Road Maintenance

Asphalt Renewal

Wagga Wagga City Council looks after 2,288km of road and keeping them in good condition requires a variety of approaches to road works. In some high traffic areas renewing the top layers with asphalt, or hot mix, can be the best option.

This involves stripping back and disposing of the top layers of the road and replacing it with steaming hot asphalt, which is laid at around 170°C. The result is a smooth surface that can withstand high traffic volumes.

Asphalt renewal in Wagga Wagga

• To remove the old material quickly and efficiently, a Wirtgen Profiler is used:
  • Features a large spinning drum with 162 hardened steel teeth to break up and mulch the existing road surface.
  • This machine is capable of removing 0.3m of material in depth at a width of 2m in a single pass.
  • Travels at about 5km/h and weighs over 28 tonnes.
  • Powered by a 500kw Cummins diesel.
• Upon the site being prepared, new Asphalt is dispatched from the contractors plant in Bomen (locally made material).
• Asphalt is dispatched from the plant at approximately 170°C. The temperature ensures the bitumen / binder in the asphalt is pliable which allows rollers to get good compaction.
• Asphalt has a compacted density of 2.4 tonnes per m3.
• Each delivery truck can carry approximately 10m3 of asphalt per load, this equates to around 22 tonnes each trip

Road Rehabilitation

Rehabilitation works is the most comprehensive type of road project that Council undertakes.

It involves ripping up the bitumen seal, removing the top layer (pavement) of the road base and then stabilising the subgrade below that. The pavement is then filled with new material and sealed with bitumen and stone.

Depending on how long the stretch of road, its location, daily traffic volumes local access requirements such as shops, and weather conditions this type of work can take weeks or even months to complete, with access restricted to local residents only.

How it plays out

• Analysis of the condition of the road, its priority in the overall network and the primary cause of the road failure.
• Investigation of underground services, which can result in the need to lower watermains, electricity, stormwater pipes, sewer pipes and communication conduits or wires before road work begins.
• Profiling: removal of the seal and road base to 300mm deep.
• Stabilisation/protection of underground services that can’t be lowered such as gas mains and Telstra lines.
• Stabilisation of the subgrade to a depth of 300mm by mixing in a lime based product, this makes the foundation stronger and more water resistant.
• Replacement of the pavement to a depth of 300mm with new material.
• Pavement tested to ensure it meets compaction and moisture guidelines.
• Two-coat spray seal (a 14mm stone and a 7mm stone) to complete

Multitasking

The closure of a road for this kind of project also provides the opportunity for staff to complete other works such as kerb and gutter replacement, footpath repair, stormwater maintenance and sewer maintenance. Where possible these works are combined to maximise efficiency and minimise the inconvenience to road users and residents.

Why does it take so long?

While it takes little time to dig the up old road, the stabilisation of the subgrade can take time to complete. The mixing process involves a specialist machine that can mix to a depth of 450mm and complete 4000m² in a single pass in one day. The subgrade then needs to be compacted to design specifications, shaped to match road crossfalls and tested to ensure compaction and moisture specifications have been met.

For a section of road 500m long more than 1,500 cubic metres of road pavement is replaced, that’s a lot of truck movements! Each truck carries 10m³ or 20m³ if it has a trailer.

Care also needs to be taken when stabilising around services such as gas mains and Telstra lines to protect them. Unfortunately, due to the nature of the old plans it’s not uncommon to stumble across an underground service that is either in the wrong place or no-one actually knows is in existence. Staff also spend a couple of hours each day reinstating driveways to ensure residents can safely access their properties without supervision each night.

How long will the new road last?

Providing the road is resealed every decade or so, the road should not need the same level of attention for 30 to 50 years.

Why don’t you finish the road with asphalt/hotmix?

While asphalt is a quality product and relatively quicker to replace it is very expensive. For this reason it is only used in areas that receive very high volumes of traffic. When a road is rehabilitated as described in this fact sheet, a two coat seal provides the same level of longevity. While a two coat seal can result in loose stones to start, it only takes a few days to settle into a smooth surface.

Why can’t you do the work at night?

Where possible rehabilitation works is completed at night to minimise disruption to shops businesses and motorists. However it is considerably more expensive to complete night works, is disruptive for residents in high density areas and allowing traffic movements through the day can increase the amount of time it will take to complete a project. All of these factors are taken into account when deciding whether to complete day or night works.

Resealing

Wagga Wagga City Council undertakes a reseal program throughout the warmer months each year.

Resealing is a common preventative road maintenance technique where a new coat of bitumen and stone/aggregate is applied over an existing surface.

Council's annual reseal program extends the life of local roads by:

• Increasing the surface texture for better tyre friction
• Sealing cracks in the existing surface to protect the pavement beneath from moisture
• Preventing the existing surface from further oxidisation (UV degradation)
• Maintains the surface to a good condition

In preparation for the reseal, stage maintenance works will be carried out on streets. This preparation work ensures the best surface is available for the reseal.

There will be changed traffic conditions during the works and motorists should also be aware of loose stones while the surface interlocks, which takes two to three weeks. A street sweeper will return to all resealing sites after this period to remove any remaining loose stone.

Parking is unavailable during the reseal process, although roads can often be open to local traffic needing to access driveways. To assist Council with undertaking reseal works, it is recommended residents make alternative parking arrangements and park off the designated street.

Why don’t you fix potholes instead?

A common concern from residents about the resealing program is that the roads on the list do not need fixing and that the money could be better spent elsewhere.

While there are a number of roads around the local government area that have been identified for rehabilitation this is a much more costly and time consuming process.

The resealing program is a preventative maintenance technique utilised to maintain the useful service life of road infrastructure. It is very effective in reducing ongoing maintenance and ensuring longevity of the surface.

Without preventative maintenance like resealing, the life of the road is greatly reduced and it’s more likely to develop potholes and other defects.

Why is the road bumpier after a reseal?

A reseal involves the application of new aggregate to the road surface. This results in some loose material being present on the surface for a period of a few weeks while the surface settles and the aggregate achieves embedment. A street sweeper will return to the reseal sites after this period to remove any remaining loose stone.

Motorists are asked to take care following new reseal work due to the changed traffic conditions.