Bitumen
- Definition: Bitumen is a viscous, black, sticky substance that is a byproduct of the distillation of crude oil. It is also found in natural deposits, such as tar pits.
- Function: Bitumen acts as a binder or glue in paving materials. It holds the aggregate (crushed stone, sand, etc.) together in road construction and other applications.
- Usage: Bitumen is used in a variety of applications, including roofing, waterproofing, and as a binder in asphalt concrete.
Asphalt
- Definition: Asphalt is a mixture of bitumen and aggregates (like sand, gravel, and crushed stone). The bitumen binds the aggregate particles together to create a cohesive, durable surface.
- Function: Asphalt is used primarily for constructing roads, driveways, parking lots, and other paved surfaces. It’s the final product that we see on roads and pavements.
- Types: Asphalt can vary in composition depending on the type of project. For example, there are hot mix asphalt, warm mix asphalt, and cold mix asphalt, each suited to different conditions and uses.
Summary
- Bitumen: The binding agent, a raw material.
- Asphalt: The final paving material, a mixture of bitumen and aggregates.
In simpler terms, bitumen is a key ingredient in asphalt, but asphalt is the actual material used for paving roads and driveways.
What is asphalt made of?
Asphalt is a blend of graded aggregate, sand, filler (generally flyash) and liquid bitumen. The materials are heated and mixed with hot bitumen which binds the materials together. The hot mixed asphalt (160 – 180 degrees C) must be laid and compacted before cooling. The surface texture is smooth and uniform, (although some asphalt designs are open-graded and course textured to reduce water spray and noise on highways). The compacted layer thickness for drives and residential streets is 25 – 40mm, increasing to 50mm + for main roads and highways.
What is Bitumen?
Bitumen is also used for spray seals. Liquid bitumen is sprayed onto a prepared surface. There are different types of bitumen which can be sprayed hot or cold. Most spray seals are a two coat system. After spraying the first coat, a single sized aggregate is evenly spread then rolled. A second coat of bitumen is sprayed, then covered with a smaller sized aggregate and rolled again. The result is a rough textured finish with an amount of excess (or loose) stone on the surface which can be left or swept off after a period of time. For driveways a 10mm & 5mm aggregate is used, for roads and highways a 14mm & 7mm combination and greater is used.
