Heat wave buckles highways in Minneapolis

buckled concrete.jpg

Apparently, while I wasn't paying attention, Minneapolis plunged into a heat wave. (I suspect this says something about the temperature-control powers of my 1920s stucco house. That, and my husband's practice of opening the house and turning on fans over night, and then closing all the windows in the morning. ) We hit a new record high—97 degrees F—yesterday afternoon, and more of the same is expected today.

But here's the really fun part: The heat caused serious highway damage in 21 different spots around the Twin Cities yesterday. We're not talking about gaping chasms opening up or anything. But heat and humidity do make concrete expand. If there's no place for it to expand to—as in the middle of a highway—it can buckle along the weakest point. The result: Sudden, big potholes where potholes did not used to be. Also: Traffic jams.

Bear that expected bad traffic in mind today, if you're joining me for the Twin Cities edition of the 1st Annual International BoingBoing Meetup Day. On the plus side, it's not likely to rain on us, right? Maybe we'll go for a purifying dip in the waters of Creek Minnehaha.

Via Amy Nelson

Image: American Film, a Creative Commons Attribution Share-Alike (2.0) image from swanksalot's photostream. Not a highway in Minneapolis, but buckled concrete, nonetheless.



  1. Every now and then you hear of this going on up north. I’ve wondered, being from an area of Texas where it gets a lot hotter than 97, why do y’all’s highways buckles and ours don’t?

    1. I figure two things, or one of two things: we make our highways to specifications that assume there will be high heat because it’s Texas, and two this happens from time to time and just doesn’t make the news (just some construction on the highway).

      Now frost heaves would make the news here though.

    2. We must have tougher asphalt. :P

      More seriously, Texas is on a giant plate of limestone bedrock that probably gives a lot less easily. Up North they even have things called basements that keep cool during the day. Oh the luxury!

      Maggie, y’all are always welcome here. Austin ‘ll be hitting 102 Fahrenheit today. Here that, Canadians? That’s almost 39 degrees in logical temperature scales!

      *Says the wuss spending the day in an air conditioned office.*

      1. Yep, that is kinda what I was thinking – I am in DFW. My first thought was “97 is a heatwave? You poor babies!”

    3. I think the people who mentioned colder winters in the North are spot on. Different asphalts/concretes for different climates; Southern roads probably wouldn’t hold up all that well in seriously cold weather.

      That said, the main heat-related issue we have here is melting asphalt (literally) when temperatures exceed 100° F or so. Buckling concrete highways, maybe every 10 years or so…

      1. This is the President George Bush Turnpike, or State Highway 190, north of Dallas.

        Oh sweet irony.

        “The best laid schemes of mice and men
        Go often askew,
        And leave us nothing but grief and pain,
        For promised joy!”

        ~ Robert Burns

  2. Someone needs to get on here immediately to note that such buckling is just an anomaly, and has nothing to do, statistically, with global warming.

  3. You’ve explained the fact that the buckle happens because of heat, but not really the science behind the buckling. I grew up in the Twin Cities and heard about pavement buckling on occasion during the summer. I just assumed everywhere dealt with it. Then I moved away from Minneapolis to other places that are just as hot but don’t seem to have pavement buckle. What is magical about Minnesota (and sometimes Wisconsin) roads that makes them buckle?

    The only thing that I can come up with is that there needs to be a slightly different composition of asphalt for the roads to put up with the extra beating from snow plows and much greater swing in temperature than other places. Minneapolis’ swing of 150F (record low -42f, record high 108f) is much greater than Austin’s swing of 114F (record low -2f, record high 112f). Any civil engineers care to enlighten us?

    1. That’s a good point. It gets a lot colder there, maybe the extreme changes are what weakens the highway coupled with the type of ground?

      Now I’m really curious. My google-fu is weak though, bring on the engineers!

  4. I was this happen one day driving back to the twin cities from madison.

    The oncomming traffic lane buckled like a little mountain ridge caused by two plates pushing into each other.

    The net result on traffic seemed to be that several cars speeding along at 80mph suddenly hit a ramp in the middle of 94 East bound.

    I always assumed it was really rare and the cause was that road some times gets laid at much lower temperatures and has to have higher regidity to be able to withstand -40 temps in the winter.

    Also a lot of southern highways seem to be concrete. I assume becuase concrete is lighter and reflects heat.

    1. A lot of southern pavement is concrete, not asphalt, because they don’t need to worry about freezing temps, but they do need to worry about blistering heat.

      It isn’t that concrete can’t take the freeze-thaw cycles as well as asphalt (in some regards it does a better job) but that potholes are inevitable in northern climes and repairing concrete pavement is much more complicated (and costly) than repairing asphalt.

      1. There is a billboard in Minneapolis claiming that Concrete makes for less pot holes. That may be true.

        I think its also true that the black color of the road is a life saver in many winter months.

