New and innovative materials are helping to speed up pothole repairs and to make repairs last longer even as persistent wet weather across eastern Australia makes it difficult to fill the holes using typical material mixes.

As thousands of potholes have sprung up amid ongoing wet weather for much of the year, the New South Wales Government is trialling of a range of ‘cold mix’ materials to determine which can be used to fill the holes without crews needing to wait until roads dry out.

Minister for Regional Transport and Roads Sam Farraway said the trials aim to determine which materials are most effective during severe weather.

“We’ve asked the experts for solutions and new technology we can foster to patch up potholes faster when it’s cold and wet,” Farraway said.

Across much of eastern Australia, potholes have sprung up on roads in their hundreds of thousands this year on account of the large volume of persistent rain which has fallen since the first wave of severe weather hit in February.

In New South Wales, the state has needed to fill more than 152,000 potholes on state roads since the beginning of March – more than four times the number compared with last year (local councils are responsible for pothole repair on local roads).

The includes more than 18,500 potholes in Sydney alone – the equivalent of re-sheeting the Sydney Cricket Ground 35 times.

Potholes often occur when road pavements become saturated following rain.

As vehicles roll over it, the water in the pavement is compressed under the weight of traffic. This compressed water pops out any weak points in the asphalt and thus forms potholes.

This can be further exacerbated where the road already has cracks in it and vehicle tyres force the water deep into small cracks and crevices.

Over time, this pressure breaks off small bits of the asphalt.

A small pothole can quickly get wider and deeper as more traffic goes over it.

Consequences are serious.

For vehicles which drive over them, potholes can cause damage ranging from punctures to broken rims to problems with suspension and alignment.

For motorbikes, potholes can cause the rider to lose control and suffer serious injury or fatality.

Typically, potholes are filled via ‘hot-mix’ asphalt, which delivers a strong and durable repair.

However, using this type of product during wet weather is difficult as the material can only be applied when the road is dry.

By contrast, traditional cold-mix products are not as durable or strong. Their use is mainly short-term temporary repairs or to cover up minor cracks.

However, the government has been trialling a range of innovative cold-mix materials to see which can be used in wet weather whilst also delivering a strong and lasting repair.

One example is a cold mix product that uses water to ensure that it sets properly on site.

Whilst the product could be used in dry weather with the addition of water, it is ideal for use in wet weather as it soaks up rain which helps the pothole material set.

Thus far, crews have not needed to refill any potholes which have been filled using the product.

The material being used here is a cold mix material but uses the water to set properly and so is ideal for application in wet weather. (image provided by NSW Government)

Mathew Wilson, Executive Director of Road Maintenance and Motorway Partnerships at Transport for NSW, said TFN has been working with industry partners to find innovative materials and new pothole filling methods which can be applied in wet weather yet still deliver a durable result.

Wilson said a number of products from around the world will be trialled during November.

“It’s been a terrible year for potholes,” Wilson said.

“Wet weather is the bane of our lives when it comes to pavements. It unfortunately creates potholes and makes them very difficult to fill as well.

“We have been working with industry to try to find new materials and new ways that we can fill the potholes to make the ride safer for the travelling public.

“We have a number of products from across the world that are going to be trialled on Sydney’s roads to see how they work in wet weather and how we can better fill potholes in the rain.”

Wilson said challenges caused by ongoing rain should not be underestimated.

“I’ve been working road maintenance for nearly 20 years. This is the worst I have had to deal with in terms of wet weather in my entire career,” he said.

“Even working abroad, I have never seen as much rain as this in short periods.

“It makes filling potholes really challenging. With the amount of rain we are getting, they form really quickly.

“And with the amount of traffic we have in Sydney, that just makes it worse. We have a perfect recipe for many, many potholes forming.

“But we are working 24 hours per day, running around the network and filling them as quickly as we can.”

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