Use of asphalt:
It is mainly used as infrastructure materials, raw materials and fuel, and its application scope is such as transportation (roads, railways, aviation, etc. ), construction, agriculture, hydraulic engineering, industry (extractive industry, manufacturing), civil engineering and other departments.
Introduction:
Types of asphalt:
1, coal tar pitch
Coal tar pitch is a by-product of coking, that is, the black substance left in the distiller after tar distillation. It is just different from refined tar in physical properties, and there is no obvious boundary. The general classification method is to specify that the softening point below 26.7℃ (vertical method) is tar and the softening point above 26.7℃ is asphalt. Coal tar pitch mainly contains anthracene, phenanthrene and pyrene which are difficult to volatilize. These substances are toxic, and the properties of coal tar pitch are different due to the different contents of these components. The change of temperature has a great influence on coal tar pitch, which is easy to crack in winter and soften in summer. It has a special smell when heated; After heating to 260℃ for 5 hours, anthracene, phenanthrene, pyrene and other components contained in it will volatilize.
2. Petroleum asphalt
Petroleum asphalt is the residue after crude oil distillation. Depending on the degree of refining, it will become liquid, semi-solid or solid at room temperature. Petroleum asphalt is black and shiny, and has high temperature sensitivity. Because it has been distilled to more than 400℃ in the production process, it contains few volatile components, but there may still be high molecular hydrocarbons that have not volatilized, which is more or less harmful to human health.
3. Natural asphalt
Natural asphalt is stored underground, and some of it forms ore beds or accumulates on the surface of the earth's crust. Most of this asphalt has undergone natural evaporation and oxidation, and generally does not contain any toxins.
Asphalt materials are divided into two categories: asphalt and tar asphalt. Asphalt is divided into natural asphalt and petroleum asphalt. Natural asphalt is the residue of oil seeping out of the surface after long-term exposure and evaporation. Petroleum asphalt is a product obtained by treating the residual oil in refined petroleum with appropriate technology. Tar asphalt is a reprocessed product of tar, which is obtained by dry distillation of organic matter such as coal and wood. The asphalt used in engineering is mostly petroleum asphalt, which is a mixture of complex hydrocarbons and their nonmetallic derivatives. Usually, the flash point of asphalt is between 240℃ and 330℃, and the ignition point is about 3℃~6℃ higher than the flash point. The construction temperature should be controlled below the flash point.