Flagstone is a flat stone that is used to pave slabs, driveways, patios, flooring, etc.
Flagstone is often installed with sand and portland cement. After installation, the flagstone is often left with cement residue which can be difficult to clean if you don’t know how to. If you don’t want to employ professional help which is quite expensive, then this article is for you.
I’ll be showing you very simple and effective ways of cleaning cement off flagstones. Whether the cement has been on your flagstone for a while or recently, these methods are equally applicable and they are more simple than you thought. Let’s get right into them.
How to Clean Cement off Flagstone (9 Methods)
Method 1: Cleaning Cement off Flagstone With Brush & Warm Water
This method works better on a newly installed flagstone while the cement residue is still wet. You may try it on dry cement but it may not be as efficient.
1- Stiff nylon brush
2- Warm water
STEP 1: Pour some warm water into a bucket. The quantity depends on the size of the flagstones you’ll be cleaning.
STEP 2: Use a bowl to pour the warm water on your flagstone and scrub the cement residue as you pour.
STEP 3: Do this over and over again until the residue disappears.
STEP 4: Rinse the flagstone thoroughly.
Method 2: Cleaning Cement off Flagstone With Coca-Cola
Using soda like coca-cola to clean may come as a surprise to you but it works like magic. More than you would believe. Coca-Cola contains carbonic acid which not only gets rid of dirt but also takes care of mold and mildew that may be present in your bathroom, toilet, kitchen, etc.
It works well in getting rid of cement residue on flagstone and it works fast. If it’s a newly installed flagstone, allow the cement to dry before applying this method.
STEP 1: Get a bottle or can of coca-cola. You can get more if the area you’ll be cleaning is large. Pour the coca-cola on the cement residue or the area you would like to clean.
STEP 2: Use the brush to scrub the residue as you pour the coca-cola. Do this until the residue is gone and the spot is clean, then move on to the next spot.
STEP 3: After the cleaning is done, rinse the flagstone with water thoroughly.
Method 3: Cleaning Cement off Flagstone With Muriatic Acid
Muriatic acid works best in cleaning cement when the cement is already dry. This means you can’t use it to clean cement off a newly installed flagstone. Warm water and some detergent will do that.
Muriatic acid when applied to dried cement, eats at it and dissolves it, cleaning it away effectively from your flagstone. Muriatic acid can also be used to get rid of mold and algae.
You must take all necessary precautions when using muriatic acid. Muriatic acid is a harmful chemical that can do serious damage to your health. It can cause chemical burns when it comes in contact with your skin, choking and shortness of breath, and also eye damage.
1- Muriatic acid
2- Garden hose
3- Safety goggles
4- Long rubber gloves
6- All plastic bucket
7- Stiff bristled brush
STEP 1: Use a garden hose to saturate your flagstone with water. The cement needs to be wet before you can apply Muriatic acid.
STEP 2: Pour 1 gallon of water into an all-plastic bucket and add 1 cup of muriatic acid. If you want a stronger solution you can mix 10 parts of water with 1 part of Muriatic acid.
STEP 3: Use a stiff-bristled plastic brush to apply the solution to your flagstone, paying attention to the areas with cement residue. The cement will begin to bubble and dissolve.
STEP 4: When the cement stops bubbling, use a brush to scrub your flagstone immediately. The acid shouldn’t sit on your flagstone for too long.
STEP 5: Rinse with water thoroughly. Then scrub the flagstone with a different brush.
STEP 6: Mix a gallon of water with 1 cup of ammonia and pour the solution on your flagstone. This will neutralize the acid residue on your flagstone and the plants that may be around it.
STEP 7: Rinse with clean water thoroughly.
You can check this recommended Muriatic Acid here.
Method 4: Cleaning Cement off Flagstone With Acid Replacement
Acid replacements are not only effective in cleaning, but they are also very safe. Unlike acids that can be harmful when they touch the skin or enter the eye, acid replacements do not harm the user.
You should however still be careful and take necessary precautions to protect your skin. Wear rubber gloves.
They clean cement residue off flagstone easily and effectively without leaving stains.
There are several types of acid replacements from different manufacturers, that can be easily bought in stores.
2- Rubber gloves
4- Acid replacement
6- Spray bottle
STEP 1: Use a scraper to chip away as much cement residue as you can from your flagstone.
STEP 2: After scraping the cement off, use a hose to saturate your flagstone with water.
STEP 3: Wear your rubber gloves and mix the acid replacement with water. You should check your acid replacement label for the instructions on the acid to water ratio. It all depends on the manufacturer of the acid replacement you chose.
STEP 4: Spray the solution generously on the cement residue on your flagstone.
STEP 5: Wait for the solution to dissolve the cement. The cement will bubble as it dissolves. That’s how you know it’s working.
STEP 6: When the cement stops bubbling, scrub it with a hard bristle brush.
STEP 7: Repeat the above steps until all cement residue is gone.
STEP 8: Rinse thoroughly with clean water.
Method 5: Cleaning Cement off Flagstone With Sandpaper
Sandpaper is coarse and has different grit levels. Applying it to the cement residue on your flagstone will create friction that will sand the cement away.
