How To Prepare Concrete Floors For Topcoats
There are three things to address before applying a topcoat to any concrete floor… Contaminants, moisture, and pH. Contaminants can be anything from dust and dirt to grease, mold, mildew and other topical sealants. These need to be removed before any topical sealant can properly adhere to the concrete.
Dust and dirt can be easily removed by pressure washing or extracting the dirt away with an extractor machine, like most carpet cleaning companies use. Extractor machines work great indoors because they are self contained, meaning that all the water is sprayed in a contained wand and they have a vacuum system attached to the wand to remove the contaminants. Mold and mildew might require a specialty cleaner in conjunction with the pressure washing / extractor process. Grease is more difficult to remove but there are plenty of products that can be purchased to help leech the oils out of the slab. Most poultice based products take at least 24 hours to be effective and might take more than one application. There are products that can be used same day as pressure washing but are usually more chemical based.
Sealant removal can be a little tricky if you don’t have the right tools. Most topical sealant can be removed with floor strippers but unfortunately a lot of these products are toxic and high in VOCs. There is a great soy based strippers and other products out there that work just as well but need to be ordered online. An orbital floor machine equipped with black stripper pads also works great. The floors need to be rinsed well after any sort of stripping to remove the stripper and sealant residue. Bead blasting is a great alternative for stripping a concrete floor and preparing it for the topcoat application.
Making sure the slab is completely dry and at the proper pH is extremely important before applying a topcoat. If there is residual moisture in the slab or the pH is too high the topcoat will delaminate. You can test the pH of the slab using de-ionized water and pH test strips. A moisture test kit usually consists of a hand held devise with two probes that need to be inserted into the slab. This devise tests the conductivity of the concrete due to moisture.
The pH of new concrete will be approximately 12 to 13 mostly due to calcium hydroxide, which is a normal by-product of concrete hydration. As the slab reacts with carbon dioxide in air, the pH of the surface gradually is reduced to about 8.0 through a process called carbonation. A concrete slab that is carbonated and ready for topcoat application should have a pH of about 8.0, which means the surface of the concrete has had minimal moisture vapor movement. Excessive moisture vapor movement will bring additional hydroxides (alkalis) to the surface and will cause the pH level to increase. Salts that work their way up from the earth have a tendency to destroy satisfactory bonding to topcoats by sheer physical displacement.
Moisture from the cleaning process can delay the topcoat application and create a lot of extra labor costs due to travel time to the site for testing. Using Creto DPS eliminates many of these problems. Creto DPS can be applied after the cleaning process to permanently seal the concrete and prevent salts and other minerals from leeching up from the earth below. As the Creto DPS cures, it pushes out any residual moisture from the concrete and leaves the slab pH balanced and ready for topcoat application. Creto DPS application is easy, apply the sealer to the concrete and allow to dwell for 30 minutes, continually moving the sealer from areas that are puddled to areas that are more thirsty. After 30 minutes, remove the excess sealer by hosing off the area or shop vacuuming up the excess sealer, and then mopping the floor with water. Creto DPS can increase topcoat bonding ability by 300% and will extend the longevity of your investment.
There are many different topcoats on the market today and it might be difficult to choose which one is perfect for your situation. The traditional epoxy topcoats are the standard in the industry and have great chemical and abrasion resistance. Urethane topcoats can be used with an epoxy base coat to give added layer of protection. Urethane topcoats are usually non-yellowing and can be purchased in high gloss or matte finishes. Polyaspartic topcoats are by far the most durable topcoats and are non-yellowing as well. They can be a little tricky to apply because of the short pot life but this can be to your advantage when curing time is an issue. These topcoat are extremely hard and cannot be removed with chemical strippers, but have to be removed by diamond grinding or bead blasting. Creto also offers a water based topical sealant named Creto Topseal. Creto Topseal is a great sealer that leaves a natural look to the substrate while leaving the surface completely hydrophobic.
Here are links to some of the products I personally use and please contact us if you have any questions about our Creto products.