White Portland cement or white ordinary Portland cement (WOPC) is similar to ordinary, gray Portland cement in all aspects except for its high degree of whiteness. Obtaining this color requires substantial modification to the method of manufacture, and because of this, it is somewhat more expensive than the gray product.
White Portland cement is used in combination with white aggregates to produce white concrete for prestige construction projects and decorative work. White concrete usually takes the form of pre-cast cladding panels, since it is not economical to use white cement for structural purposes. White Portland cement is also used in combination with inorganic pigments to produce brightly colored concretes and mortars. Ordinary cement, when used with pigments, produces colors that may be attractive, but are somewhat dull. With white cement, bright reds, yellows and greens can be readily produced. Blue concrete can also be made, at some expense. The pigments may be added at the concrete mixer. Alternatively, to guarantee repeatable color, some manufacturers supply ready-blended colored cements, using white cement as a base. The whiteness of WOPC is measured as the powdered material having a reflectance value ("L value") in excess of 85%. A particular success in the use of WOPC and added pigments is monocouche renders.
In some countries an off-white clinker, which gives a reflectance value over 70 when ground,is produced at a cost only a little over normal gray clinker. When this is blended with ground blast furnace slag (up to 60% depending on use and early strength) a cement with reflectance over 80 can be produced. The blended cement can have a production cost less than General Purpose Portland cement (gray), but normally attracts a margin as it is sold to compete with white Portland cement.