I have seen several articles about pavement melting in the UK and Australia due to high temperatures. The linked articlesays that this happened because UK temps hit 33 C, or 91 F. In the US, that’s considered springtime in much of the country! Seriously, temps in the 90’s to 100’s are pretty common here, yet the asphalt doesn’t melt. Is the blacktop formulation that much different across the pond(s)?
Apparently, yes: Who, what, why: When does tarmac melt? - BBC News
Unless you go for high cost additives, making it more heat resistant makes it more brittle in cold weather.
Not that asphalt doesn’t melt in the US as well:
As you’ve already found, there are many different recipes for the binder that holds asphalt together. You design the asphalt mix using the type of binder that will work best under the traffic conditions and the weather that you expect the road to experience in the future. If your estimate about either the traffic volume and weight or the weather are wrong, the asphalt will not perform properly. In this case, it’s “melting”. I use the quotation marks because I doubt that it’s becoming liquid, it’s just losing strength and deforming under the weight of the trucks.
If the road had been designed here, and designed properly, it would have used a mix that could handle 120F plus weather, because we regularly have multiple days every year over 100F and multiple days over 110F aren’t unusual. What our asphalt wouldn’t react well to would be sustained temperatures below freezing. It wouldn’t fail quite as spectacularly as “melting”, but it would become prone to cracking, which would result in alligatoring and potholes.
If the tarmac is a problem here, they usually send out the gritters to spread sand on top of it. The problems are usually found on rural roads; motorways are not affected.
“Asphalt” doesn’t melt because “asphalt” contains rocks. But the asphalt component of “asphalt” certainly does get soft enough to flow, if you have a soft asphalt.
Fortunately, it’s normally spread out flat on a playground, so when it melts it doesn’t flow anywhere. It just sticks to your shoes.
In America, melting asphalt is unacceptable.
Pot holes, on the other hand, …
Not across the ponds per se, but depending on location. 33ºC would send Sweden into a total collapse (AC? What’s that?); in Spain there’s areas which get those temperatures in February. Their formulations are intended to survive winters; ours to survive summers. I saw the tar in one of my home town’s largest streets melt once, but temps were officially 48ºC in the shadow and that spot got day-long sunshine.
- extraofficially, that was the thermometer’s limit and the metereologist eyeballed it as an actual 50ºC
Thanks, all! I figured the formulation was the answer, but wasn’t sure why. Now I know (won’t my children be proud? Dad knows another piece of useless information)!