STEP 1: Use a scraper to chip away the layers of dried cement on your flagstone.
STEP 2: After scraping most of the dried cement, use coarse sandpaper to sand away the residue until there is nothing left.
STEP 3: Rinse your flagstone and wipe with a damp rag. Then rinse again thoroughly.
Method 6: Cleaning Cement off Flagstone With Vinegar
Vinegar contains acetic acid which is a weak acid that is less corrosive. It poses no risk to your health as it is skin-friendly and doesn’t produce toxic fumes.
Vinegar is also a household cleaning agent that works effectively in getting rid of stains, mold, mildew, and rust. It is used to clean cement off flagstone without damaging the surface of the stone.
1- White vinegar
STEP 1: Mix equal parts of white vinegar and water in a bowl.
STEP 2: Pour the solution into a spray bottle and spray the cement you want to get rid of, on your flagstone.
STEP 3: Allow the solution to sit for like 5 minutes after spraying.
STEP 4: Scrub the cement off your flagstone with a brush until it is completely gone. Spray more solution on a stubborn spot and scrub again.
STEP 5: Rinse the flagstone with water.
This is the recommended Vinegar for cleaning.
Method 7: Cleaning Cement off Flagstone With Sulfamic Acid
Sulfamic acid is less corrosive when compared to Muriatic acid. It cleans cement off flagstone without damaging the stone surface or causing discoloration.
1- Sulfamic acid
4- Garden hose
6- Scrub brush
STEP 1: Pour a gallon of water in a bucket and add 3/4 cup of Sulfamic acid. Wear rubber gloves to protect your skin before doing this.
STEP 2: After mixing, use a scrub brush to apply the solution to the areas with the cement.
STEP 3: Allow the solution to sit for about 2 minutes.
STEP 4: Scrub with a brush and then rinse thoroughly.
STEP 5: Allow the flagstone to dry. If you notice areas that are yet to be free of cement, repeat the process on those areas.
Method 8: Cleaning Cement off Flagstone With Hg Natural Stone Cement and Lime Film Remover
This product can be bought in stores or online. It is easy to use, effective and does not damage flagstone.
1- HG natural stone cement and like film remover
3- Scrub brush
STEP 1: Wear your gloves and pour 5 liters of water into a bucket. Add 1/2 liter of HG cement remover and mix.
STEP 2: Wet the surface of your flagstone thoroughly in preparation for the cleaning.
STEP 3: Apply this solution to your flagstone with a mop. Treat not more than 10-15 m2 at a time. It makes it easier to manage the cleaning.
STEP 4: Scrub the area with a brush after applying the solution and leave it for 5 minutes.
STEP 5: After 5 minutes, remove the solution from the area with a mop. Then mop again with clean water until the solution is completely cleaned. Your flagstone would have been cement-free.
Method 9: Cleaning Cement off Flagstone With Grout Haze Remover
There are two methods of using a grout haze remover and they require different grout haze remover products. These products are easy to buy and they are also safe to use.
Option A: Cleaning Cement With Grout Haze Clean-Up
This first product and this method are used within 10 days of installing the flagstone. Anything more than 10 days, you have to use the second method to remove the cement.
2- Grout Haze clean-up
4- Brush/Scrub pad
STEP 1: Sweep the flagstone to get rid of dust and dirt.
STEP 2: Mix Grout Haze clean-up with water. 1 part of clean-up with 5 parts of water is adequate.
STEP 3: Apply the solution to the flagstone. Treat no more than 10 sq. ft at a time. This is more manageable.
STEP 4: Leave the solution on that particular area for about 10 minutes or more.
STEP 5: After 10 minutes, scrub with a brush or scrub pad, then mop it up.
STEP 6: Rinse with water thoroughly and use a different mop to remove the water.
Option B: Cleaning With Cement Grout Haze Remover/ Phosphoric Acid Substitute
You can use either of these two products above. They both work effectively and produce near the same results. This method is used if your flagstone has been installed for more than 10 days.
1- Rubber gloves
2- Cement grout cleaner/Phosphoric acid
6- Brush/Scrub pad
STEP 1: Wear your rubber gloves and mix Cement grout cleaner/ phosphoric acid with water. Add 1 part of the product chosen to 5 parts of water.
STEP 2: Sweep the flagstone in preparation for cleaning to remove dirt and dust.
STEP 3: Wet the flagstone with water after cleaning.
STEP 4: Use a mop to apply the solution to the flagstone. Work with a manageable area of 10sq. ft. Apply the solution generously as it must not dry on the flagstone.
STEP 5: Allow the solution to sit for about 2 minutes.
STEP 6: Scrub the cement on the flagstone well and mop up the solution after scrubbing.
STEP 7: Rinse the area and scrub again as you rinse.
STEP 8: After cleaning the whole area, rinse with a garden hose thoroughly with lots of water.
There you have it! The most common types of problems with cement or concrete benches are grease, surface dirt, paint marks, mold, and rust.
The methods shown in this article tackle all these problems quite well and have been tested many times.