Attack of the Road Salts!
Parking garages in this region are attacked by road salts and water throughout much of the year. The cost to repair deteriorated concrete can be quite high and the project can cause significant inconvenience to garage users. So, as part of a parking garage restoration project, we recommend and our clients tend to include, application of a vehicular-traffic-bearing membrane on the structural slabs to help protect their investment and extend the service life of the garage.
There are two basic classes of products commonly used to protect garage slabs, one of which is penetrating sealers. Penetrating sealers include materials such as silanes and siloxanes, which are silicone-based water repellants. These compounds penetrate into the concrete and react with the silica to create a water repellant barrier that also retards chloride migration.
Penetrating sealers are breathable so they do not create a vapor barrier and are relatively inexpensive. However, they do not seal cracks and require frequent reapplication as their effectiveness decreases with wear and time. These materials usually need to be renewed on a three to five year schedule.
The other class is traffic-bearing membranes, which are liquid-applied materials in several layers of cementitious, epoxy, or urethane compounds. These systems are all relatively thick (up to about 90 mils) and are designed with the properties needed to withstand the destructive forces imposed by vehicles tires.
Cementitious products are generally robust, breathable, and well suited for on-grade or elevated slabs, especially those with steel decking supports.
Epoxies are very durable and offer outstanding abrasion resistance, but are not breathable and are less flexible. So they are prone to cracking when slabs move/crack over time. They are well suited for on-grade slabs and areas where chemical and/or extreme wear resistance is needed.
Urethanes are softer, non-breathable, and more flexible so they have the ability to bridge cracks, which makes them ideal for elevated, reinforced concrete slabs. Some systems include an epoxy primer so that the urethane can be applied to on-grade slabs. Systems from reputable manufacturers are generally warranted for five to ten years and can remain serviceable longer, if properly maintained. Most membrane systems offer fast-cure and low-odor formulations, if the project has special requirements.
Consult your trusted restoration engineer before embarking on a garage coating project, as picking the right coating system can make the difference between a successful and not-so successful result.