        I think the best solution is brick on surface streets. Which is much more dependable but again much more expensive to repair.

  5. I’m not sure if this accounts for the difference, but when I lived in the Twin Cities it seemed like a lot of the highways were actually made of cement. Now I live near Phoenix, where many of the highways are made of asphalt.

    I’m guessing that cement holds up to snow plows much better than asphalt does. And with its built-in flexibility, asphalt handles expansion from extreme heat better than cement.

    But that’s just a guess. Any civil engineers out there know what’s really happening?

    1. When I saw it, it was Asphalt (Blacktop, or Macadam as we called it in PA)

      I think this won’t happen unless you have a dark or black surface to super heat a long stretch of road until it expands enough to cause a break.

  6. Am I inferring this correctly- you didn’t notice a heatwave with daytime temps reaching 97 F, because you live in a 20s stucco house and run fans at night?

    I find this really incredible, unless have a lot of shade and perhaps benefit from local valley cooling.

    We have a 1930 stucco bungalow with no tree protection (all the old grown trees were hacked down by neighbors years ago) and have a whole house fan- yet, if the temps even flirt with the mid-eighties, it feels like we’re sitting on the blast vent of Hades itself. We’ve never been able to hold out long when the temps start rising in the spring.

    I envy your great fortune- or mystical ways with stucco and fans.

    1. It’s just a guess, but I think we’re getting the benefit of a couple big trees, decent insulation, and stucco thermal mass. It’s also helpful that my house seems to have been built (intentionally? accidentally?) in such a way as to limit sun exposure on summer afternoons. There aren’t any big beams of light spreading around in here (although we do capture sun exposure quite effectively in winter).

      I’ve lived here four years now and it’s always taken a while–several days of very high temperatures or weeks of just general warmth–for this house to heat up to the point that it becomes uncomfortable. And it’s been cooler than average in Minneapolis right up until last week. (In fact, the downside is that I was still wearing a sweater to work two weeks ago. Outside was pleasant, inside was a touch too cool.) I’ll get hot in here eventually, just not yet. And in Fall, it’ll take us a while to cool down, too.

      1. You are spot on about the solar exposure Maggie. I know that here in Canada, many houses are positioned to maximise solar exposure during the winter months and minimise it during the summer, from such features as deciduous trees being planted in from of windows(in summer they provide shade but allow light and heat in winter), to the length of the overhang of the eaves, which also provide shade in the higher sun in the summer, but let light into the house in the winter, when days are much shorter and the sun hangs a great deal lower in the sky.

  7. My understanding* is that this happens because the surface has been weakened by more freeze-thaw cycles than in warmer climes. Pavement is necessarily porous, and ice tends to form in there and break it up over time, and then gives way when the weather heats up and it re-expands.

    *Not and engineer, but I play one on TV.

  8. Used to be when I’d drive past highway construction you’d see a layer of asphalt then concrete, then asphalt on top. But lately most of the highways around here (DFW) seem to have left off the top layer of asphalt and the driving surface is concrete. I have noticed much fewer potholes on the highways since they’ve done this. I asked a highway engineer once about it, but it’s been 20ish years. I recall he said the lower layer of asphalt is to be flexible and cushion the road, the concrete layer is stiff an hard and holds up well, and then the asphalt layer of top was easily fixable. It’s been a while so I could have that wrong, and like I said it appears they build roads different now. But I definitely remember him thinking that Texas’ large oil industry had something to do with us using two layers of oil-based asphalt.

  9. Um, here in Delaware we have expansion capability engineered into the roads, bridges and sidewalks. I guess Minneapolis engineers have not heard of this newfangled “thermal expansion” property most materials tend to have? If a Delaware pavement buckles, the builders are held responsible (unless they are politically well well connected (and not named Capano)) for faulty design.

    We used to have one of the first continuously reinforced concrete superhighways – the 495 bypass around Wilmington – that was engineered to expand and contract as a single, miles-long unit. It was rather impressive until the concrete started to break down at the molecular level after a decade or two. Seriously – the State said it was a chemical incompatibility between the aggregates used – http://pubsindex.trb.org/view.aspx?id=424656 – and the cement itself.

    I recommend Minneapolis hire new highway engineers, ones who have lived in a place with variable temperatures at some point.

  10. I live in Winnipeg, about 450 miles NORTH of Minneapolis, and our streets look like this all the time. We were always critical of the municipal government for doing such a shit poor job of maintaining the streets, because whenever we went to the States, likely Minneapolis, the streets were always pristine in comparison. It’s strangely reassuring to see the streets buckling in Minny just like here at home!

    1. Calgary is worse because of the constant chinook-related temperature shifts, as Winnipeg stays cold once it gets there.

