schmidt hammer operates by measuring the rebound energy of a spring-driven mass impacting the concrete surface. A piston with a defined energy strikes the concrete, and the amount of rebound—directly related to surface hardness—is measured and displayed as the Rebound Number (R-Value).

Denser and harder concrete results in a higher rebound value. Using standard calibration curves and charts, the rebound number can be converted into an estimated compressive strength of concrete, typically expressed in MPa or N/mm².

Test Procedure Using the Digital Schmidt Hammer

Before testing, the concrete surface must be smooth, clean, and free of paint, coatings, or loose particles. The device is then placed perpendicular to the concrete surface. Upon applying pressure, the impact is automatically released and the rebound value is displayed digitally.

According to international standards, at least 10 to 12 impacts should be performed in each test area with adequate spacing. Invalid readings are discarded, and the average of the remaining values is reported as the final test result.

Main Applications of the Digital Schmidt Hammer

• Non-destructive estimation of concrete compressive strength

• Quality control of concrete in construction projects

• Evaluation of concrete uniformity in existing structures

• Condition assessment of bridges, tunnels, and buildings

• Use in quality control laboratories and construction sites

Key Advantages of the RH225-B Digital Schmidt Hammer

• Completely non-destructive testing without damage to structures

• Digital display of rebound number and estimated compressive strength

• High accuracy and repeatability

• Data storage and transfer capability

• Reduced human error compared to analog models

• Automatic correction for impact direction (horizontal, vertical upward, vertical downward)

Limitations and Important Notes

• Test results depend on surface condition, moisture content, and age of concrete

• Suitable for preliminary strength estimation, not a replacement for destructive testing

• For higher accuracy, results should be correlated with core test data

• Periodic calibration using a standard anvil is essential to maintain accuracy