Silane water repellents for concrete
Silane is a penetrating waterproofing compound that soaks deep into the capillaries of concrete, forming a hydrophobic layer inside that makes the surface water-repellent, resists mold and mildew and limits corrosive salts, while still allowing moisture vapor to escape.
Not every surface is suitable for a sealed membrane. Exposed concrete facades, ports and wharves, breathable brick walls and parking structures often need an invisible waterproofing solution that does not change the color or texture of the material. Silane meets exactly this requirement.
How silane works
Silane molecules are very small and can penetrate 5 to 10 mm into concrete depending on its density. There, the silane reacts with moisture and minerals in the concrete to form a polysiloxane network bonded to the capillary walls. Liquid water is repelled, while water vapor can still pass through.
- Forms no film, so it does not peel over time.
- Preserves the natural color and texture of the concrete.
- Reduces water absorption by more than 80% compared with untreated concrete.
- Limits chloride ion ingress, protecting the reinforcing steel.
Silane, siloxane and blends
High-concentration pure silane offers the best penetration and is suited to dense concrete and coastal structures. Siloxane has larger molecules and is suited to porous materials such as fired brick and natural stone. Silane-siloxane blends balance penetration with surface performance and are widely used on building facades.
Solvent-based and water-based
Solvent-based products penetrate quickly but have an odor and require ventilation. Water-based emulsion or cream products are more environmentally friendly; creams cling well to vertical surfaces, run less and provide longer contact time.
Application guidelines
- Concrete should be at least 28 days old, with a dry and clean surface.
- Repair cracks wider than 0.3 mm before treatment.
- Spray or roll on using a wet-on-wet method until the surface is saturated.
- Avoid application when rain is imminent or when the surface temperature is too high.
Checking effectiveness
After a few days, effectiveness can be checked by spraying water on the surface: water beading up and rolling off is a sign that the silane is working. A Karsten tube test provides a more quantitative measurement of water absorption.
Silane treatment typically remains effective for 10 to 15 years depending on exposure conditions. The treated surface can still be painted with a breathable water-based paint if a color change is needed, but test adhesion on a small area first. When effectiveness declines, simply clean the surface and spray a maintenance coat without having to retreat the entire surface.
Contact AMS Vietnam for advice on the right silane product for the concrete and building materials on your project.