      Although I only have a minor amount of experience with road construction, the buckling could have to do with the difference in temperature between the asphalt, the support materials, and water content of the ground surrounding the highway. It could also be related to the thickness of the asphalt, which can be quite thick in some road designs (12 to 18 inches, I think).

      Here’s a really good resource for research.

      1. Here where we are, it comes down to the thaws that occur with the odd above freezing day that occurs about once a month. The ice and snow turn to water, work their way down into the cracks and crevices, then expand when they freeze. A few cycles of this, and you have the Pothole Capital of Canada! Once spring hits, this is amplified ten fold. Hell, spring is still springing for goodness sake!

        1. True enough! I know that Winnipeg uses concrete extensively to address these issues, but Calgary still persists with conventional compacted backfill.

          Also, if we really knew what we were talking about, we’d be saying ‘sphalt instead of the standard pronunciation.

  11. As a Minneapolitan, I can tell you that most of the people I know weren’t affected by the buckling so much as directly by the heat. Best cycling city in the nation shouldn’t get too hot to comfortably ride!

  12. ” If there’s no place for it to expand to—as in the middle of a highway—it can buckle along the weakest point.”

    Those bumps you hit on concrete roads are expansion joints, thats where the road will expand to in the heat. The picture posted is pavers, not a concrete slab road. That hole in the picture is a tree stump and the damage is due to the settlement of the soil around where the tree stump and root system rotted out. Why does this happen when its hot out? The ground water has lowered, the soil can now settle into the void space left when the water recedes
    out of the soil.

    Damage to the road surface is a sign of the problem in the roadbed. Concrete is far stronger than the stress created from thermal expansion as long as is it constantly supported by the roadbed, road bed fails then the road fails above it, patch that hole a new one will form since the bed is weak below it. A slab will only buckle if it is restrained,roads are not restrained, they are free to expand laterally either to the sides of the road or into the expansion joints that are place in slabs.

    1. If the affected sections of the I-94 were built to AASHTO standards, the roadbeds should be sufficiently compacted to prevent subsidence of the roadway. If the 21 failures occurred around repair work, or sections that don’t conform to AASHTO standards, that could be the cause but that kind of failure usually isn’t referred to as “buckling”.

      If the temperature change above ground is sufficiently different from that above ground, in that the air temperature not only stayed high for a prolonged period of time, but it was previously low enough so that the ground temperature below the depth of the pavement hasn’t had time to absorb enough thermal energy, you could possibly have buckling.

      Also, roads are restrained by ground on either side, and that ground is usually permeable to water. If it was quite wet (i.e. lots of rainfall) prior to the heatwave, the ground would be more rigid and would push back more against the expanding asphalt. Again, if the temperature change from before the heatwave to now occurred quickly enough, buckling could result.

      1. Roadways are not going to have a earthen barrier on the edge that would be capable or restraining a slab enough to buckle the slab, such an arrangement would be a drainage nightmare and serve no real purpose. Concrete is very strong in compression, buckling is a compression failure. HMAC is kind of a pseudo solid, when heated it will loosen and start to flow over retraining edges instead of buckling. As it ages it will become more rigid, but if the HMAC is old, so is the roadbed. Old road beds are not going to support the roadway, which is more likely the problem that will damage the surface.
        I think the problem is a term is being applied that isn’t the correct description of the failure. Slabs could heave in the long direction of the roadway, but this would be limited to incorrect thermal expansion jointing. ANd heaving isn’t buckling. Pot holes, surface cracks etc and indications of problems with the road bed. Freez/thaw cycles damage the surface underneath the road way, once cracks form from this damage the freeze/thaw with open up the top of the defect creating the pot hole.

  13. But what’s up with the picture of a gap left by a tree that has recently been removed from it’s spot in a cobblestone sidewalk? Deformation from decades of root growth is definitely not heat buckling.

  14. Maggie, I hate to break it to you, but if this weather pattern continues, you might see a repeat of the summer of ’87. It absolutely sucked. The 4th of July was 104 or 105 with tropical humidity. You wouldn’t believe the volume of mosquitoes (or maybe you would, little bastards being the state bird, and all). A quick wikipedia check confirms my memory of that summer being the one with the monster 10″ rainstorm. I generally hated getting dragged to the Uptown Art Fair, that year it was positively unbearable. Good times.

    I’d change the location for the meetup to one of the beaches on Calhoon, but that’s just how I roll.

  15. It gets into the 120s here, and we’re on sand and scree, but no buckling problems.

  16. 97 is your record high? In Kansas that’s what we call July. And August is even worse.

