Before switching to a finer grit, go over the whole concrete surface meticulously with a coarse grit. To get the required polish, you must sand the whole surface numerous times, each time with a finer grit. Be cautious and take your time. Sanding a concrete surface may be necessary for a variety of reasons.
In this post, we’ll go through concrete sanding techniques and give detailed instructions for finishing a concrete sanding project.
Does Sanding Concrete Work?
It can be difficult to think that one can sand concrete given that it is a surface that is so tough and resilient that it can withstand extreme damage. Concrete may be sanded with the correct equipment and materials. Unless it’s a tiny area, you might not want to try to manually sand the concrete’s surface, but power sanders and grinders are quite good at doing the job.
Any concrete surface, whether a wall, countertop, driveway, patio, or cellar floor, is sandable.
Can Regular Sandpaper Be Used To Sand Concrete?
Concrete may be sanded using standard sandpaper. Similar to wood, concrete may be polished to a smooth surface or removed in greater quantities using discs made to fit concrete sanders. Using the proper grit of sandpaper is essential.
How to Sand Concrete the Best
Concrete may be polished with a variety of instruments, ranging from big floor polishers to hand sanding blocks. We’ll discuss each tool in more detail below so you can decide one is ideal for your project.
Sanding Concrete by Hand
Concrete may be hand-sanded to create smaller, oddly shaped items. It enables you to reach areas that mechanical sanders cannot, including tight spaces and curved surfaces. For ornamental items that cannot be securely sanded with a big angle grinder or belt sander, hand sanding is also appropriate.
Naturally, hand sanding is far more time-consuming because your arm has to perform all of the work. Large surfaces like a driveway or patio cannot be sanded because of this. Even manually sanding a concrete countertop may be time- and labor-intensive. Additionally, when sanding big areas by hand, it might be challenging.
A belt sander has a motor with two drums that rapidly rotate a loop of sandpaper. There are portable belt sanders and stationary belt sanders. The material is rubbed against the stationary belt sanders. The latter can be used to sand concrete.
For flat surfaces, a portable belt sander is a terrific tool, making countertops a perfect candidate. When used with fine-grit sandpaper, it has the capacity to remove substantial amounts of material to smooth out irregularities and polish a countertop to a bright, flawless surface. A belt sander makes it rather simple to get a uniform finish.
Handheld sanders shouldn’t be used on bigger areas like a patio or garage floor because they are still very tiny.
An angle grinder consists of a motor with a handle on the side, a circular grinding blade, and a grip on the body. Angle grinders may also be used to grind cement, despite their initial purpose of grinding down metal. They come in sizes ranging from 4-1/2 inches to 9 inches.
Grinders may remove more material at once than standard sanders because they utilize hard discs rather than softer sandpaper. They are therefore perfect for surfaces with severe irregularities. When outfitted with fine-grit discs, they can polish concrete to a flawless finish due to the tremendous amount of force they create. Additionally, they are appropriate for bigger projects since they can cover more land more rapidly.
Great power entails enormous responsibility. In this situation, if one isn’t cautious in how they use an angle grinder, it’s simpler to make gouges or uneven regions in the concrete than it is with sandpaper. This is because an angle grinder can remove more material more rapidly.
Unlike a belt sander, which can only be pushed forward and backward, this sort of portable sander moves in a random circular pattern, making it easier to move in all directions. Because of this, the orbital sander is perfect for sanding some surfaces, such a countertop or even the concrete floor of a bathroom. The orbital sander is simpler to operate than other sanders since it allows for a wider range of motion.
Just remember that not every orbital sander is made equal. Stronger orbital sanders might not have enough force to make a significant dent in concrete. Select an orbital sander with more power and amps capable of tearing through concrete.
Floor Concrete Grinder
Floor concrete grinders are big, mobile devices with a large, roughly 10-inch-diameter grinding wheel. When the motor rotates the grinding or polishing pad, you control a floor grinder by pushing it while standing. Floor grinders are perfect for sanding expansive surfaces like a whole driveway or a sizable patio due to their size. Although these devices are pricey to buy, they are reasonably priced to rent.
