AYESHA RASCOE, HOST:
Extreme heat is not kind to infrastructure. This summer, interstate highways in Texas and Utah buckled, causing major traffic delays. Last summer, high temperatures twisted railroad tracks outside San Francisco and caused an airport runway in England to seem to melt. And we can expect more of the same as climate change brings higher temperatures around the globe. Here to explain why this is happening is professor Amit Bhasin at the University of Texas at Austin. Welcome to the program.
AMIT BHASIN: Thank you, Ayesha.
RASCOE: So I hear there are two different types of roadways - asphalt and concrete - and they each have their own problems. And I will admit - asphalt, concrete - I don't quite know the difference. And then don't start talking about cement. I don't know the difference. So let me (laughter) know. I'll be honest.
BHASIN: And that's perfectly fine. So most of the roads in the U.S. are asphalt pavements, but there are also several significant highways and roadways that are concrete pavements. So concrete is a very rigid material. You, of course, use it for construction of buildings and so forth. When the temperature goes up, it starts to expand. And because it expands, you need to accommodate that expansion somewhere in the pavement, right? So that is done either by providing joints or steel reinforcement and allowing very small cracks to occur and so forth. This is all part of the design. I mean, we design it to handle this range of temperature.
But now, if I have much more than what I designed a slab for - in a jointed concrete, if you don't have that space for the concrete to expand, what's it going to do? It's going to push against each other. It's going to start buckling up at the joints. It's going to start breaking apart. And asphalt pavements - when you're talking about high temperatures, the problem with asphalt is that it becomes softer than what it is designed to be. And when the traffic passes over it, those tires are going to rut into the pavement and create deformation and rutting and damage the pavement.
RASCOE: I've seen pictures of train tracks that are twisted kind of like spaghetti. Why does that happen?
BHASIN: So it's, again, the same thing, right? If you go back to your high school physics, you remember that when you heat materials, they expand. When you cool them, they contract. So steel also expands. And so what happens is if the temperature goes higher than what it was designed for, then imagine a thin rod, and you press it from both ends inwards. Then the rod was - it's suddenly going to bend and buckle along its length.
RASCOE: How hot do these surfaces have to get to start experiencing these sorts of issues?
BHASIN: Yeah. So in any design process, what we do is we take the local climatic condition, and we look at historical data. So you go back and look at 50, 100 years of data. Then you say, OK, these were my seven hottest days in the last 50 years, 100 years. These were my seven coldest days. And if I want to be able to handle these extreme temperatures in this particular location, I'm going to design this material and this structure to be able to handle that and maybe depending on the reliability and importance, maybe a little bit more than that. Now, history is no guarantee of the future - right? - as we're breaking all kinds of records here. So those designs that were intended to handle a certain range are now slowly hitting their limits.
RASCOE: There are places in the world that are really hot, you know, obviously, like Dubai, and they build all sorts of infrastructure. So what could be done to make infrastructure more heatproof?
BHASIN: Oh, absolutely. I mean, it's not that we don't have the tools or technology. Wisconsin designs are going to start looking like Texas. Texas designs are going to start looking like the Middle East. And the Middle East designs are going to push the envelope to have more and more engineered systems towards higher temperature if the temperature keeps going up. So it's not that we don't have the tools or solutions to design and solve these problems, but if we overdesign things, that also means excess cost. And these are all - most of the roadways are primarily taxpayer-funded infrastructure. So - and if we underdesign it, the system fails. And if it fails, we again pay to fix it, right? So we're - we have to guess within a very narrow margin what we expect the future to be and design it there.
RASCOE: But if temperatures keep rising, something will have to give, right?
BHASIN: Yes. And that's where - there's a lot of partnership between agencies and universities conducting a lot of research, looking at innovative materials, more environment-friendly materials, increasing the use of recycled materials and all of these techniques to combat this change in climatic conditions. This is one of the biggest problems that we have in our industry, and we're looking at it very closely.
RASCOE: That's Professor Amit Bhasin, director of the Center for Transportation Research at the University of Texas at Austin. Thank you so much for joining us.
BHASIN: Absolutely. It was a pleasure. Thank you, Ayesha. Transcript provided by NPR, Copyright NPR.
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