The amount of iron oxide pigments in concrete products is limited to 1-10%. Exceeding the upper limit will reduce the mechanical strength of the products. Usually 5-8% is appropriate. At the same time, iron oxide pigments do not contain lead and zinc oxides. Both compounds affect the setting time and setting strength.
Concrete products sometimes need to be cured by heat and pressure above 200°C, so black and brown iron oxides that can be converted into iron red at 180°C must be treated with thermal stability first. If used on terrazzo, the bottom layer is 2 to 3 cm thick, and the surface layer is 15 cm thick.
Iron oxide pigments such as iron red powder have outstanding weather resistance, alkali resistance, and light resistance. These functions are not compatible with other inorganic or organic pigments. Therefore, iron oxide pigments are used as paint and coloring in building materials. Such as wall decoration, artificial marble, terrazzo floor and coloring of silicate products.