Best Sandpaper for Concrete
It’s essential to choose the proper grinding pad, disc, or sandpaper for the instrument you want to use to sand concrete.
Start with coarser 40–60 grit sandpaper if you need to remove a lot of material to smooth out uneven surfaces or change the appearance of the concrete. Start with sandpaper with an 80 to 120 grit rating to smooth concrete that has few imperfections. Use sandpaper with a grain between 200 and 400 if all you’re aiming for is a smooth finish. You must progressively raise the grits to 800 or higher if you want the concrete to have a glossy finish.
How to Sand Concrete Countertops or Floors
It’s time to start sanding the concrete once you’ve determined which tool you’ll employ. We’ll go through each action you need to do to finish a concrete finishing project in detail below.
Step 1: Prepare Yourself and the Space
Start the procedure by using plastic sheeting to cover any furniture that cannot be moved out of the area. You must use goggles or safety glasses that completely enclose the eyes and wear a respirator since sanding concrete will cause the air to become contaminated with hazardous particles. Wear clothing that covers all exposed skin since concrete contains silica, which can irritate skin when ground into tiny particles that can fill the air.
Step 2: Examine and Correct
Look for any cracks or chips in the concrete surface, and then fill up those places using concrete filler. Before beginning to sand, let the filler dry fully.
After it has dried, wash the area with a solution of water and laundry detergent. To remove any stains from the concrete, use an industrial-strength cleaner like hydrogen peroxide, TSP, or ammonia. When handling these chemicals, ensure sure the location is sufficiently ventilated and that you are wearing gloves and eye protection.
Step 3: Select Your Sandpaper
To start the sanding operation, decide between sandpaper and turbo cups. Both are available in a wide variety of grit sizes, from coarse to fine.
You may utilize turbo cups, which have a metal disk and a diamond-studded edge, with a hand-held grinder. The grinder can remove more material with each pass thanks to turbo cups, which have a diameter of between 5 and 6 inches and can cut through concrete more quickly than sandpaper.
Turbo cups have varying grit levels, just like sandpaper. The disc is coarser the lower the number.
Use a handheld grinder and turbo cup if you need to remove a thicker layer of material to get the finish you want. Use an orbital sander and sandpaper if you only intend to conduct light sanding and polishing.
Diamond pads are an additional choice. Diamond pads are made of thin plastic that has diamonds embedded throughout. They are less effective because they are less forceful than cups. They are available in grit sizes ranging from coarse 50 grit to fine 3,000 grit, which are perfect for polishing surfaces.
It’s crucial to sand in a specific order, whether you’re using sandpaper, diamond pads, or cups. Start with a coarse grit of around 50 and progressively move to finer grit levels by going to 200, 500, and finally 3,000 for polishing. Avoid trying to skip forward since the scratches made by 50-grit sandpaper won’t be able to be removed by very fine sandpaper.
Think about the finish you want when selecting your sandpaper. The top layer of the surface must be polished to a smooth finish in order to smooth the concrete. The surface will become more reflective the finer the grit you use to polish it.
A more severe sanding process entails removing a tiny portion of the top layer of the surface to reveal the sand beneath. As a result, the concrete has a salt-and-pepper appearance.
An exposed aggregate finish will be produced by more thorough sanding that entails removing a sizable amount of debris, allowing the concrete’s aggregate to be seen. Depending on the size of the work, you’ll need to use either a floor grinder or an angle grinder to get this sort of finish.
Step 4: Begin sanding
Choose between a wet and a dry approach before you start. Water is used as a lubricant during the sanding process in wet sanding. By lowering friction, the pads are kept cool and last longer. Dust can also be reduced by being dampened; this reduces the quantity of dust that becomes airborne.
In addition to being dirty, wet sanding wastes a lot of water by producing a slurry that must be cleaned up and disposed of as you go. It’s extremely challenging to get a glossy finish using this technique.
