How to Polish Concrete
Evaluate the concrete., Clean the surface., Repair any cracks., Acquire a concrete grinder., Wear protective gear., Grind the concrete with the coarsest disc., Progress through several grit sizes., Apply densifier in the middle of the process., Pass...
Step-by-Step Guide
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Step 1: Evaluate the concrete.
Use a Mohs hardness pick to determine the degree of mineral hardness.
Determining whether the concrete is soft, medium, or hard will allow you to fine-tune the polishing process.
Use the tools supplied in the kit to test the hardness of the concrete against the hardness of other minerals.
The softest mineral that is capable of scraping the concrete is harder than the concrete, placing the concrete's level of hardness directly below that mineral. -
Step 2: Clean the surface.
Prepare a solution of warm water and household detergent, then scrub the concrete thoroughly using that solution and a bristle brush.
Rinse away any suds and let the area dry.For especially stubborn stains or mold, you might need to use a stronger cleanser.
Hydrogen peroxide, ammonia, and TSP are common options, but do not mix these chemicals together.
Choose and use only one chemical.
Wear protective gloves and eye goggles before handling any chemicals.
Keep the area well-ventilated, too. , If there are any cracks in your concrete surface, you should repair them before you polish it.Purchase specialized concrete crack filler.
Follow the instructions on the package to mix the filler, then squeeze it directly into the crack.
Allow the filler to set completely before moving onto the next step. , You'll need to use a specialized tool to grind concrete; a standard sander will not be enough.
You can usually rent concrete grinders from most hardware stores.
Before agreeing to rent the grinder, make sure that it feels comfortable enough for you to use.
Note that renting a grinder can cost as much as $1000 per week, so this project may not be especially cost-effective if you're only working with a small concrete surface. , Before handling the grinder, you should prepare yourself by wearing a dust mask, gloves, safety goggles, and ear plugs.While not strictly necessary, you may also want to wear a helmet to protect your head in the event of an accident.
This is especially important if you are working in an area currently undergoing other construction.
Wear work shoes with a good grip, too.
Even if you feel fairly confident about your home improvement skills, accidents happen, and no-slip shoes can help prevent accidents caused by sliding, slipping, or falling over. , If you need to remove sealer, stain, or other contaminants that wouldn't wash off, start with a 40-grit grinding disc.
If you do not need to remove anything, though, skip directly to an 80-grit disc.
Note that these discs must be metal-bonded diamond discs.
Non-diamond discs will not be hard enough to grind down the concrete.
Keep in mind that lower grit values indicate coarser discs.
In other words, 40-grit discs are coarser than 80-grit discs.
Follow the instructions that come with your grinder to determine the proper way to attach discs and power the machine.
Pass over the entire concrete surface, gradually working from one corner to the diagonally opposite corner. , You will need to use at least two or three more grinding discs.
Choose discs that are progressively higher (less coarse) in grit-size.The exact grit sizes may vary depending on the hardness of your concrete.
As a general guideline, however, follow the 40-grit disc with an 80-grit disc.
Move onto 150-grit after that, followed by 200-grit, and possibly 400-grit.
Pass over the entire surface with each new disc.
For each new disc level, the idea is to buff away any scratches made from the previous grinding disc.
Accomplish this task by crossing over scratch lines in a perpendicular direction. , Spray liquid chemical hardener over the surface to help solidify the concrete.The best time to densify the concrete will vary depending on the original degree of hardness.
Return to the results of the Mohs hardness test.
For soft to medium concrete, apply the densifier after using the 80-grit disc.
For medium to hard concrete, apply the densifier after using the 200-grit disc.
Follow the manufacturer's instructions when determining how to apply the densifier.
Typically, you'll need to pour the product into a small sprayer.
Use the nozzle of the sprayer to coat the entire concrete surface, then let it dry before continuing. , After your primary grinding and densifying, attach a 3000-grit disc to the grinder.
Work over the entire concrete surface with this disc, moving from one corner to the diagonally opposite one.
This grit on this disc is so fine that it will actually begin polishing the surface.
You can skip this step if absolutely necessary, but following it will give the finished concrete a high-gloss appearance. , Grinding the concrete produces plenty of dust and debris.
