One of the most compelling reasons to use a concrete sealer is to help improve the water resistance of the slab. While many manufacturers and distributors claim their products will waterproof your concrete, there is actually no way to guarantee this. If you read about such a guarantee, the company is not being entirely honest with you. Certain products offer better odds of water resistance, but no product can absolutely guarantee that their product will entirely waterproof your concrete for life.
Once you ignore the grandiose claims of most companies, you can start to figure out which type of concrete sealer offers the best level of protection from water. There are two types of sealers: topical and penetrating. The topical sealers will leave a film on the surface of the concrete, but it will not give your concrete as much protection from water and other moisture. For one, water can seep into the material from underneath, traveling through the concrete to cause the protective films to bubble and flake. These surface sealers are more like raincoats for your concrete, offering only minimal protection.
The better option to improve water resistance would be the penetrating concrere sealers. Silanes, siloxanes, silane/siloxanes, siliconates and silicate/siliconates will all function to lock out water and other harmful moisture. Once your concrete is protected from excessive water damage, you don’t have to worry about problems like mold and mildew build-up, as well as the dampness and mustiness that can plague unprotected basements. Increased water resistance also improves the structural integrity of the concrete, as water can leech from the material vital minerals crucial to its strength and durability. If water damage is something you want to prevent, you should use a penetrating sealer, which gives you the most comprehensive protection.
Our Take: By using a penetrating, impregnating sealer that densifies and hardens concrete and also provides a hydrophobic surface barrier you can ensure a fully waterproofed substrate. One of our favorite concrete waterproofers is Lithi-Tek 9500. This sealer is an invisible, penetrating concrete sealer that will not only densify concrete, but it will waterproof and help to prevent deleterious organic growth.