You can get better results by dry sanding, especially if your concrete surface has a glossy finish. No water is wasted, and no pasty residue is left behind for you to clean up. While dust is undoubtedly a problem, many concrete grinders and polishers now feature dust extraction systems that collect dust as it is generated, reducing the amount that is released into the atmosphere.
Start sanding with coarse grit to get rid of any stains or irregularities. After the concrete is stain-free, use an 80 grit sandpaper or grinding disc that is finer. As you move from one corner to the next, be sure to cover the full space.
Move on to a finer 150 grit level when you’ve done sanding the concrete with the 80 grit disk or sandpaper, then move on to 200 and 400 grit levels. Although 400 grit is frequently sufficient to polish concrete to a shining finish, you might want to move up to a higher grit level if you’re not happy with the result. Make sure you’ve eliminated all the scratches left by the preceding pad before switching to a finer grit.
Step 5: Apply a hardener
After sanding is finished, use a chemical hardener. Concrete will be solidified by a hardener to provide a tough finish that will withstand wear and tear better. Apply the concrete after using an 80 grit disk if it is moderately hard. Apply the hardener after using a 200-grit disk for harder concrete.
To properly spread the hardener throughout the surface, you will need a sprayer.
6th step: polish
Wait for the hardener to dry before using a 3,000 grit disk or sandpaper to polish the concrete surface. Make sure to cover the whole area. The concrete will be polished to a very glossy appearance using this high grit sandpaper or grinding disk.
Polishing is finished using a buffer once any dust has been removed from the surface.
Step 7. Sealant application
Apply a concrete sealer after giving the countertop plenty of time to cure, especially if you used the wet approach to sand or grind it. With the help of this sealer, the surface you’ve worked so hard to repair will be shielded against stains caused by water, oil, and other liquids.
Sanding Concrete Walls
As with the aforementioned technique, start by washing the walls with dish soap and water. Make use of an industrial-strength cleaner to get rid of tough stains. Sand the wall using a portable grinder equipped with a diamond sanding pad after allowing it to dry.
From one end of the wall to the other, push evenly on the wall going back and forth and up and down, being careful not to miss a place. In the same manner as previously, start with coarse grits and then go to finer grits to polish the wall to a smooth finish. When finished, add a hardener and a sealer to shield the wall from more stains.
Steps for Sanding a Concrete Patio
Start by removing all patio furniture and grills, then protect any neighboring vegetation from the concrete dust by covering it with drop cloths. Clean up any dirt on the patio floor with a brush. Use a dish detergent or chemical cleansing solution to get rid of any stains if necessary.
Put the sanding disks on a floor grinder with an orbital drive. Pass the grinder over the floor, moving it from side to side to smooth down the surface and eliminate irregularities, fissures, and other flaws.
As you progress from 300 to 800 grit disks, add finer ones until you have the finish you want. Use a 1,500-grit disk for a glossy shine. Clean up by removing any concrete dust with a shop vacuum.
Clean the patio completely with a power washer, then give it two days to dry. Using a long-handled roller brush, treat the patio with penetrating sealer twice.
How to Hand Polish Concrete
Even if machine polishing of concrete can be the preferable technique, hand polishing of concrete is also an option. In some circumstances, manually polishing concrete is the best option.
You’ll need the appropriate tools for this. When hand polishing concrete, conventional sandpaper isn’t tough enough to leave much of a dent. The best solution is diamond polishing pads, like those from Toolocity.
These pads with diamond studded surfaces are strong enough to cut through the concrete. When using power techniques, you should begin with coarse grit and work your way up to finer grits. Avoid skipping steps because course sanding blocks leave marks that can’t be removed by finer grit sanding blocks.
Should Concrete Be Sealed After Sanding?
Although it’s not required, sealing the concrete after sanding only makes sense if you’re going to the trouble of sanding and polishing it. Concrete is porous, which makes it a fluid-absorbent material. This means that concrete may be readily stained by oils and chemicals. Additionally, it becomes more prone to cracking and chipping.
