Open Graded Asphalt Surfacing

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Our team at Tidey & Webb have helped transformed many properties with a residential surfacing or commercial surfacing project over the years and we pride ourselves on being the Sussex surfacing specialists that enhance your premises with a new, durable and high-quality surface.

One surface type often required by commercial properties and local authorities is open-graded asphalt. Selected for use on road surfaces that may be prone to wet weather, open-graded asphalt is a porous asphalt mix formulated to provide large voids that allow surface water to drain away and present a safer surface type for road users.

What is Open-Graded Asphalt?

If a new surfacing project such as a new road, race track or carpark is on the cards, you will likely be looking for a surface that provides durability, affordability and longevity, choosing an open-graded asphalt surface could be your best option. Open graded aspalt is a porous mix, that provides excellent drainage allowing the surface to be free from excess water. With safety in mind, open-graded asphalt gives road users added confidence whilst driving. You may also see them refered to as an open graded friction course or OGFC.

Benefits of open-graded asphalt

Open-graded asphalt is a premium surface type to choose for road surfaces. It is often referred to as a popcorn mix and is used to help promote road safety. With the voids that this surface type provides between the angular surfaces of the aggregate, you get rapid drainage from any surface water or rain. As a result of this, you get a huge reduction in tyre spray, improved visibility of road markings and reduced glare from headlights when driving at night and the surface is wet. Furthermore, thanks to the reduction of standing water, skid resistance is also maximized.

The benefits are not just safety based though. Opting for an open-graded road surface also delivers a cost-effective surface type. Using thin layers to construct the surface results in fewer materials being used and wasted and as a result, less cost. Finally, traffic can drive up decibel levels, but when you use open-graded asphalt you can see a marked reduction in the noise. In some cases when compared to dense graded asphalt the difference can be as much as 3dB.

Uses of open-graded asphalt

Open-graded asphalt is a versatile and cost-effective surface type that is regularly used by councils and businesses for the construction of the following surface types:

  • Car parks
  • Council-maintained roads
  • State-maintained roads
  • Sports facilities
  • Commercial properties

With its low noise properties, the demand for open-graded asphalt surfacing has increased considerably over recent years and with its lower cost it has become an option that many have started to consider as a viable surfacing option.

What is the difference between open-graded asphalt and dense-graded asphalt?

Whilst the names may be fairly similar, the composition is significantly different. Dense grade asphalt, when constructed correctly is more or less impermeable. It is often used for pavements as well as roads. Constructed of a well-graded aggregate and asphalt binders that are either with or without modifiers, the dense graded asphalt works well for structural, friction, levelling, and patching needs.

Open-graded asphalt though is designed with permeability in mind. It uses crushed stone, or gravel and just a small amount of sand. Where dense graded asphalt has its particles tightly bound together, open graded contains fewer of them, allowing for large air voids between both the course and medium particles. These voids can make up as much as 20% of the total volume and allow for the surface to become more permeable.

Asphalt or tarmac?

Should you be looking for a new surfacing option, the choices are quite wide-ranging, but much depends on what your surface has to handle. Is there a high level of traffic? Does the surface suffer from intense levels of heat or increased rainfall? What is the ground underneath the surface like? All are valid questions and the team at Tidey & Webb can help you navigate your way through them to find the best solution.

Frequently compared are asphalt and tarmac. Each provides varied benefits but an open-graded asphalt could be your best option. Why? Let’s explain.

Asphalt provides much higher levels of strength and durability than tarmac giving it a prime position as a choice for motorways, car parks, cycle paths and more. Whilst tarmac driveways are great for their purpose, they can be more susceptible to damage from petrol and fuel. With regular preventative maintenance, you can keep your tarmac surface in fantastic condition easily.

As mentioned earlier, an open-graded asphalt surface is permeable, which is vastly beneficial to roads, especially in areas where rainfall and high levels of traffic are likely to meet. Tarmac on the other hand does not offer quite the same quality and is more or less impermeable.

Asphalt is also fully recyclable, allowing for the materials to be reprocessed into a new road surface elsewhere should it be needed. Tarmac on the other hand is recyclable as an unbound aggregate.

Cost-wise, asphalt does tend to also cost less than tarmac when being used for small surfaces, for larger areas the costs can rise a little higher than those accumulated by laying a tarmac surface. Our team will be able to give you a full quote, for free so that you can compare prices, properties and advantages before making a decision.

Other asphalts to consider

Should an open-graded asphalt not be necessary for your needs, the team at Tidey & Webb can help with many other asphalt types that offer similar benefits for a wide range of purposes.

Polymer modified asphalt is an affordable option for roads, pavements, and playgrounds.

Coloured asphalt is a popular choice among those looking for a new driveway, playground or other type of surface that could benefit from a little vibrancy or that needs to make a safety statement.

Maintenance of open-graded asphalt

Open-graded asphalt is used for high traffic areas and should provide longevity as a road or other surface type. That isn’t to say that problems may not occasionaly arise. Preventative maintencance can stop these problems from either starting or developing further.

If your surface begins to exhibit low levels of damage, such as a crack or a small pothole, it can be sealed using a dense grade mix. Should the damage appear a little more severe and potentially cause accidents on the road, these should be filled with open graded material. This is because opting for the denser material you would have used on smaller holes will actually act as a barrier and block the water flow leading to potentially larger problems.

If there are severe signs of damage such as raveling, you may need the top layer to be replaced, simply overlaying them is not the best way to get the optimum performance from your open graded asphalt surface.

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