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Common Polishing and Grinding Mistakes

concrete polishing mistakes article

Common Polishing and Grinding Mistakes

April 2, 2019
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Most Common Polishing & Grinding Mistakes

When polishing concrete, surface preparation is where the majority of the work takes place.  To achieve quality results proper grinding is crucial. The equipment and polishing pads used can be adjusted depending on the requirements of the floor being worked on.  This article covers some of the mistakes other contractors make when polishing and grinding concrete floors.


Not Matching Diamond Hardness With Floor Hardness

The polishing pads we use are made from diamond and have different characteristics in how hard they are.  As a general rule, polishing soft concrete requires hard diamonds and polishing hard concrete requires softer diamonds.  Matching the wrong hardness results in undesired appearance because the surface gets hot meaning too much or too little friction.  In other cases the tool erodes quickly which results in poor grinding and wastes money. It is important to test the concrete hardness in a small area to see results before moving on to a larger section of the floor.

Adjusting Grinder Speed

It might be intuitive to run the grinder on max speed to polish more floor in less time.  This extra friction results in the grinding disc surfing over the floor and not grinding enough material.  By reducing the speed of the grinder it will increase the friction and the amount of material being removed. The operator needs to find that sweet spot between floor hardness, diamond hardness and grinding RPM.  This is why polishing concrete is an art. Experienced concrete polishers learn this skill with experience and can quickly adjust the grinding speed with downward pressure as needed.


Using Low Quality Diamonds

Shouldn’t diamonds cost 3 months salary?  A good quality set of diamond polishing pads cost up to $10,000.  This means there are lots of OEM products from offshore manufacturers claiming to be just as hard at a fraction of the cost.  The problem is poor quality diamonds wear down quickly, they can scratch floors and overall don’t perform well. We have tried and tested the cheaper offshore diamonds and found that the cost savings on the tool didn’t add up because of poor performance and the pads would last a fraction of the time.    


What Results Are You Trying to Achieve

What is the look you are trying to achieve on your project?  Cream finish, granular effect, aggregate exposure? Also what coating are you going to apply?  If you want to achieve a soft cream finish then you should start grinding with less aggressive diamond. Once that cream finish is grinded away it is gone forever.  When starting your grinding project start in a small test section and see what results you get. In many instances it is better to be safe than sorry. It is important to consider what finish you want to achieve before choosing how aggressive you want your grinding to be.


Grinding Too Much Too Fast

As you work on the floor you need to check the finish as you work.  If you see undesirable results on the floor you need to change the method immediately. If you are grinding with a 100G diamond and the finish is not what you desire move down to a finer grit before getting more aggressive.


Concrete polishing isn’t a recognized trade like plumbing or welding but the skills involved are similar.  These skills take time to learn. Learn how the slab is reacting to the current grit. Adjust how much pressure you apply to the machine.  An experience floor polisher is worth his weight in gold from increased productivity and completing every job with the desired results.  This is the type of experience you are getting when you hire contractors like Concrete Fusion.  Professional and amazing results every time.