Decorative portland cement, especially white cement, plays a very important aesthetic role in the surface of the building.
It is very important for white portland cement production to select various raw materials carefully and adopt special production technology to avoid pollution which has adverse effect on whiteness in production. Generally, the grey of portland cement is mainly caused by the composition of iron oxide (Fe2O3), so the content of iron oxide in white portland cement should be reduced as much as possible. The raw materials suitable for white cement production are white haze or limestone and white porcelain clay, because their iron oxide content is very low. Among the four main miners of portland cement, only calcium ferrialuminate phase has obvious color, which makes portland cement have its own gray color. The composition of chromium oxide and magnesium oxide also has significant influence on the color of portland cement.
Most of the decorative products widely used in the construction industry are based on white and colorful portland cement. It includes cement paint, which is a kind of paint based on portland cement mixed with pigments, fillers, accelerators, waterproof materials and other suitable additives. The finished cement paint is dry powder and mixed with water before use. White portland cement is generally used for light paint, while gray portland cement is used for dark paint instead of white cement as basic material. Powdery cement paint is controlled by British standard BS4764. According to British Standard BS 12, this product must consist mainly of portland cement, pigments and fillers.
