Efflorescence is a hazy white residue which occurs naturally on the surface of pavers, hollow/solid blocks, and other concrete products. It occurs when water-soluble salts within the product migrate to the surface and react with carbon dioxide to form calcium carbonate. This is the substance that remains visible on the surface of the products. Efflorescence may be visible when the products are installed or may appear later, seemingly at random.But it is not a product defect and the condition will usually correct itself with time and exposure to the elements. Efflorescence can be cleaned with commercially available cleaners formulated specifically for concrete products. Please refer ‘Managing Efflorescence on Concrete Pavers’ from the Interlocking Concrete Pavement Institute, USA.