What is asphalt?
Asphalt is a bituminous mixture of bitumen (a petroleum product) and mineral aggregates such as sand, gravel, and crushed stone. It is widely used as a paving material for roads, driveways, and parking lots, as well as a waterproof roofing material in building construction.
Asphalt is one of the oldest construction materials in human history. Natural asphalt was already used as a sealant in ancient times. Today, asphalt is industrially produced by blending bitumen with carefully selected mineral fillers. The bitumen acts as a binder that holds the aggregate particles together and makes the mixture waterproof.
Application
In road construction, asphalt is the most commonly used surfacing material. It is laid while hot and then compacted with rollers. Various asphalt mixtures exist, each with specific performance characteristics:
- Dense asphalt concrete (AC) — the standard surface course for roads and cycle paths.
- Stone mastic asphalt (SMA) — a wear-resistant surface layer for heavily trafficked roads.
- Porous asphalt (PA) — an open-graded surface that drains rainwater quickly and reduces tyre noise.
In building construction, asphalt is frequently applied as roofing. Bituminous roofing membranes consist of a carrier (polyester or glass fleece) coated on both sides with bitumen. These sheets are torch-applied or adhered to the roof surface to form a watertight seal.
Additionally, asphalt is used for waterproofing basements, foundations, and underground car parks. In civil engineering, it is essential for dyke reinforcement and canal lining.
Related terms
- Bitumen
- Roofing membrane
- Paving
- Foundation
- Waterproofing
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