1. Silane / Silane-Siloxane Concrete Sealers – Silanes have small molecules and are slow reacting allowing them to penetrate the concrete and go deep into the concrete. The concrete must be thoroughly saturated with a high solid Silane to be adequately sealed. The main problem in the industry is that the products are used with too low of a spread ratio and do not have a high solid (active ingredient) content. A very heavy saturation of the surface is required to get an adequate seal. They work very well for very porous substrates and for protecting vertical surfaces from wind-driven rain. They protect against mold and mildew and efflorescence. If they are applied correctly, they are the most costly of the penetrating sealers. Multiple applications are necessary. Silane or silane-siloxane sealers cannot be used on newly placed concrete. Surfaces must be 28 days ole and/or fully cured before using them. (Link to SealGreen Brick and Stone Sealer) (Link to SealGreen Brick and Stone Sealer)
2. Silicate Concrete Sealers - These are chemically reactive, penetrating concrete sealers that permanently bind to the silicates in the concrete. The concrete must be removed in order to remove the sealer. Silicates are easy and inexpensive to make. There is no standard and the quality of the sealer is very dependent on the manufacturer and their ethics. Silicates have the smallest molecules of the penetrating sealers and as such go very deep into the concrete. They are normally referred to as densifiers or hardeners. In order to seal the surface, you must build the sealer from the bottom of the concrete to the top. This requires a lot of product and many applications – sometimes even working the product into the concrete. Most installers do not apply the product properly so an adequate seal is not achieved. Silicate sealers are the lower price sealers of the penetrating sealers and the life of the sealer is short. They cannot be used as a cure and seal on new concrete because they do not maintain the required moisture and temperatures. They can be used on new concrete to densify, harden or strengthen the concrete.
3. Siliconate Sealers – Siliconate sealers are versatile sealers that can be used on almost any concrete surface. These sealers work by creating a permanent chemical change in the concrete. There is a chemical reaction inside the open pores of the concrete that creates a gel, which hardens, chemically bonding to the concrete and creating a “plug” in the pore. Siliconates have larger molecules and react quickly which effectively seals the surface of the concrete offering more surface protection while maintaining the breathability of the concrete. Siliconate sealers are the perfect choice when your primary objectives are reducing moisture absorption, reducing freeze/thaw damage and stain penetration. Siliconates dry within the concrete and do not change the appearance or the texture of the concrete surface. They can also be used as a cure for freshly poured concrete. They cure by retarding moisture while allowing the concrete to breath. Siliconates have multiple applications – they can be used on bare concrete walls or stucco to keep moisture from soaking through paint and to allow the paint to last longer. Siliconates can be used on sidewalks, driveways, parking lots, porches, pool decks, retaining walls, patios, etc. to reduce cracking, staining, and freeze/thaw damage. Overall, this is the sealer we believe works the best for the majority of applications on broom finish or trowel finish concrete. (Link to SealGreen Concrete Sealer)
These sealers are widely used in the industry and are primarily solvent-based
products. These sealers can become brittle and delaminate with age. They also
have a tendency to turn yellow in the light. They come in a variety of solids
(the higher the solids, the longer the sealer will last), some come with UV
protection, and they even come in a water-based formulation. The solvent-based
formulas emit high levels of VOCs (volatile organic compounds) and will
probably be off the market within a short time due to clean air and clean water
standards. Acrylic sealers form a film on top of the concrete and thus protect
it from water absorption. Two light coats of sealer about 12 hours apart are
recommended by the manufacturer for maximum longevity. However, homeowners need
to be aware that acrylic sealers need to be recoated every 18 to 24 months and sometimes
sooner depending on weather, wear and tear, and exposure to the sun. They are
used to bring color, shine and the “wet look” to decorative concrete. It is
important to allow adequate drying time before and between applications of these
sealers – at least 8 hours between each step to avoid encapsulating moisture.
5. Epoxy and Urethane Concrete Sealers – These sealers provide high chemical and abrasion resistance and provide deep color and gloss to decorative concrete. Many of the epoxies on the market are two-part (you must mix Part A and Part B) and then have a limited usable life (usually about an hour). They can be difficult for an inexperienced homeowner to install on their own and are difficult to remove if the installation goes awry. They are usually expensive but they go a long way – up to 400 square feet per gallon. Some epoxies offer protection from sulfuric acid, brake fluid, gasoline, and/or high heat, other offer humidity mitigation. Always look at the ASTM test data on each particular product to determine its resistance and durability and intended use. (Link to SealGreen Epoxy and Poly Sealers)
There are other types of sealers available on the market but most fit into one of these categories. If in doubt – call and talk to a knowledgeable person in the sealing industry to help you decide which sealer to use.