Asphalt

Asphalt, also known as bitumen (UK English: /ˈbɪtjʊmɪn/, US English: /bɪˈtjuːmən, baɪ-/), is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product; it is a substance classed as a pitch. The primary use of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including the production of roofing felt and for sealing flat roofs.

History

The history of asphalt is long and significant, dating back to its use in the ancient world. The earliest references to its use were by the Sumerians around 3,000 BC, where it was used in the construction of walls and towers. The material was also known to the ancient Egyptians, who used it in the mummification process.

Production

Asphalt is produced through the distillation of crude oil during petroleum refining. The process involves the removal of lighter fractions like liquid petroleum gas, petrol, and diesel, leaving behind a heavier product that is further processed into asphalt. There are two main types of asphalt production: penetration grading and viscosity grading, each of which categorizes asphalt based on its physical properties.

Composition

Asphalt is composed mainly of alkanes, cycloalkanes, and various aromatic hydrocarbons. It is waterproof, adhesive, and highly viscous, properties that make it an excellent binder in road constructions. However, the exact composition of asphalt can vary depending on the crude oil source and the refining process.

Uses

The most common use of asphalt is in road construction, where it serves as the binder in asphalt concrete. It is also used in the manufacture of roofing materials, where its waterproofing properties are invaluable. Other uses include sealing and insulating purposes in various types of buildings and structures.

Environmental Impact

The production and use of asphalt have environmental implications. During production, greenhouse gases are emitted, contributing to climate change. Additionally, when asphalt is heated, it can release harmful volatile organic compounds (VOCs) into the atmosphere. However, recycling asphalt can mitigate some of these environmental impacts, as it reduces the need for new raw materials and the associated energy consumption and emissions.

Recycling

Asphalt is highly recyclable, and its recycling is a critical aspect of modern road construction. Recycled asphalt pavement (RAP) can be reused in new asphalt mixtures, significantly reducing the need for virgin materials. This not only conserves natural resources but also reduces the carbon footprint associated with asphalt production and use.

Health and Safety

Working with hot asphalt can pose health and safety risks, including burns and exposure to toxic fumes. Proper safety measures, such as wearing protective clothing and ensuring adequate ventilation, are essential to mitigate these risks.

See Also

• Pavement (material)
• Bituminous coal
• Petroleum
• Road surface