What are concrete sealers used for?
Concrete sealers are applied to concrete to protect it from surface damage, corrosion and staining as much as possible.
Sealers also close the pores on the surface to reduce the absorption of water and mineral salts that damage the surface or form an impermeable layer that prevents such materials to penetrate.
Investigations by the main international concrete authorities such as American Concrete Institute, Portland Cement Association and National Ready Mix Concrete, among others, confirm that the majority of concrete damage is due to the penetration of moisture on the surface.
The most common form of concrete damage is scaling of the surface by freezing or thawing, as the surface expands and contracts.
Other common forms of concrete damage include alkali-silica reaction (ASR), chemical intrusion and corrosion of steel reinforcements in reinforced concrete.
The basic types of concrete sealers
In recent decades, attempts to protect concrete have included sealers ranging from wax to linseed oil. Today, high-quality concrete sealers can minimize surface moisture up to 99%. There are two main categories of sealers: topical sealers (coatings) and penetrating (reactive) sealers.
Surface sealers can provide visual enhancements and topical protection against stains and chemicals. They require a dry, clean surface during application to gain adhesion.
Topical sealers can alter the coefficient of friction that can cause substrates to become slippery when wet, a condition that can be remedied by adding anti-slip materials.
Penetrating sealers can be applied to dry or wet surfaces and must properly match the porosity of the substrate to effectively penetrate the surface and react.
The chemical reaction binds the active ingredients within the substrate that minimizes surface moisture. Penetrating sealers generally do not significantly modify the appearance or traction of the substrate.
Main Chemicals of Commonly Used Concrete Sealers
Acrylic resins create a film-forming membrane on the surface of the substrate. Available in both water-based and solvent-based formulations, they are affordable and generally easy to apply.
They are well known for increasing perceived visual improvement (sometimes described as a “wet look”) and can provide good UV protection for colour substrates.
Despite being the smoothest and least durable of the major sealer categories, price and convenience make acrylic resins a popular choice for decorative concrete such as stamped concrete and exposed aggregate.
Acrylic resins are also commonly used as curing agents for new concrete, and many meet ASTM C309.
Epoxy / urethane systems:
Epoxy / urethane systems are also film-forming membranes.
They share many of the same characteristics as acrylics, but performance levels and life are higher and proportionately more expensive due to more complex installation requirements.
Epoxy / urethane systems are generally applied only to fully cured existing concrete, although certain epoxy products may meet ASTM C309.
Silane is the smallest molecular compound of commonly available penetrating sealers.
Chemically, silane forms a covalent bond within porous masonry that coagulates surface pores.
Silane is known to be hydrophobic and oleophobic and will only wear if the concrete surface is worn. Known for its low viscosity, silane is often used to seal dense concrete, such as parking platforms, concrete facades and dense brick.
Silane is generally applied only to fully cured existing concrete.
Silicates are another small molecular compound ranging from premium lithium silicates to more economic sodium silicates.
Chemically, silicates form calcium hydrate and silicate crystals that can densify concrete surfaces and burnish/polish to develop a glossy finish.
Silicates are known to be hydrophobic and oleophobic and will only wear if the concrete surface is worn. Known for their crystallization, silicates are often used to polish concrete floors at large industrial or commercial facilities.
Silicates can be applied to new and existing concrete, although they do not meet ASTM C309 as a curing agent.
Siliconates are molecular compounds of moderate size. Chemically, siliconates form a repellent cross-linking membrane barrier within the surface of porous concrete and other masonry.
Siliconates are known to be hydrophobic and oleophobic and will only wear if the concrete surface is worn.
Known for their extreme water and stain repellency, siliconates are often used to seal exterior concrete such as roads and driveways, sloping walls, porous brick and porous stone.
Siliconates and organic siliconates have also proven effectiveness as curing agents for new concrete and certain products can meet ASTM C309.
Siloxane is the largest molecular compound of commonly available penetrating sealers.
Although not highly reactive, siloxane chemically forms a bond within porous masonry that coagulates surface pores.
Siloxane is known to be hydrophobic. Known for its large molecular structure, siloxane is often used to seal exterior concrete, porous concrete blocks and porous bricks.
Siloxane is generally applied only to fully cured existing concrete.
In short, all major concrete sealer chemistries can have valuable and practical applications.
Topical sealers generally require higher application and maintenance standards, but the decorative appeal and their stains and chemical resistance can make them a superior choice for many applications.
Penetrating sealers must be combined with the porosity of the substrate for low maintenance water repellency and long lasting freeze/thaw protection.
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