The rebound reading on
the indicator scale has been calibrated by the manufacturer of the rebound
hammer for horizontal impact, that is, on a vertical surface, to indicate the compression strength. When used in any other position, appropriate correction
as given by the manufacturer is to be taken into account.
Hammer test can provide fairly accurate estimate of concrete compression strength, it performed with precautions and co- relations:
Hammer test can provide fairly accurate estimate of concrete compression strength, it performed with precautions and co- relations:
1.
Concrete
Age: The concrete should be
14 to 56 days old.
2.
Surface
Condition: The surface of the
concrete at the point tested must be smooth dry and free of honey combing.
Otherwise, rebound readings will be low indicating a weaker concrete than is
actually the case .
3.
Location
of Test Point: The concrete to be
tested must be at least 100 mm thick. Care must be taken that the test points
are no closer than 25 mm from the edge.
No. of Readings: Calculate the average of 10
readings and exclude extreme readings (if any) and recalculate average using
the remaining readingsoriginally found here:- http://www.reboundhammer.com/testing.html