In an earlier concrete polishing tip, I mentioned there are many options when choosing diamond tooling configurations and grit levels. Now we’re going to learn about another variable to consider.
Today, we’ll learn how to match a diamond tool’s metal bond to the concrete prior to choosing the grit level by correctly performing a Mohs hardness test.
The question is: How hard is the concrete you’ll be polishing and what metal-bond diamond tooling should you use for your first grind?
Doing a Mohs test prior to every first cut done dry will save time, money and improve productivity.
- The kit comes with tester pieces, which are small thin rectangular pieces of different materials that scratch on different levels. Each piece is marked which level that is.
- The objective is to use these pieces to first train your hand to use the correct amount of pressure with these guides, then test a floor.
- Hold the tool like a pencil, press the point into the tester piece and pull it forward to draw a line. When it makes a scratch, remember the amount of pressure used. Try it again until it feels natural.
- Now, hold the tool like a pencil and press the point of the #9 tester on the concrete surface and pull a line. Note mentally how much it scratched.
- When the tool leaves an etched line in the surface, it indicates that the floor is softer than the numbered tool just used.
- Continue to progress down in numbers until the numbered tool you’re using doesn’t scratch.
- Your answer will be the previous number of the one that didn’t scratch the concrete surface.
- If there is a questionable result, test another fresh/clean area of the concrete surface to establish the hardness of the floor on average. Then use the corresponding color metal-bond diamond tool to open the floor.
- The hardness test can be repeated before each step. This can be useful. Many times the cap is harder than the slab’s matrix. So, that bond color/hardness will abrade the softer bond diamond that was required to get through that hard cap resulting in excessive wear of that tooling.
Remember this simple rule: Use harder bond for softer concrete and softer bond for harder concrete
Have more questions or a suggestion for polished concrete topics? Feel free to contact Jennifer Faller at [email protected]