SCOPE: Compressive strength of concrete is very important criteria which can be easily computed by the Rebound Hammer .The rebound hammer is a nondestructive testing apparatus, whereby the rebound of the spring driven mass is measured after its impact with concrete surface. The output of the rebound hammer is referred to as rebound number and are correlated with surface hardness of concrete.
- RERFERENCE IS CODE: IS 516 (Part 5/Sec 4) : 2020
a. For testing, smooth, clean and dry surface is to be selected. If loosely adhering scale is present, this should be rubbed off with a grinding wheel or stone. Rough surfaces resulting from incomplete compaction, loss of grout, spalled or tooled surfaces do not give reliable results and should be avoided.
b. The point of impact should be at least 25 mm away from any edge or shape discontinuity.
c. For taking a measurement, the rebound hammer should be held at right angles to the surface of the concrete member. The test can thus be conducted horizontally on vertical surfaces (preferably) or vertically upwards or downwards on horizontal surfaces. If the situation demands, the rebound hammer can be held at intermediate angles also, but in each case, the rebound number will be different for the same concrete.
d. Around each point of observation, six readings of rebound indices are taken and average of these readings after deleting highest and minimum reading means we have to take 8 readings
e. After the average reading find out the corresponding Compressive strength from the graph .
3. TEST RESULTS
Test result should record in in prescribed format
The report shall include the following:
a) Date/period of testing
b) Identification of the concrete structure/element
c) Identification of the rebound hammer;
d) Grade of Concrete
e) Test result and hammer orientation for each test area