Acid rain usually refers to acidic precipitation with a pH value below 5.6. Its main components, such as sulfuric acid and nitric acid, are highly corrosive. When acid rain comes into contact with compound pigment multi-colored powder for bitumen paved roads, the acid solution will penetrate into the interface between the color powder and asphalt and into the color powder particles. The metal oxide pigments in the color powder (such as red iron oxide and green chromium oxide) are prone to chemical reactions with acids, resulting in the destruction of the molecular structure of the pigment, which leads to fading. In addition, acid rain will corrode some components in the asphalt, reduce the adhesion between asphalt and color powder, accelerate the peeling of color powder, and make the color of the road surface mottled and uneven. With the continuous erosion of acid rain, the protective function of the color powder of the road surface is weakened, affecting the appearance and safety of the road.
Ultraviolet radiation is an important factor that causes the aging of compound pigment multi-colored powder for bitumen paved roads. Ultraviolet rays with shorter wavelengths have high energy and can break the chemical bonds of the pigment molecules in the color powder, triggering the photodegradation reaction of the pigment. Especially for organic pigments, their chromophores are destroyed under ultraviolet irradiation, and the color gradually fades. At the same time, ultraviolet rays will cause asphalt to undergo oxidation reactions, produce polar groups such as carbonyl and carboxyl, make asphalt hard and brittle, and reduce its ability to wrap and bond color powder. After long-term exposure to ultraviolet rays, the color powder particles are gradually exposed, not only losing color, but also easily worn by external forces such as wind and sand, shortening the service life of the road color coating.
In the actual environment, acid rain and ultraviolet rays often act at the same time, and the synergistic effect of the two will significantly aggravate the erosion of color powder. After acid rain destroys the surface structure of color powder, it will enhance the material's ability to absorb ultraviolet rays and accelerate the photoaging process; and the aging of materials caused by ultraviolet rays will make the color powder more susceptible to chemical erosion by acid rain. This vicious cycle will cause the color powder of the road surface to fail quickly, resulting in serious fading and peeling problems, greatly reducing the durability and aesthetics of the color asphalt pavement.
In order to cope with climate erosion, color powder and asphalt can be modified. In terms of color powder, inorganic pigments that are acid-resistant, alkali-resistant, and UV-resistant or organic pigments that have been surface-treated are selected, such as titanium dioxide coating of pigment particles to enhance their UV resistance and acid-base resistance. In asphalt modification, antioxidants, UV absorbers and other additives are added to improve the aging resistance of asphalt and enhance the adhesion to color powder. For example, adding nano-silicon dioxide particles to asphalt can form a dense protective layer that effectively blocks acid rain and ultraviolet erosion.
The premixing method is used to fully mix the color powder with asphalt, so that the color powder can be evenly dispersed in the asphalt, forming a more stable structure and reducing the impact of external erosion. During the pavement laying process, the appropriate compaction degree and construction temperature are controlled to ensure that the asphalt and the color powder are closely combined to improve the compactness of the pavement. In addition, spraying a protective coating with acid rain and UV resistance functions on the surface of the colored asphalt pavement, such as a water-based polyurethane coating, can form a physical barrier on the pavement surface and further improve the protective performance.
Use spectral analysis technology to detect the color change of the color powder, and use sensors to monitor the physical performance parameters of the pavement (such as hardness and bonding strength) to detect early signs of erosion damage in a timely manner. Based on the monitoring data, a scientific maintenance plan is formulated, such as regular cleaning of the pavement, re-spraying of the protective coating, etc., to repair before the erosion has caused serious damage, and extend the service life of the colored asphalt pavement.
With the improvement of environmental protection requirements, the research and development of eco-friendly protective technology has become the future direction. Develop degradable protective coating materials to reduce the pollution of chemical substances to the environment; explore the use of natural ingredients such as plant extracts as anti-erosion additives to improve the protective performance of color powder. At the same time, strengthen interdisciplinary research, apply bionic principles to color powder protection design, imitate the structure and characteristics of erosion-resistant materials in nature, and provide new ideas and methods for the protection of compound pigment multi-colored powder for bitumen paved roads.
