How to Test Concrete Hardness using a MOHS Scale

Concrete is made up of various elements of different hardness and densities that vary from region to region. Use of these picks is limited to providing a general guide for surface harness.

Steps to testing:

1. Start with a pick with a higher number than the surface being tested is believed to be. For beginners, start with pick #9 until more experienced and you have a general feel for the concrete in your area.
2. Grasp the pick in the same fashion as you would a pen and place the edge of your palm on the floor as if ready to write.
3. Reach forward with the pick and draw a 2” line towards you using the same downward pressure you would use if writing with a pen on paper.
4. You will notice the #9 pick will easily produce a scratch. Subsequent picks, will leave less and less of a scratch. Do NOT force any of the picks to scratch.
5. Continue down through the scale until you encounter the pick that will not scratch the surface. For example if #5 leaves a scratch but #4 does not, then the floor is about 4.5 on the MOHS scale.
6. Sometimes the metal from the pick will lay down and look like a scratch. A magnifying glass will help you to see the scratch or line left by the pick.
7. If you are unsure whether the pick left a scratch, lightly drag the pick perpendicular across the first line. If there is a scratch, you will feel the pick drop into the grove.
8. Always test in different locations of the floor in order to get a more accurate result. There may be more than one pour present in different areas of the floor, which may give widely varying results
9. Be alert for signs of micro-topping, self leveling or filling/patching compounds. Look at different colors, textures or possible edge delamination for clues.
10. To increase your knowledge of the aggregates used in your area, do a scratch test on individual stones that are exposed during the grinding, polishing process.
11. The picks should always be sharp and in good condition. There is a small stone in the kit that can be used for dressing the tip.
12. The picks have extremely sharp points. Care should be used when handling them.
13. Never place a loose pick in any pocket or article of clothing.
14. It must be remembered that the picks and instructions are only a guide and do NOT cover every possible situation.

North American Aggregate Classification Map