What is Asphalt?

Asphalt, a bitumen-bound mix, is laid hot and then allowed to cool and cure. Normally, it feels firm enough for light use within a couple of days. However, the binder continues to harden and gain strength over several months, which is why new asphalt is more vulnerable to scuffing and indentations early on.

Dense bitumen macadam doesnt come in one standard thickness – its made to suit the job. On most real-world projects, a layer is in the region of a few centimetres thick, with heavier-duty roads and yards needing a deeper build-up than light-use areas like small car parks or access roads. The exact thickness is set at the design stage.

This means the finished pavement can cope with the expected traffic and tie in properly with the layers beneath and the surface course above.

Bitumen is a thick, black, sticky material produced when crude oil is distilled. In paving, it serves as the binder that holds aggregates together in an asphalt mix. It is highly adhesive and waterproof, helping protect the roads structure from water damage and keeping the surface intact under traffic. It is used as a binder in both hot-mix and cold-mix asphalt, and it also appears in roofing and other waterproofing products.

Tarmac is where tar is mixed with macadam crushed stone before laying, then compacted with a roller. It was patented by Edgar Purnell Hooley in 1902 as a more durable, dust-free version of basic macadam roads. In Tarmac, the tar acts like glue, holding the stones together and helping keep water out, which provides additional waterproofing and adhesion compared to macadam.