Resurfacing treatments

In Canberra there are a number of road resurfacing treatments used. There are several key aims of resurfacing works:

• to waterproof the road, prevent moisture entering the road base and stop the formation of potholes
• to improve the skid resistance of the road surface
• to fill cracks in the pavement

Resurfacing does not generally make much difference to the ride quality as the surfacing is generally thin. Patching works ahead of resurfacing works target ride quality improvements.

Pavement Preparation

Prior to the resurfacing, some work is required to prepare the surface for resurfacing. These treatments are designed to remove some of the existing defects which will result in an extended pavement life and include:

• Patching to remove pavement failures, surface defects and for shape correction. Prior to patching the pavement will be marked for repair.
• Crack sealing to fill some major cracks and to waterproof the pavement.
• Concrete kerb repairs to ensure water continues to drain into the stormwater stumps along the street.
• Tree trimming to remove low overhead branches which may damage resurfacing equipment or waste removal vehicles.
• Street sweeping to remove any debris on the surface of the road which may prevent adhesion of the resurfacing products.

Resurfacing

The resurfacing works will generally be undertaken between October and April each year when the weather conditions are more conducive to the success of the resurfacing treatment. Cold and wet roads increase the risk of resurfacing failures. In Canberra there are a number of road resurfacing treatments used.

The resurfacing treatments used are:

1. Rejuvenation

   These treatments are a petroleum based product that are often sprayed cold onto the pavement to protect it from oxidation and to extend pavement life. These treatments are designed to extend the binder life of the original wearing course.

   These treatments rely on the strength of the existing pavement and extend the wearing course by five to ten years.

   These treatments may be covered with fine sand to soak up an excess product and to accelerate the drying process which may take one to two hours.



2. Reseal

   This process applies a bituminous liquid evenly over the road surface and this is covered with aggregate which is rolled to achieve better adhesion between the binder and aggregate. This process can use hot sprayed bitumen or a cold sprayed bituminous emulsion.

   This process allows for the inclusion of rubber to span cracks in the pavement and petroleum products to delay the curing process.

   Multiple applications of bitumen and aggregate can be applied to increase the surface life, provide a smoother surface and reduce the noise generated from a road.

   A fabric can be added to the process to assist in the spanning of cracks and to strengthen the pavement.

   The life of the surface treatment will vary depending on the thickness of the binder and the traffic using the road. Arterial roads which carry high traffic volumes may only achieve a five to 15 year life while low speed and low volume streets like cul de sacs may achieve a life of 25 years.



3. Microsurfacing

   This is a cold mix of bituminous emulsion and aggregate which is manufactured on site and applied in a thin layer. The material is levelled by a screed which is dragged over the surface by the paving machine.

   This product relies on the strength of the original pavement and will reflect cracks in the pavement.

   The curing of this product relies on the separation of the water from the bitumen in the emulsion and it can take one to three hours for the material to cure enough to traffic.

   The finished product has a smooth surface and is often mistaken for asphalt.



4. Asphalt

   This hot applied mix of bitumen and aggregate is manufactured at a plant located in an industrial area and transported to site by a tip truck. The hot material is tipped into a paver which places a uniform layer of the product on the road and is compacted while still hot.

   This is a product which has the ability to resist significant turning movements and provides significant additional strength to the pavement. This product is ideal for placing on intersections, roundabouts and in smaller patches.

   The material can be trafficked as soon as it has been compacted if required.

   There are a number of variants to this process which can produce greater surface strength, the drainage of water or the resistance to cracking. This treatment produces a finished surface which is smooth and generates low traffic noise.

   The service life of the product depends on the depth of asphalt laid, the strength of the base and the amount of traffic that use the road. In general the service life of a highly trafficked roads is over ten years while residential streets often deliver 25 to 30 years of service.



5. Thin Open Graded Asphalt Surfacing (TOGAS)

   This is a thin asphalt surfacing with reduced strength characteristic than asphalt while having low noise emissions. This product is often used on surfaces which have excess bitumen or poor skid resistance.

   This product has a service life of about 15 years.



6. Cape Seal

   This is a reseal which has a layer of microsurfacing placed over the top to provide significantly lower noise emissions. This treatment looks like asphalt and has a service life greater or equal to a reseal.

Comparative Cost and Life of Treatments

Note that these cost figures are indicative comparisons between the treatments and the expected life that should be gained from the treatments on Municipal streets and Arterial roads. The price range will vary according to the number of coats of product laid and the depth of product.