Concrete may be protected by sealing it to make the surface water resistant. In addition to safeguarding the concrete’s surface, sealing also gives it a completed appearance by intensifying its color and giving a glossy sheen.
What is the best way to sand down concrete?
Use sandpaper with a grain between 40 and 60 for basic sanding. Use 80-120 grit sandpaper to smooth up little imperfections. Use superfine sandpaper with a grit of 200–400 for a flawless finish and smoothness. If there are significant flaws, a floor grinder or specialized diamond disc is required.
What is the best tool for sanding concrete?
A hand grinder or orbital grinder is the best choice for finely sanding concrete countertops or other tiny, precise surfaces. A walk-behind grinder will cover the largest surface area if you wish to polish bigger surfaces, such as whole concrete floors, slabs, or patios.
Can rough concrete be smoothed?
If the concrete is exceedingly rough or has bigger flaws that sandpaper cannot remove, a concrete grinder could be required. If there isn’t enough vertical room for additional layer of concrete, a grinder might be useful. By doing this, the floor may be smoothed without the need for additional surface thickness.
What kind of sander is used for concrete?
When sanding concrete, the orbital sander is the best instrument to use. This will substantially lessen your work and give the counter or fixture a consistent shine. The fact that they are portable and have small faces is the only drawback. Look for something larger if you are sanding a whole concrete floor.
Can I sand concrete with a belt sander?
To sand concrete to a shining surface, use a disc, belt, or concrete grinder together with ordinary sandpaper discs or diamond-encrusted pads. There are several justifications for taking on such a difficult endeavor.
How do you make concrete smooth?
In order to level out a sloping concrete floor, self-leveling cement can be used. Applying and pouring Ardex or other comparable self-leveling cementitous mixtures on the surface and then grinding it afterwards to get a smooth sheen are also options.
Can I sand concrete with sandpaper?
You might be wondering if you can sand concrete with normal sandpaper given the make-up of concrete and how difficult it is. Concrete may be sanded, although ceramic and aluminum oxide sandpaper aren’t the best options for the job. Use diamond sanding or polishing pads as much as possible.
How do you sand and polish concrete?
Using a wet diamond polishing disc (100 grit or 200 grit) linked to a standard random orbit sander is the easiest and fastest way to accomplish this. Spray some water over the concrete to moisten it, then use the diamond disc to “sand” the surface to remove the burnished finish.
Why does my concrete look rocky?
Your concrete seems rough mostly because it wasn’t properly tamped and floated. What you are truly seeing when you look at a smooth concrete patio, driveway, sidewalk, or set of steps is cement and sand. This is the result of masonry workers smoothing the surface after tamping the stones down.
What is the cheapest way to level a concrete floor?
Self-leveling coatings are available for filling voids and fissures. If you want to make the change more gradual, you may also consider utilizing vinyl floor tiles. The most straightforward (and affordable) solution would be to purchase a large diamond grinding wheel and bevel the lip.
Should I use water when grinding concrete?
The main justification is that utilizing water while operating a concrete grinder on a slab enhances performance and results, and this alone can be sufficient. By adding lubrication between the tooling and slab while using water, heat and friction are reduced.
What is the fastest way to grind concrete?
An aggressive wheel removes material more quickly but creates a rougher surface since it may remove up to 1/4 in. of concrete. A less aggressive wheel leaves a smoother surface and removes less concrete.
Should you grind concrete wet or dry?
Wet concrete grinding is more worse for the environment than dry concrete grinding, unless it is absolutely essential. Slurry, a combination of concrete particles and cooling water, is the byproduct of wet grinding.
Can I use an orbital sander to polish concrete?
There are better choices available, and using an orbital sander to polish concrete is not ideal. But it’s not insurmountable; with a little work and the right equipment, you can create a polished concrete surface that is smooth.
How do you fix rough broomed concrete?
There are two ways to improve the imperfect finish. One is to grind or polish the surface, which would smooth the concrete’s surface and eliminate the rough broom finish. Your walkway and patio would have a wonderful smooth ornamental look since some of the aggregate would be exposed.