After you finish all of the grinding, you should vacuum as much debris as possible using a shop vac.
Note that some concrete grinders come with their own vacuum.
In these instances, use that vacuum instead of a separate shop vac.
You can also vacuum the surface in between disc switches, but doing so is not typically necessary.
One thorough vacuuming before you buff the concrete should suffice. , Remove the grinding disc from your concrete grinder and attach a burnishing pad.
Pass over the entire concrete surface using this pad.Working the concrete with the burnishing pad should buff the concrete and make it notably smooth.
If you do not have a burnishing pad for your concrete grinder, or if the machine does not have an appropriate setting for use with a burnishing pad, use a low-speed brush-style buffer instead. , Choose a water-based or solvent-based concrete sealer and follow the manufacturer's instructions when applying.
Some sealers need to be rolled, while others should be sprayed onto the surface.Sealers protect the concrete against grease, dirt, and other stains.
Moreover, using a glossy sealer should give the polished concrete more of a sheen.
No matter which type you use, the standard coverage rate is 250 to 300 square feet (23.2 to
27.9 square meters) of concrete per 1 gallon (4 L) of sealer.
Apply two thin coats instead of one heavy coat.
Wait for two to four hours for the first coat to dry before applying a second, then apply the second coat in a direction lying perpendicular to the first coat.
After applying the second coat, wait another two or four hours before moving onto the next step. , Pass over the sealed surface once more with the burnishing pad or buffer.
Work slowly and thoroughly, covering the entire surface at an even pace.
Move in the direction lying opposite/perpendicular to the direction in which your applied your last layer of sealer.
When you finish this final pass, the concrete should look as smooth and glossy as finished stone. , Allow the final coat of sealer to completely dry before you actively use the concrete surface.
The exact amount of time will vary depending on the manufacturer, but it will usually be between 24 and 72 hours.
After you wait the appropriate amount of time, the polished concrete should be finished and ready for active use. -
Step 3: Repair any cracks.
-
Step 4: Acquire a concrete grinder.
-
Step 5: Wear protective gear.
-
Step 6: Grind the concrete with the coarsest disc.
-
Step 7: Progress through several grit sizes.
-
Step 8: Apply densifier in the middle of the process.
-
Step 9: Pass over the concrete with 3000-grit.
-
Step 10: Vacuum any debris.
-
Step 11: Switch to a burnishing pad.
-
Step 12: Apply one or two thin coats of concrete sealer.
-
Step 13: Burnish the surface once more.
-
Step 14: Wait at least 24 hours before use.
Detailed Guide
Use a Mohs hardness pick to determine the degree of mineral hardness.
Determining whether the concrete is soft, medium, or hard will allow you to fine-tune the polishing process.
Use the tools supplied in the kit to test the hardness of the concrete against the hardness of other minerals.
The softest mineral that is capable of scraping the concrete is harder than the concrete, placing the concrete's level of hardness directly below that mineral.
Prepare a solution of warm water and household detergent, then scrub the concrete thoroughly using that solution and a bristle brush.
Rinse away any suds and let the area dry.For especially stubborn stains or mold, you might need to use a stronger cleanser.
Hydrogen peroxide, ammonia, and TSP are common options, but do not mix these chemicals together.
Choose and use only one chemical.
Wear protective gloves and eye goggles before handling any chemicals.
Keep the area well-ventilated, too. , If there are any cracks in your concrete surface, you should repair them before you polish it.Purchase specialized concrete crack filler.
Follow the instructions on the package to mix the filler, then squeeze it directly into the crack.
Allow the filler to set completely before moving onto the next step. , You'll need to use a specialized tool to grind concrete; a standard sander will not be enough.
You can usually rent concrete grinders from most hardware stores.
Before agreeing to rent the grinder, make sure that it feels comfortable enough for you to use.
Note that renting a grinder can cost as much as $1000 per week, so this project may not be especially cost-effective if you're only working with a small concrete surface. , Before handling the grinder, you should prepare yourself by wearing a dust mask, gloves, safety goggles, and ear plugs.While not strictly necessary, you may also want to wear a helmet to protect your head in the event of an accident.
This is especially important if you are working in an area currently undergoing other construction.
