Rebound Hammer - Two Measuring Principles

Rebound hammers are used to determine the compressive strength of concrete. Compressive strength test results are, among other things, used to determine that the concrete mixture as delivered meets the requirements of the specification. Structural failures due to weaker than defined concrete mixes can be catastrophic and may lead to loss of life. Therefore, quality checks are of paramount importance to serious construction companies. In addition, non-destructive testing is faster and far more economical than destructive testing on samples.

Mechanical rebound hammer measure the mechanical travel of the hammer mass on the rebound. It is affected by its friction on the guide rod, the friction of the drag pointer on the scale, the influence of gravity during its travel and the relative velocity between unit and mechanical parts.
Electronic rebound hammers, on the other hand, use the true rebound coefficient that represents the physical rebound coefficient: Q = 100*((Energy Restored)/(Energy Input))
These rebound hammers measure the velocity of impact and of rebound, immediately before and after the impact, computing the fraction of energy loss to the specimen under test. The true rebound coefficient is virtually free of error sources inherent in traditional concrete test hammers. It is measured optically making the use of a drag and drop pointer redundant. Thus the true rebound coefficient is less dependent on friction on the guide rod, the influence of gravity during the travel of the drag pointer and the relative velocity between unit and specimen. Rebound hammers that measure with the true rebound coefficient do not need correction for the impact direction. Consequently, impact direction conversion curves as required with mechanical hammers, are also redundant.


To find out more about roll hardness testing visit us at Proceq

Proceq manufactures quality nondestructive portable testing instruments for metal hardness, concrete properties and roll hardness tester. Proceq invented the Equotip portable metal hardness tester and the world’s first portable concrete test hammer, the Schmidt concrete test hammer.