Sealants History

Brief history of penetrating concrete sealers
The history of silicate concrete sealers goes back to World War II, when they were used to strengthen quickly poured military runways. Afterwards, the Army Corps of Engineers adopted the sealers for the preservation of concrete dams and bridges. As technology advanced, the function of penetrating concrete sealers expanded to waterproofing, damp proofing, and conditioning concrete for painting.

During the last decade, penetrating concrete sealers became widely used in the US and abroad, be it the Disney World or the Sydney Opera House. Many architects specify them for major buildings. Penetrating concrete sealers have been successfully used on thousands of concrete structures and buildings. Special sealers have been also developed for bricks and stones. They protect historical monuments against deterioration and acid rain.

Common types of concrete sealers
Wax or chemical sealers
Used as curing agents on green concrete and to keep surfaces clean during construction. Meant as temporary only. Leave a film, which makes the surface unsuitable for paints or tile adhesives. Chemical sealers require special precautions due to hazardous fumes. (A light "cure & seal" application of RadonSeal Standard also retards concrete hydration but does not emit VOCs and leaves the concrete paintable.)
Waterproofing concrete paints, surface sealants, or coatings
Interior or exterior. Crack and peel, particularly where needed - efflorescence or water pressure lift the paint film. Attacked by alkalis from the concrete (saponification). Water vapor (gas) and radon pass through. Susceptible to wear and abrasion. High maintenance costs.
Crystalline sealers
Deposit tiny silicate crystals into the pores in concrete, which expand on contact with water and thus waterproof. In the absence of liquid water, they do not seal against water vapor or radon. The crystals get eventually pushed out to the surface. Repeated applications required.
Cementitious slurry sealers
Well-proven for stopping water seepage through leaking concrete walls. Troweled on the surface. The layer contains crystals that expand on contact with water. The "cold joint" with the old concrete is susceptible to alkalis attack, efflorescence, and hydrostatic pressure, causing cracking and separation. Not designed to stop water vapor or radon. As the crystals get pushed out over time, it loses its waterproofing property. (Then, it can be sealed and bonded to the old concrete with RadonSeal.)
Silane sealers
Leave a thin unpaintable film on the surface, which repels rainwater and "beads". But the film tends to yellow and soon disintegrates due to UV-rays. Contain chemical solvents. Regular re-application is needed.
Siloxane sealers
Form a water-repellant elastomeric membrane, which "beads" water but is unpaintable and slippery when wet. Suitable for low-grade or light-weight concretes, porous materials, masonry, and stones. Water vapor and radon pass through. Re-application every several years.
Silicate sealers
Penetrate into the concrete and react with lime and alkalis to seal the capillaries. Permanent, no re-application needed. Bond, strengthen, preserve, and waterproof concrete as well as masonry with alkalis.