Chemical densifiers or sealers are silicate-based products (most commonly sodium silicate). When applied to concrete or masonry react with the calcium hydroxide within the concrete to reduce the porosity and permeability of the concrete matrix. This serves to increase the hardness and chemical resistance which increases the service life of the concrete surface. They reduce the porosity or permeability of the concrete structure by filling in some of the pores and capillaries within its structure. This improves its overall physical strength, hardness, durability and abrasion resistance.
Types of Densifiers
Use densifiers on driveways, sidewalks and garage floors to protect them against frost and salt damage which produces concrete spalling. At the same time, they increase the resistance to stains, acids, alkalis, moisture, mold and mildew. Additionally, use to cure wet and damp basement walls and floors. In this application, they act as an internal moisture barrier to prevent hydrostatic moisture from entering the basement area. The sealers will also significantly reduce radon levels in basements. The EPA states that “Exposure to radon in the home is responsible for an estimated 20,000 lung cancer deaths each year. Radon is a health hazard with a simple solution.”
Sodium silicate densifiers or sealers such as Concrete Sealer X-1 or Concrete Sealer X-2 are very easy to apply. They are environmentally friendly, non-toxic, non-flammable and do not contain chemical solvents or release any VOC or noxious fumes. They leave a natural or invisible finish (no sheen). After application, they are UV resistant, non-yellowing, breathable and the surface will not be slippery. The sealers are not repellent coatings so the concrete is paintable. After it has been sealed, it has increased paint adhesion because the sealer neutralizes the alkalis in the concrete preventing saponification of the paint. Additionally, apply adhesives and epoxy coatings over the sealed concrete with no adverse effects.
Application of Densifiers
Apply to a fully cured concrete surface (which is normally 28 days after it has been poured). Use either a medium nap paint roller (3/8″ nap) or low pressure or pump-up sprayer. The surface is completely wet out with the sealer to make it appear visibly wet. However, do not over apply the product, it should not puddle or accumulate in low lying areas (mop up any excess with a clean dry towel). Wait for 2 to 4 hours and then apply the second application use the same process.
Apply during good weather at 40 to 80 degrees F with no rain in the forecast for at least 48 hours. The sealer will start curing within the concrete structure immediately. Curing takes up to 28 days while it fully reacts with the free lime (calcium hydroxide) within the concrete. Traffic during this time will not cause any damage to the sealer because the reaction is an internal one. The coverage rate is typically 300 square feet per gallon for each application. This can vary depending on the porosity of the concrete and it can be as low as 200sf or as high as 400sf. Typically, a 5 gallon pail will cover 750 square feet of concrete with two applications.