What causes concrete dusting

What causes concrete dusting

Do you have an old chalky concrete slab on your hands, but don’t know what is going on with it? Or maybe you have a fresh concrete slab and everything should be great, but the surface concrete turns to powder?

Both of these are valid questions and it is something you definitely should take a look at. Sometimes chalky concrete slab is just something that happens with time, but there are other times when it’s something caused by the working process.

Concrete dusting

Concrete is made of cement, sand, aggregates, and water. The water to cement ratio is important and of course, the cement paste that’s formed to sand and aggregates ratio as well.

You can imagine it like what can you with a drop of cement when you have a mountain of sand right? Or maybe you have tons of water and only a little of other materials. I know it’s a stupid comparison, but the problem is related.

Too much water in the concrete mix

From that, we know that the correct ratio is important for making strong concrete. If there is too much water, when we float the final surface the extra will rise on top. It’s called water bleeding most of the time.

When something like this happens, we know there is lots of water on the surface. It will also bleed some cement there and there are probably little other light minerals as well.

Overall it’s a weak surface compared to strong concrete and it will slowly start to turn to dust when you use it.

Other reasons why concrete turns to powder

Too much water isn’t the only reason. They could have made other mistakes at the concrete plant, if you live in certain climates the surface might have frozen at some point.

The problem might be insufficient curing as well. If you’re water curing the concrete, but forget to water it at first. The top of the slab is baking in the sun and fast turning light grey so there is no water to react with the cement.

Concrete plant failures could be poor mixing or poor measuring and it could cause dusting and spalling concrete. The aggregates could be poor quality.

How concrete turns to powder and how to prevent it

How to fix dusting concrete

So we should be clear about what causes concrete dusting. If you’re here more than likely you are also looking for solution for it.

How do we stop concrete dusting from happening? Most common method is probably using sealers on it.

If you think about how concrete is porous and it’s slowly turning into dust and no matter how many times you pressure wash it, it’s still dusty the easiest solution to try would be filling those pores with something and making the surface harder.

Concrete dusting solutions

Before we look at how to fix dusty concrete, let us take a look at the solutions first. Sealer might not be what you’re looking for and you might want some alternatives.

Concrete sealer

As mentioned before, a concrete dusting sealer might be the most common solution. It is easy to apply as you can do it with a paint roller and it isn’t that expensive fix.

What’s best, you can easily do this yourself. You will keep the look of concrete surface and even alter it a little with the sealer.

Concrete densifier

If a sealer isn’t enough to handle your problem, another common trick is using a concrete densifier on it before you seal it. Densifiers work by penetrating the concrete pores and forming a harder surface with chemical reaction.

It is used when polished concrete floors are made as an example. Between grinding the floor with different grids, a densifier is used on the concrete filling the pores and making the floor even more solid.

Concrete coating

Depending on the concrete, don’t forget that this is a great alternative as well. If it’s a garage floor something like epoxy or polyurethane could make a good chemical resistant surface for your slab.

Doing it like this you don’t even have to think about the dusting again, it was meant to be. You can fix your cars and other vehicles without worrying too much about oil leaks and such.

If it’s a patio or something else like that, you can hold BBQ parties at peace because they won’t be leaving a hard-to-clean mess behind. It’s an easy surface to keep clean and comes in great decorative forms.

Make a new surface

If you’re thinking of how to fix a dusty concrete driveway none of those except the sealer might look like a good alternative. There is an option to make that dusting concrete into the exposed aggregate surface.

Think about it. The surface is the problem as it’s weak. Now we can take that surface off by sandblasting or by grinding and either leave it rough and seal or polish it a bit more and use a sealer.

Anyway the problem would be solved.

Concrete dusting fix

As a final part of this article, let’s put out a step-by-step solution on how to fix it when concrete turns to powder. It will help you to see the process if you’re new to working with problems such as this.

How to fix dusty concrete

Step 1: Every good fix starts with cleaning. Our problem is concrete dusting so broom for the bigger trash on the concrete and washing it clean with a garden hose will do.

No using pressure washer as it will probably only make it worse.

Step 2: Leave the surface to dry once it’s clean.

Step 3: Use densifier on the surface. Follow the manufacturer information how to use the product. Usually you need to dilute it.

You can spray it on the surface or and broom it so there will be no puddles or use paintroller to spread it and broom it.

Leavy it to dry for as long as the manufacturer info says and reapply if the instructions tells you to do 2 coats.

Step 4: After the densifier is dry, you can apply the sealing product on the concrete. You can spray it or use paintroller to spread it.

You should do it like you would be painting the surface. Start from one end of the slab and do it in “typewriter” fashion by going from left to right and once you get to the end, go back to the left and repeat.

This way when you spread the sealer you do it on wet surface and will have nice looking sealed concrete floor in the end.

Step 5: Let it dry as long as the sealer instruction says and reapply if it says so. You know how to do it now.

Congratulations, your quest for looking for a dust sealer for concrete floors is over now and you should have solved the concrete chalking. Now you just need to remember to use the sealer as often as they recommend at the manufacturers’ label.

Also note what kind of sealer you are using so you can get it every time you need to seal the concrete.


Now you should know what causes concrete dusting and how to solve your dusty concrete floor problem. I know it can be annoying and seem hopeless when you run into this problem, but by working systematically you can solve it.

It’s also good to notice that this works on the concrete dusting problem. If there is serious spalling on the concrete, you need to fix it with a different product before applying a sealer or anything else.

Now it would depend on the type of slab you’re fixing as I would recommend different fixes for different uses. If it’s the garage floor, I’d advise fixing the spalling and coating the floor.

If it’s outside, the same fix would work on a patio. For a driveway I’d think about what will the patch look like and would I need to do some sort of decoration to hide it from the eyes of others.

You probably guess now that there are many ways to fix one type of problem. For me there is no right or wrong way to do it as I look for the end result.

In this sort of case, we want a concrete surface that won’t be turning into dust anymore. I’d start looking into what sort of benefits would I like since I have to do something about the problem anyway.

It’s also a good way not to get too annoyed about it.

Leave a Comment

Your email address will not be published. Required fields are marked *