    1. Given sufficient funds and sufficient time, the current highway engineers could design and build a highway to last 1000 years of hellish conditions, but given the focus on cost effectiveness they’ve only designed and built it to withstand a certain range of operating conditions for a span of time (guessing 20 to 40 years). Guess what? It’s probably cheaper and easier in the long run to build it that way and deal with the repairs when there’s a 1-in-20 years heatwave, then it is to create a longer lasting roadway, given the local environmental conditions (or at least that’s the approach they’ve taken to it).

      Of course, once the repairs are performed to the buckled sections of road and traffic returns to normal, the public won’t care about highway engineers or what they do or don’t do. In fact, they’ll start asking why they exist at all and why they have to pay them with taxes and/or service fees.

  17. Every state Department of Transportation has an R&D department that researches the best materials for roads, among other things. Ever run across “TEST PAVEMENT” signs on the interstates? Every state tries to make its roads out of material that will be the cheapest for the taxpayer but also fulfill the needs of that state.

  18. Re: stucco houses

    I would presume there is a bit of confusion about what stucco is. Stucco is a render – that is, it’s a clay-based (modern version is cement-based) plaster coating used on the outside of walls. Doesn’t really have much effect on heating or cooling of a house.

    The walls themselves (underneath the render) however, could be brick (common pre-1950s) or standard two-by-four (common post-1950s) construction (or pretty much anything else). Brick walls, if thick enough, will have the thermal mass to keep the indoor temperature reasonably stable in the summer. Can be more difficult to heat in the winter though, depending on if there is insulation on the inside of the walls. Two-by-four homes need lots more insulation to keep comfortable, but are initially cheaper to construct. The stucco on the outside won’t really make any noticeable difference either way.

    And yeah, trees are also great to have around, and will make more than a little difference just on their own!

  19. Hard to tell if the buckling is just the heat, or just the roads locally continuing to fall apart. In Edina, on Gleason Road across Hwy 62, and on Vernon, one needs a four-wheel drive to travel. And of course, Edina claims they have no responsibility… they claim it’s a county road. Then the county would claim it’s a state road, and it’s up to them to fix.

    Yet, the Edina City Council is concerned with new bike paths!

    1. I don’t know anything about Edina or their roads, but hells yeah to their promoting better bike paths! Not enough communities do this, and they are worse off for their neglect. Props to Edina!

  20. This is probably the 100th comment like this, but: 36? 36 is a heatwave? That’s just normal summer. We had a heatwave not that long ago where it was 45-46 for a week and a half on end. Even the big air conditioners in supermarkets couldn’t handle it after that long…eugh.

    Yes, I refuse to use olden days measurements.

    1. Yes, I refuse to use olden days measurements.

      As a non-USian I can empathize, but by all means, go all the way and stop using that olden-days language with its antiquated orthography.

    2. In Toronto today, it’s gonna feel like it’s 42 or 43 degrees C – is that a heat wave, or does it have to hit 50 degrees C before you notice the heat?


      In any case, it is expected to be another record day for temperature.

      1. “Feels like” temperatures are a really strange concept for most of the world… Toronto had 32.6° C at 53% relative humidity. Normal summer temperatures for temperate regions all over the world. Not talking about extremes like the American Southwest or India, just normal temperate climates.

        But yeah, standards are obviously different in different parts of the world. I remember how everybody in Toronto freaked out two or three years ago when they had dry 30° weather with everything from urgent heat advisories to free public pools. This is what happens here when temperatures reach 40°. Never could figure out why the same temperature is more dangerous for people in one region than in another (we don’t have an A/C culture here, so that’s not it ;-).

  21. Yes, I refuse to use olden days measurements.

    If you really want to get ahead of the game you could use the temperature scale that’ll be all the rage when the heat death of the universe rolls around:


    It’s base 10 and absolute! Whats not to love?

    1. those systems have about half the accuracy (have half the degrees) as the old fashion system when you live between freezing and half way to boiling most of the time. Maybe the difference between 88 and 89 isn’t a huge deal, but why I should want to make my system harder to understand just so I know how much warmer, than absolute zero I am, is a mystery to me…

  22. we made the drive back from a canoe trip in northern minnesota that day.the temps up there were cool and stormy.at a rest stop just out side of minneapolis i got out to check the tie downs on the canoe and it was like oven outside the ac car,103 we found out later.almost home at the mississippi river bridge at minneapolis the road crews we just setting up left lane close signs around a section of buckled road.i think the problem is that you can’t make expansion joints wide enough to handle the temp changes from summer to winter,they would be too wide.old cement freeways have expansion joints that create a nasty ..bump..bump..bump for miles when they tried to make large joints..i guess–
    big highway tie up news this AM is a horse on the loose with four lane back up for miles and the state patrol trying to find someone,quick,”who knows horses and has a trailer”
    and by the way the temps are going onto the 60’s in a few days!!!

  23. Wow, Minneapolis was 11 degrees hotter than Palm Springs yesterday. That’s unnatural.

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