Tarmac, Asphalt, Bitumen…they’re all road surfaces, but no, they’re not all synonymous!
In this blog, we explain what Asphalt is, and its primary uses.
What is Asphalt?
First off, the confusing bit. In America, ‘Asphalt’ refers to the substance known in the UK and Europe as Bitumen. This is a by-product of the petrochemical industry. This sticky substance called Bitumen is used to bind aggregate and minerals – and it is used in both Asphalt and Tarmac. So, US Asphalt is an ingredient in UK Asphalt!
But what actually is Asphalt? In the UK, it consists of basic ingredients – aggregates, binder (bitumen), and filler.
Asphalt is used for play and sports areas as well as for constructing roads.
About 95% of the mix is aggregates. Aggregates used in Asphalt include crushed rock, sand, slags, and gravel. The final 5% is the binder – usually Bitumen, the aforementioned black and viscous by-product of the fractional distillation of crude oil (leaving polycyclic hydrocarbons).
A typical Asphalt pavement relies on a foundation or formation level for structure and stability. This includes both unbound and bituminous-bound materials. This allows load distribution from the traffic on the pavement before it reaches the lower formation level.
There are different types of Asphalt, so the make-up of the two ingredients can vary. The different types are categorised by the process used to bind the aggregates and the Bitumen.
What is Asphalt used for?
When we think of Asphalt, the most common usage that springs to mind is of course road surfacing. But as well as being spread on roads ranging from motorways to country lanes, Asphalt can be used for car parks, private driveways, plane landing strips, sports and play areas, and even for waterproofing roofs and underground storage spaces.
What are the different types of Asphalt?
Unfortunately, it’s not as simple as “Asphalt”. There are five different types that are commonly used, by homeowners and contractors alike:
Hot Mix combines around 95% aggregate – stone, sand, or gravel – with a Bitumen binder. This is heated and poured onto the surface at 150-180°C. It is the most durable type of Asphalt and is used in the most high-traffic scenarios, such as on motorways and airport runways.
Warm Mix is mixed at lower temperatures – 20-40°C less than HMA – so also cools more slowly than Hot Mix Asphalt. Less energy is used to make it, and therefore fewer fumes are produced too (a reduction of around 25°C equates to approximately 75% fewer fume emissions). This provides better working conditions for the crew laying the road and is better for the environment. It also uses emulsions, waxes, and zeolites, making it easier to spread and pour. It does not provide the same durability as HMA, however, so is recommended for low-traffic areas, or patching.
Cold Mix is the most affordable Asphalt solution. It doesn’t require any heating of the aggregate at all and is used most frequently for jobs like filling potholes and pavement cracks. This is possible because CMA uses Bitumen emulsified in water. This then breaks, either during compaction or during mixing – which produces the coating of the aggregate. Whilst it cures, the water evaporates. For roads that only see light traffic, it’s a great option.
All Asphalt needs maintenance and care to maintain its durability and give you the best longevity from the product.
Less common uses of Asphalt
Away from road surfacing, Asphalt can also be used in a variety of other environments. Architects often use it as an ingredient for the construction of dams and reservoirs, for example, and also in playgrounds and parks. It can be an ideal solution for flood control and preventing soil erosion. Asphalt can also be used in automotive manufacture, where it can be employed to prevent rust as well as minimise road noise in the fenders and bonnets of cars.
How well does Asphalt last?
You will have encountered a crack in an Asphalt road, and it can certainly be jarring to drive over. So you know that the material is something that doesn’t last forever. Asphalt’s durability does vary a fair amount, depending on a number of variables such as temperature, the presence of moisture, the amount of traffic it undergoes, and even varying ingredient make-up (whether it’s HMA, WMA, or CMA).
Asphalt will begin to erode over time. Heavy traffic, as well as exposure to extremes of heat and cold, cause expansion and contraction of the material. The use of a Sealcoat can really boost the longevity of the surface, too – it’s pretty essential for proper maintenance. This acts as a coating, protecting from traffic wear and tear, motor oil, salting, water pooling, and chemical staining. It also helps the surface not to crack – and cracks can cause much more profound problems if water can seep more deeply into the surface. This could lead to wholesale Asphalt renewal.
How best to maintain Asphalt
If properly cared for, a well-maintained Asphalt driveway can last in good condition for decades! It’s worth knowing what elements can harm your surface, too. Oil, motor grease, fuel, salt, and transmission fluid are all substances that can break down the Asphalt, resulting in the disintegration of the surface. The quicker you act the less severe the impact, too, as these chemicals can penetrate and then spread beneath the surface, causing a much bigger job.
The main maintenance jobs required to keep your surface up to scratch will be crack filling and seal coating.
Inspect your Asphalt regularly for cracks, as even hairline cracks can cause a problem. Filling cracks before they expand will keep the job small and manageable. Cold liquid pour Asphalt crack fill can be used to fill cracks that are up to half an inch wide, whilst hot pour crack fill works on gaps of up to an inch.
Sealcoating will need to be undertaken every few years dependent on variables such as your usage, drainage, and temperatures. Proper Sealcoating prevents any loss of flexibility, as well as preventing crumbling, oxidation, and cracking. This tends to dry over a few hours.
Here at Hazel & Jefferies we are expert road dressing contractors. Get in touch today to discuss any road surfacing needs.