Bitumen paint has better properties than ordinary black bitumen due to the use of polymer, so that it is more resistant to heat and cold, and thus improves the performance of the asphalt layer.
Today, in many countries, they mark different sections of highways with colored asphalt,
and instead of painting, they apply such bitumen that contain various mineral pigments,
including titanium dioxide. Generally speaking,
Bitumen paint is from mixing bitumen with pigments and these pigments have two categories,
organic and chemical. Chemical pigments such as iron oxide, chromium oxide, titanium dioxide and mixed
pigments (such as cobalt blue) are suitable for bitumen paint mixtures.
These pigments are stable in all climatic conditions, but organic pigments from insects and plants are unstable to heat and
weather conditions and are unsuitable for mixing with bitumen paint. Needless to mention that the most important type of organic
pigment is azo pigment. In fact, they are a composition of aromatic hydrocarbons. Iron oxide is one
of the most common inorganic pigments and has two types, natural and synthetic.
The natural type is in the range of yellow, light brown-red, greenish-brown and bold browns
and the synthetic type is in the range of yellow and red to black and brown colors.
The bitumen paint also plays an important role in the production of the color mixture, and red iron oxide and green chromium oxide are often applicable for it. Clear colors can only be proper on pale colorless binders. Besides, these binders do not contain asphalt and have high pigmentability.
Basically, with these binders, more diverse colors can appear by using yellow, brown and black iron oxide and green chromium oxide.
Of course, as long as they have a good thermal resistance.
As a matter of fact
at temperatures above 180 ° C, yellow and black iron oxides convert to red iron oxides.
It should be noted that the mixing temperature is usually more than 180 degrees Celsius.
Zinc ferrite products with high thermal resistance are also applicable in yellow and a mixture
of manganese and iron oxides for brown and gray colors.
It’s essential to know that the thermal resistance of pigments such as red iron oxide,
green chromium oxide, and titanium dioxide is suitable for the production of colored asphalt mixtures in road construction.
Titanium dioxide is one of the most common inorganic pigments with a high refractive index
that produces white color and its pigments are morphologically in the form of anatase and rutile.