Occasionally, some pavers may have a whitish residue upon them. The whitish colored residue is called efflorescence. Efflorescence is a natural by-product from the cement hydration process and can be found in any concrete or mortar product. Calcium oxide inside the paver reacts with water in the capillaries and forms calcium hydroxide. This seeps to the surface, and reacts with the carbon dioxide in the air to form calcium carbonate, a whitish residue. When moisture on the surface evaporates, the white efflorescence becomes visible. If efflorescence is present, it will wear off over the course of time with traffic and the elements.