MOH's hardness test.
The MOH's hardness test is a good way of testing the surface hardness of different materials. We use the test to determin the hardness of concrete before we start machining it as this has a profound effect on the type of diamonds we are going to use. If concrete is soft it is very abrasive on the diamond tooling and if it is very hard the tooling can glaze over and stop cutting. The test gives us a fairly accurate guide to which bond of diamond we should start with but the test should be carried out again once the top layer of concrete is removed because the hardness of concrete can change a few millimeters under the surface.
The test is straight forward, you scratch the surface ( only the same pressure as if you were writing on paper ) of the concrete starting with 8 or 9 ( the test points are numbered 2-9 ) then work your way down through the sequence until no scratch is visible. So if 5 leaves a scratch and 4 doesn't then the floor is a 4.5.