It’s been a busy few weeks for Thermal Road Repairs as our crews have been out gritting the streets of Manchester. This is our first winter working for Manchester City Council, having won a six-year contract to provide winter services last year.
Gritting – spreading rock salt over road surfaces – is important work, because it helps to keep motorists safe when the temperature drops, and allows traffic to keep flowing, which is vital for the economy of a big city like Manchester. It works because salt lowers the freezing point of water, preventing ice from forming.
Ice isn’t just bad news for the safety and journey times of road users. It can also accelerate the rate at which roads deteriorate. It is particularly bad news for roads that have been less well maintained: those that already have cracks which the water can seep into.
When water freezes into ice, it increases in volume by about 9%. So, if the water is sitting inside a little crack in the asphalt that forms the road surface, it will expand and increase the size of that crack just a little bit. Wider cracks, with the action of ice, and the pounding of traffic may form into potholes which will then worsen as time goes on.
Certainly, in the more Northern regions of the UK, the temperature has been cycling around zero - dropping below in the night, rising above during the day – over the past few weeks. That can mean that ice forms in a crack, then melts, water fills the slightly widened crack, freezes and then widens it further, a phenomenon known as freeze-thaw.
For country roads, that may not have as many layers as suburban roads, cold weather may cause more issues. Water can collect in the soil beneath the asphalt, freeze, and in some cases causing cracks from the bottom up.
Another potential issue when temperatures fall is that the property of the road surfacing material changes. When the bitumen in an asphalt mix gets colder, it tends to get more brittle, making it more susceptible to cracking. It is possible to produce asphalt mixes that can cope with a wider range of temperatures, but that’s no help for roads that were laid some time ago.
So, what can be done, aside from gritting when the cold weather is coming? Where funds allow, the most important thing is to seal up any cracks, no matter how tiny. Applying road surface treatments such as slurry seal or surface dressing means that the water won’t be able to get into those tiny cracks.
And, in an ideal world, potholes should be treated as soon as they form. Freeze-thaw increases the size of potholes that have already formed, as well as hastening the formation of new ones.
Of course, we would advocate for using a permanent repair process, like Thermal Road Repairs’ system, for those potholes. By heating up the asphalt in and around a pothole, adding a small amount of new hot asphalt, and compressing it all together by rolling it, a joint-free repair is created. And that means that there are no tiny cracks around the edge of the repair – and hence, nowhere for water to get in, freeze and do its damage.
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Thermal Road Repairs: Decarbonising the asphalt repair industry
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