Is it a Sealer or Water Repellant?

Like most markets, the concrete industry has developed its own terminology, some of which can be contradictory and confusing. Many terms are subject to certain industry specifications, such as concrete cures (ASTM C 309) that clearly define what they are. But other terms are less clearly defined and open to individual interpretation.

This is particularly true amongst the category of penetrating products which are often referred to as penetrating “sealers”. There isn’t an ASTM performance specification that defines what a product must do in order to be called a sealer. As a result, many different types of chemistries are frequently referred to as “sealers“.

Water repellants are effective at preventing the absorption of water.

Oils, greases and other household and environmental contaminants can stain unsealed concrete.

What does it mean to seal concrete? There isn’t a uniformity of opinion about that. Most would agree that concrete must not absorb water in order to be considered “sealed”. But what about other liquids? A water repellant surface might still absorb solvents, greases and oils. A water repellant surface might still be stained by food, beverages, fertilizers, etc. Would you expect a concrete sealer to provide protection from staining, or absorption of liquids that aren’t water based?

If your answer is no, then lots of chemistries qualify as sealers, including many penetrating products (those that leave no surface film) based upon silicates, silicones, silanes, siloxanes, linseed oil, etc. But if you expect a concrete sealer to do more than prevent water absorption, then you’ve made a distinction between penetrating water repellants and film forming sealers. If that’s the case, all film forming sealers are also water repellants but not all penetrating water repellants are sealers.

Over the years, the terms “sealer” and “water repellant” have been used interchangeably. The accuracy of that comparison will depend entirely upon your expectations of what protection a sealer should do. Penetrating chemistries can have very attractive qualities. As water repellants they can provide long lasting, highly effective protection against freeze/thaw damage and chloride ion absorption. But without a film forming component, penetrating water repellants do not offer protection against a wide array of common household and environmental contaminants. For additional protection from staining and solvent based contaminants, use a film forming sealer.

Understanding these terms and how they impact product performance is the first step to choosing a product that meets your needs and expectations.

ChemMasters penetrating waterproofers include:

ChemMasters film forming sealers include: