The Schmidt rebound hammer is principally a surface
hardness tester. The Original Schmidt is available in models with different
impact energies, each test hammer designed for a specific test application.
The Romans were aware of the fact that good mortar (opus caementicium) is hard and of a high compressive strength. They tested its quality subjectively by scratching the surface with an iron nail.
The Romans were aware of the fact that good mortar (opus caementicium) is hard and of a high compressive strength. They tested its quality subjectively by scratching the surface with an iron nail.
originally found here:- http://www.reboundhammer.com/schmidt-rebound-hammer.html