With temperatures plummeting in Scotland and northern England, and snow falling as far south as Norfolk, our potholed roads are in for a beating. Below-zero temperatures serve to speed up the deterioration of roads, as water in cracks and trapped beneath asphalt course freezes and expands.
The weather warning comes in the same week that the AA warned motorists and cyclists to avoid puddles where safe to do so because they could be hiding potholes. The AA reports that its patrols have attended 52,541 pothole-related breakdowns in October this year, 12% more than last year, and a record total for the month of October. The average for the year so far is 1,500 such callouts every day.
Winter weather is bad news for roads, especially those that already have cracks and potholes in them. And unfortunately, as the recent spate of storms illustrates, precipitation events are getting more concentrated thanks to climate change.
If there are cracks in a road water can run into the cracks. Vehicles driving over the cracks force more water into them at pressure, causing small pieces of material to break off, speeding up the rate at which the crack widens. Over time, many cracks grow into potholes. And when it’s really cold, the expansion of water as it freezes – known as freeze-thaw – helps with that job.
Depending on the road structure, the cracks may carry water down to the soil beneath the layers of asphalt so that, in time, it washes away. Then the asphalt has nothing to support it and collapses into the dip in the soil. If water trapped below the road freezes, that can push the asphalt upwards, again leading to potholes, which often happens on country roads.
Potholes are worsened in wet weather or when there’s slushy snow too. Vehicles driving over them cause the water to wash out loose bits of material from the pothole, and its edges then cave in faster.
Unfortunately, snow, rain and freezing conditions are also bad news for potholes that have been filled. Most pothole repair methods leave a joint in the road, a tiny gap between the existing material and the new material. And that joint is a weak point – in effect a crack.
Clearly, some repairs are more susceptible to failure than others. For critical highways, it may be necessary to quickly apply material into the hole, compact and move on. Such repairs are not expected to have a long life. But even for a so-called permanent repair, where the failed material around a pothole has been carefully cut out and the edges treated with a sealant before hot asphalt is applied, the joint remains a weak point.
The solution is to find a way to remove that joint. Which is what Thermal Road Repairs’ technology does. By heating up the material in and around a pothole, adding hot asphalt and mixing new and old up before compaction, the joint is removed. This means that there are no little cracks to be widened by forces from the traffic and by water ingress.
Although the industry was delighted when the Chancellor allocated an additional £8.5bn to road maintenance, everybody realises that this must stretch a long way to tackle the backlog of road damage. The latest Annual Local Authority Road Maintenance (ALARM) report estimated the current cost of getting our local roads back up to scratch at £14bn. We can’t afford to waste precious funds by fixing the same potholes over and over again.
As Einstein purportedly said: “Insanity is doing the same thing over and over again and expecting different results”. But you don’t have to be Einstein to see that current pothole repair strategies aren’t working.
-------------------------------------------------------------------------------------------------------------------------
Thermal Road Repairs: Decarbonising the asphalt repair industry
-------------------------------------------------------------------------------------------------------------------------
Sources
https://www.asphaltuk.org/alarm-survey-page/