Rebound Hammer Test

The Rebound Hammer Test is a Non-Destructive Test (NDT) used to determine the surface hardness and approximate compressive strength of concrete without damaging the structure.

Purpose of Rebound Hammer Test

· Estimate concrete strength

· Check uniformity of concrete

· Identify weak or damaged areas

· Quality control of concrete structures

Principle

· Higher rebound number indicates harder concrete

· Lower rebound number indicates weaker concrete

Test Procedure

· Clean the concrete surface

· Hold hammers perpendicular to the surface

· Press hammer until impact occurs

· Note rebound number

· Take minimum 10 readings

· Calculate average rebound value

Advantages

· Quick and easy test

· No damage to structure

· Portable equipment

· Useful for existing structures

Limitations

· Approximate strength only

· Surface condition affects results

· Not suitable for rough surfaces

Standard Codes

IS 13311 (Part 2) – Non-Destructive Testing of Concrete, ASTM C805

 

 

Typical Rebound Number Guide

Rebound Number	Concrete Quality
> 40	Very Good
30 – 40	Good
20 – 30	Fair
< 20	Poor

 

Demo Calculation of Rebound Hammer Test

The Rebound Hammer Test is a Non-Destructive Test (NDT) used to estimate the compressive strength and surface hardness of concrete.

Objective

To determine the approximate compressive strength of concrete using rebound numbers.

Example Calculation

Concrete Member: RCC Column

Reading No.	Rebound Number
1	32
2	35
3	34
4	33
5	36
6	31
7	34
8	35
9	33
10	34

Step 1: Calculate Average Rebound Number

Average Rebound Number = (32 + 35 + 34 + 33 + 36 + 31 + 34 + 35 + 33 + 34) / 10

Step 2: Solve

Average Rebound Number = 33.7

Step 3: Estimate Concrete Strength

Using the rebound hammer correlation chart:

Average Rebound Number = 34

Estimated Compressive Strength ≈ 28 MPa

Result Interpretation

Rebound Number	Concrete Quality
> 40	Very Good
30 – 40	Good
20 – 30	Fair
< 20	Poor

Final Result

Average Rebound Number = 33.7

Estimated Concrete Strength = 28 MPa

Concrete Quality = Good

Important Notes

· Minimum 10 readings should be taken

· Discard readings differing by more than ±20%

· Surface should be smooth and dry

· Do not test on cracked or honeycombed surfaces