1. Definition of petroleum asphalt
English name: Petroleum asphalt
Petroleum asphalt is a product of the crude oil processing process. It is black or dark brown at normal temperature. A viscous liquid, semi-solid or solid, mainly containing hydrocarbons and non-hydrocarbon derivatives soluble in trichlorethylene. Its properties and composition vary with the source of crude oil and production methods.
2. Product performance
Petroleum asphalt is the residue after crude oil distillation. Depending on the degree of refining, it becomes liquid, semi-solid or solid at room temperature. Petroleum asphalt is black and shiny and has high temperature sensitivity.
Petroleum asphalt can be classified according to the following system:
According to the production method, it is divided into: straight-run asphalt, solvent deoiled asphalt, oxidized asphalt, blended asphalt, emulsified asphalt, modified asphalt.
According to appearance, it is divided into: liquid asphalt, solid asphalt, diluent, emulsion, modified asphalt, etc.;
According to use, it is divided into: road asphalt, construction asphalt Asphalt, waterproof and moisture-proof asphalt, various special asphalts named after their uses or functions, etc.
3. Production method
(1) Distillation method: The crude oil is distilled under normal pressure to separate light fractions such as gasoline, kerosene, diesel oil, etc., and then distilled under reduced pressure (residual pressure 10~100mmHg) to separate the vacuum distillate, and when the remaining residue meets the specifications of road asphalt, asphalt products can be directly produced. The resulting asphalt is also called straight-run asphalt, which is the main method for producing road asphalt.
(2) Solvent precipitation method: Non-polar low-molecular alkane solvents have different solubilities for each component in vacuum residue oil. The difference in solubility can be used to separate the components, so it can be obtained from The solvent precipitation method is used to remove components that are detrimental to asphalt properties from the vacuum residue to produce asphalt products that meet specifications.
(3) Oxidation method: Air is blown into vacuum residual oil or deoiled asphalt at a certain range of high temperatures to change its composition and properties. The resulting product is called oxidized asphalt. Vacuum residual oil will vaporize and evaporate under the action of high temperature and blowing air, and a series of reactions such as dehydrogenation, oxidation, polymerization and condensation will occur at the same time. This is a very complex comprehensive reaction process in which multiple components interact with each other. It is not just an oxidation reaction, but it is customarily called oxidation method and oxidized asphalt. It is also called air blowing method and air blown asphalt.
(4) Blending method: The production of asphalt by the blending method initially refers to the re-blending of the four components of asphalt composed of the same crude oil in the proportion required by the quality requirements. The resulting product is called synthetic asphalt or reconstructed asphalt. . With the development of process technology, the sources of blending ingredients have expanded. For example, residues or components from primary and secondary processing of the same crude oil or different crude oils, as well as various industrial waste oils, can be used as blending components, which reduces the dependence on oil source selection in asphalt production. With the increasing shortage of crude oil suitable for making asphalt, the flexibility and economy shown by the blending method are increasingly being valued and widely used.
(5) Emulsification method: The surface tensions of asphalt and water are very different, and they are not miscible with each other at normal or high temperatures. However, when asphalt is subjected to mechanical actions such as high-speed centrifugation, shearing, and impact, it becomes particles with a particle size of 0.1 to 5 μm, and is dispersed into a water medium containing surfactants (emulsifiers-stabilizers). Due to the emulsifier It can be directionally adsorbed on the surface of asphalt particles, thereby reducing the interfacial tension between water and asphalt, allowing the asphalt particles to form a stable dispersion system in water, which is an oil-in-water emulsion. This dispersion system is brown in color, with asphalt as the dispersed phase and water as the continuous phase, and has good fluidity at room temperature. In a sense, emulsified asphalt "dilutes" the asphalt with water, thereby improving the fluidity of the asphalt.
(6) Modified asphalt: Modern highways and roads have undergone many changes: traffic flow and driving frequency have increased sharply, the axle load of freight trucks has continued to increase, and lane-dividing and one-way driving are generally implemented, requiring further improvement. The road surface has anti-flow properties, that is, the ability to resist rutting at high temperatures; improve flexibility and elasticity, that is, the ability to resist cracking at low temperatures; improve wear resistance and extend service life.
Modern buildings generally use long-span prestressed roof panels, which require roof waterproofing materials to adapt to large displacements, be more resistant to harsh high and low temperature climate conditions, have better durability, have self-adhesiveness, facilitate construction, and reduce maintenance workload. These changes in the use environment pose severe challenges to the performance of petroleum asphalt. Modification of petroleum asphalt to adapt to the above-mentioned harsh usage requirements has attracted people's attention. After decades of research and development, a wide variety of modified road asphalt, waterproof membranes and coatings have emerged, showing certain practical engineering effects. However, given that the price of modified asphalt is usually 2 to 7 times higher than that of ordinary petroleum asphalt, users have not yet fully grasped the engineering performance of the material, and the output of modified asphalt has grown slowly. At present, modified road asphalt is mainly used for paving applications in special occasions such as airport runways, waterproof bridge decks, parking lots, sports fields, heavy traffic pavements, intersections and road turns. Recently, modified asphalt has been applied to the maintenance and reinforcement of road networks in Europe, which has greatly promoted the widespread application of modified road asphalt. Modified asphalt waterproofing membranes and coatings are mainly used in waterproofing projects for high-end buildings. With the advancement of science and technology and the development of economic construction, the variety development and production technology of modified asphalt will be further promoted. The variety and preparation technology of modified asphalt depend on the type and amount of modifier and the composition and properties of the base asphalt (i.e. raw asphalt). Due to the wide variety of modifiers with different forms, in order to form a uniform material with petroleum asphalt that can be used for engineering applications, various types of modifiers have been evaluated over the years and corresponding formulas and preparation methods have been developed. However, most The modified asphalt that has been put into practical use is a patented technology and patented product.
4. Main uses
The main uses are as infrastructure materials, raw materials and fuels. Applications include transportation (roads, railways, aviation, etc.), construction, agriculture, water conservancy Engineering, industry (extractive industries, manufacturing), civil and other sectors.
5. Packaging and storage
Asphalt may need to be stored in storage tanks during production and use. If handled properly, asphalt can be heated repeatedly to maintain it at a higher temperature. quite a long time without its performance being seriously compromised. However, if it is exposed to oxygen, light and overheating, it will cause the hardening of asphalt. The most obvious signs are that the softening point of asphalt rises, the penetration decreases, and the ductility becomes worse, resulting in the loss of asphalt performance.