Is Moisture a Problem for Polished Concrete?
Water can be a real washout for concrete. Here’s what moisture in concrete can cause when it’s present before floors are polished.
Key Takeaways:
- Moisture levels in concrete can cause problems while polishing a floor
- Sealants, densifiers, and dyes may not work as well
- It can also cause floor damage
- Checking the moisture levels before polishing is essential
A polished floor is the bee’s knees, but trying to buff a soaked surface can be a real stinger. Polish is great at resisting water after the job is done, but that’s only half the story. Contractors often have to wrestle with moisture levels in concrete to prepare a surface for further work.
Where there’s moisture, there’s a laundry list of potentially serious problems. Any of these can interfere with the polishing process and detract from the final wow factor of a floor. Here are some problems caused by moisture in concrete, what your contractor will look for, and what they might do to solve them!
Discoloration and mold formation
Concrete is porous. This is essentially good as it helps transport gases and water vapor and aids the curing process. It’s also potentially bad because mold spores see pores as open doors (say that ten times fast). These little lodgers are microscopic, but their damage potential is massive.
Seeing dark green or black spots on a concrete floor can mean mold is already there. All mold needs are high humidity, a thin coating of surface moisture, and/or a buffet of dust or debris that has accumulated on a surface, and it starts multiplying like crazy. It then starts producing acid, which means even more stress and stains on your concrete.
These blemishes will show through the polished finish if they’re not dealt with beforehand. The good news is that thorough cleaning, adjustment of relative humidity, and improved ventilation are often enough to deal with concrete mold and its marks.
How concrete gets salty
Another thing mold loves to eat is salt. Some buildup on concrete floors can come from efflorescence, a salt-producing process caused by water vapor or elevated alkalinity that can complicate things for bonding and adhesives.
The powdery deposits created by efflorescence can vary in color depending on the type of salts in the moisture or in the concrete itself. Soluble salt is sometimes added to blends, though it’s a controversial practice. You may see white efflorescence but also gray, green, or yellow.
Efflorescence can be a tough customer that can take out even epoxy or polyurethane flooring. The issue can sometimes be solved by using more water to give it a good scrubbing, applying a vapor retarder, or using a waterproofing admixture. Alternatively, it may require using a weak acidic solution or re-emulsifying or stripping the original sealer for a closer look before polishing can begin.
How dust and cracks combine with moisture in concrete
Cracked concrete has several causes, such as wear and tear, excessive load bearing, or the freeze/thaw cycle. Cracks are another entry point for moisture, and they can be solved by adding a concrete filler like epoxy.
By now, you know that dust isn’t harmless because it’s one of mold’s favorite foods. There’s a second kind of dust that may be present as well. This is silica dust, a crystalline byproduct of concrete cutting or drilling. It can also be caused by moisture damage or the floor being slowly ground down by foot traffic or moving equipment.
On its own, this dust can choke equipment and people, taking both out of commission. Mixed with moisture, it can form an abrasive paste that will need to be cleaned off before floor polishing starts. This paste can dry out given enough time, creating yet another surface layer problem that may require some tough buffing.
Moisture can do densifiers dirty
Densifiers are liquid chemical coatings added to damaged and fragile concrete. They go in through the top layer and form crystalline structures that strengthen underlying bonds and give the concrete’s surface a stronger top layer. This can further increase its water resistance unless a lot of moisture is already present.
If that’s the case, the densifier’s effect will be reduced as it struggles to enter, a drawback that can also be caused by cold temperatures or high humidity. Don’t let all these moisture issues get you down! You don’t have to skip polished concrete due to water woes because the pros have a few ways of removing it.
How contractors get rid of moisture in concrete
Sometimes, it’s necessary to bring out the big guns to tackle moisture in concrete. Few methods are more effective than just removing the layer that’s holding the water! Here are some solutions to get that job done:
- Shot blasting – A powerfully abrasive process that blasts away the moisture-damaged layers using rapidly ejected pellets of steel, metal, or other materials.
- Hydroblasting – Effectively the same as shot blasting, only using powerful jets of water to smooth the surface. The water is often mixed with an abrasive material.
- Grinding – Diamond-coated pads slowly grind the concrete down using multiple passes.
- Milling or scarifying – These also remove damaged top layers using saws and carbide cutters instead of diamonds.
All those processes are available through Concreate and can remove moisture, increasing the chances of successful applications of stains, dyes, and densifiers. From there, it should be smooth sailing to a polished and watertight concrete floor.
Just be sure it’s the right choice for your site based on what it’s used for and who’s using it. You’ll be saving energy by increasing ambient light while enjoying a floor that’s as clean as it is shiny.
Contact Concreate with any polishing questions
At Concreate, we bring decades of experience to polishing jobs and many other concrete-based services like staining and surface preparation. It’s our goal to help customers and contractors better understand concrete, so the pros know how to work and the public knows what to expect. Visit our contact page to ask anything concrete-related or discuss your project needs!