A. We highly recommend applying a densifying primer before using a sealer. Concrete densifiers are penetrating, chemically reactive products. They react with calcium hydroxide, a byproduct of cement hydration, to create C-S-H (calcium-silicate-hydrate). (The same binder that results from adding water to cement and gives concrete much of its strength). The newly created C-S-H fills in the pores and capillaries of the concrete making it up to 50% stronger. By filling these voids with C-S-H, the concrete also becomes less porous and less permeable.
When choosing a densifying primer we recommend the Lithi-Tek 4500 which is a concentrated, non-water-soluble, lithium silicate based product. Lithi-Tek 4500 is economical and only needs to be applied once in the lifetime of the concrete. Since densifiers like the Lithi-Tek 4500 are not hydrophobic or salt resistant a penetrating, impregnating sealer is recommended 5-7 days after priming. This combination will ensure a stronger and water salt & stain resistant surface for years to come.
Tip: Densifying primers are only recommended for concrete (not: brick, pavers, stamped concrete, colored concrete, etc.)