A road is built in layers: the base or formation, the pavement, and on top the seal. The seal is the layer you drive on, and its job is to protect the more expensive layers underneath by taking the wear and keeping water out. When it breaks down, you reseal it rather than rebuild the road. There are several types of seal, and the right one depends on the traffic, the climate and the budget. Here is a plain glossary.
Hot bitumen seals
The most common spray seal on bitumen road surfaces. Bitumen comes in different grades, from hard and brittle to soft and fluid, and it has to be liquefied before it can be sprayed. It is heated and, with a cutter added to reduce its thickness, sprayed onto the surface where it soaks in and grips both the road and the aggregate spread on top.
Emulsion seals
An emulsion is bitumen dispersed as tiny droplets in water, which lets it be applied at lower temperatures than a hot seal. It works much like a standard spray seal and is a good way to extend the life of an existing road by restoring the surface, grip and waterproofing. Adding polymers gives a polymer-modified emulsion with excellent elastic and adhesive properties for a stronger bond.
Dust seals
An intermittent seal applied to the surface of dirt and gravel roads to keep the dust down. It is a low-cost, practical option for locations where a full engineered road is not economically justified, and it gives an unsealed road a usable sealed surface.
Hot mix asphalt
A mixture of aggregate, sand and filler heated and combined with hot bitumen, then laid at a set thickness. The aggregate size is matched to the job: larger stone for roads, smaller for driveways, car parks and sports courts. It gives a smoother, more durable finish than a sprayed seal.
Primerseal
A first-stage seal sprayed onto a prepared, non-primed surface and covered with aggregate. It is not meant to be a long-term wearing surface, and is usually covered by a final seal or an asphalt overlay one to three years later. It holds the surface and lets controlled traffic on almost straight away.
Spray seals
Also called sprayed seals, chip seals or bitumen seals. A waterproof binder is sprayed onto the surface, then covered with a thin layer of aggregate that is rolled in. Polymer or crumb rubber can be added to the binder for extra strength and flexibility. Spray seals can be single or multiple layers.
Two-coat seals
A layer of bitumen with larger aggregate, sealed over with a second layer of bitumen and smaller aggregate. The mix of large and small stone makes it more hard-wearing than a standard spray seal, and particularly resistant to stripping where traffic turns, which is why it suits intersections and driveways.
Choosing the right one
Every surface is different, and the best seal depends on the condition, traffic, climate and how long you need it to last. That is the call we help clients make across Brisbane, the Gold Coast, Ipswich, the Sunshine Coast and Toowoomba.
For more on the seals we lay, see our spray seal and 2 coat seal pages, then get in touch and we will recommend the right treatment and give you a written quote at no cost.