Do you sweep or clean the concrete of your garage floor only to have it feeling gritty and dusty the next day? Even after washing it down, can you can run your fingers over the concrete once it is dry and get a white, dusty film on your fingertips? If so, you may have a problem with concrete dusting. The good news is that dusting of your garage floor can be stopped or significantly reduced in most cases.
What is concrete dusting and what causes it?
Dusting is the white chalking and/or powdering of the concrete at the surface. It is primarily caused by the slow disintegration of a weak top layer of concrete. Foot traffic, cars, and yes, even cleaning can enhance the problem.
There are many reasons for this weakened layer of concrete. It can range from poor mixing of the concrete at the plant, excess clay or silt in the concrete mix, old age, or even insufficient curing at the surface. The most common reason, however, is excess bleed water at the surface during the finishing process.
If there is too much water in the concrete mix, this water will rise to the surface during the finishing process (troweling). This bleed water can carry finer particles and cement to the surface, forming a weak layer of concrete at the upper most top of the slab. This surface laitance is actually a porous layer of softer concrete that slowly breaks down, thus creating the white powdery surface. In some cases the surface can be so soft that it can easily be scratched with a sharp screwdriver or nail.
This same condition can be also be caused when water is added to the surface during the finishing process in a last ditch effort to create a smooth troweled surface.
Sweeping of the concrete never seems to get it completely clean since the surface is in a constant state of disintegration. If left untreated, this fine concrete dust can become extremely annoying as it finds its way onto the surface of cars, work benches, laundry machines, and anything else kept in the garage. It can also easily be tracked into the house on the bottom of your shoes.
How to stop a dusting garage floor
Fortunately, stopping concrete dusting of your garage floor is not a difficult process in most cases. Doing so will not only slow down or fix the dusting problem, it can also seal your concrete and protect it from further damage at the same time.
For very light dusting, a simple solution is to apply a siliconate penetrating sealer. Siliconate sealers chemically react with the concrete to form a calcium silicate barrier at the surface. This barrier not only seals the concrete, it helps to strengthen the weakened layer of laitance at the surface.
Siliconate sealers do not change the appearance of the concrete, but they will bead water and protect the concrete from road salts, freeze thaw damage, and even help resist stains. Application is easy and the only prep necessary is to clean the garage floor. You can learn more about siliconate sealers here.
Another option for light dusting would be the application of an acrylic topical sealer. These type of sealers are film forming and create a protective barrier on top of the surface. They work well at stopping concrete dusting and make the garage floor easy to clean as well. Our recommendation would be an MMA acrylic sealer.
If the dusting is a bit more extreme, but the surface isn’t so soft that you can easily scratch or gouge it with a screw driver, then a densifier would be a better solution.
Densifiers are actually a concrete hardener. They are used primarily for polishing concrete but have other uses as well, including the reduction of concrete dusting. They penetrate deep into the concrete and have a strong chemical reaction that helps to fill open pores and capillaries within it. They can actually increase the surface strength up to 40% depending on the initial condition of the concrete.
Unlike siliconate sealers, however, densifiers do not form a protective barrier at the sub surface since the molecular structure of the densifier is much smaller. Because they do such a good job of making good concrete more dense, they are sometimes mistaken for a sealer since water can sometimes bead initially after application.
Lithium based densifiers are the easiest to apply and usually the most effective. As with the siliconate sealer, all that is required is to clean the concrete before application. Densifiers will not change the look of the concrete and they are easy to apply as well.
We did a review of a densifier which we had applied to a garage floor for a family member. The concrete needed treatment that only a densifier could provide. We were very happy with results and you can read about it here.
If you like the look of your bare concrete, but you want to fix the dusting problem and seal it the best you can as well, then a two step procedure of a densifier and penetrating sealer would be the best option. This product from GhostShield would be an excellent choice.
If the surface of your concrete is soft enough to scratch with a screwdriver or your dusting is severe, then you may want to apply a floor coating such as epoxy. A properly applied coating will not only enhance the looks of your garage floor, it will last for years and provide excellent protection from the elements, including chemicals and automotive fluids.
If decide to apply a garage floor coating to a garage floor that is dusting, then grinding the concrete is required. Grinding will remove the excess laitance and layer of soft concrete at the surface. Acid etching will not effectively remove laitance. If epoxy is applied to dusting concrete that was prepped only with acid etching, the epoxy will peel up at a later date, exposing a thin layer of concrete dust on the bottom of the epoxy.
You will need to use an aggressive concrete grinder in order to remove the upper layer of concrete. If the garage floor coating is professionally installed, the contractor may even use a shot blaster to remove the soft layer.
Though concrete dusting can be a real nuisance in your garage, it doesn’t mean that you can’t tackle the issue with a little bit of DIY effort on your part. Unless the dusting is severe, proper cleaning of the floor and easy application of a penetrating sealer or densifier usually gets the job done. All that is required is some cleaning supplies and a pump up garden sprayer to apply.
If the dusting is severe enough that the concrete can be scratched easily, we recommend contacting a floor coating contractor if you do not feel comfortable with grinding the concrete or installing an epoxy coating yourself.
Finally, it’s always a good idea to contact a quality concrete floor coating and sealing vendor to ask questions if you are unsure. Home improvement centers generally are not well educated on such topics and most do not carry the proper products to use. Vendors who specialize in concrete coating and sealing products, on the other hand, are extremely knowledgeable and can help you to successfully stop concrete dusting of your garage floor.