Wear work shoes with a good grip, too.
Even if you feel fairly confident about your home improvement skills, accidents happen, and no-slip shoes can help prevent accidents caused by sliding, slipping, or falling over. , If you need to remove sealer, stain, or other contaminants that wouldn't wash off, start with a 40-grit grinding disc.
If you do not need to remove anything, though, skip directly to an 80-grit disc.
Note that these discs must be metal-bonded diamond discs.
Non-diamond discs will not be hard enough to grind down the concrete.
Keep in mind that lower grit values indicate coarser discs.
In other words, 40-grit discs are coarser than 80-grit discs.
Follow the instructions that come with your grinder to determine the proper way to attach discs and power the machine.
Pass over the entire concrete surface, gradually working from one corner to the diagonally opposite corner. , You will need to use at least two or three more grinding discs.
Choose discs that are progressively higher (less coarse) in grit-size.The exact grit sizes may vary depending on the hardness of your concrete.
As a general guideline, however, follow the 40-grit disc with an 80-grit disc.
Move onto 150-grit after that, followed by 200-grit, and possibly 400-grit.
Pass over the entire surface with each new disc.
For each new disc level, the idea is to buff away any scratches made from the previous grinding disc.
Accomplish this task by crossing over scratch lines in a perpendicular direction. , Spray liquid chemical hardener over the surface to help solidify the concrete.The best time to densify the concrete will vary depending on the original degree of hardness.
Return to the results of the Mohs hardness test.
For soft to medium concrete, apply the densifier after using the 80-grit disc.
For medium to hard concrete, apply the densifier after using the 200-grit disc.
Follow the manufacturer's instructions when determining how to apply the densifier.
Typically, you'll need to pour the product into a small sprayer.
Use the nozzle of the sprayer to coat the entire concrete surface, then let it dry before continuing. , After your primary grinding and densifying, attach a 3000-grit disc to the grinder.
Work over the entire concrete surface with this disc, moving from one corner to the diagonally opposite one.
This grit on this disc is so fine that it will actually begin polishing the surface.
You can skip this step if absolutely necessary, but following it will give the finished concrete a high-gloss appearance. , Grinding the concrete produces plenty of dust and debris.
After you finish all of the grinding, you should vacuum as much debris as possible using a shop vac.
Note that some concrete grinders come with their own vacuum.
In these instances, use that vacuum instead of a separate shop vac.
You can also vacuum the surface in between disc switches, but doing so is not typically necessary.
One thorough vacuuming before you buff the concrete should suffice. , Remove the grinding disc from your concrete grinder and attach a burnishing pad.
Pass over the entire concrete surface using this pad.Working the concrete with the burnishing pad should buff the concrete and make it notably smooth.
If you do not have a burnishing pad for your concrete grinder, or if the machine does not have an appropriate setting for use with a burnishing pad, use a low-speed brush-style buffer instead. , Choose a water-based or solvent-based concrete sealer and follow the manufacturer's instructions when applying.
Some sealers need to be rolled, while others should be sprayed onto the surface.Sealers protect the concrete against grease, dirt, and other stains.
Moreover, using a glossy sealer should give the polished concrete more of a sheen.
No matter which type you use, the standard coverage rate is 250 to 300 square feet (23.2 to
27.9 square meters) of concrete per 1 gallon (4 L) of sealer.
Apply two thin coats instead of one heavy coat.
Wait for two to four hours for the first coat to dry before applying a second, then apply the second coat in a direction lying perpendicular to the first coat.
After applying the second coat, wait another two or four hours before moving onto the next step. , Pass over the sealed surface once more with the burnishing pad or buffer.
Work slowly and thoroughly, covering the entire surface at an even pace.
Move in the direction lying opposite/perpendicular to the direction in which your applied your last layer of sealer.
When you finish this final pass, the concrete should look as smooth and glossy as finished stone. , Allow the final coat of sealer to completely dry before you actively use the concrete surface.
The exact amount of time will vary depending on the manufacturer, but it will usually be between 24 and 72 hours.
After you wait the appropriate amount of time, the polished concrete should be finished and ready for active use.
About the Author
Jennifer Mendoza
Committed to making practical skills accessible and understandable for everyone.
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