MINNEAPOLIS (WCCO) — Extreme discomfort is not the only reason Twin Cities road repair crews have to hate the heat this week. On Monday alone, more than 30 heat-related pavement “blow-ups” were reported in the greater metropolitan area.
Metro crews had to patch one of those spots on Interstate 94 at Lowry Avenue Monday. Then, on Tuesday afternoon, the opposite side buckled.
“We have some of the worst weather you can for building stuff outside. Between hot weather like we have now and the cold we get in the winter, we have extremes on both ends,” said the Minnesota Department of Transportation’s pavement engineer Curt Turgeon.
Highway engineers have a variety of concerns when it comes to the sudden high temperatures. The heat problems roads are having now are generally occurring along the transverse contraction joints of concrete roads. Those are the intentional cracks road-builders create or cut between the slabs of concrete that make up our highways.
“We’ve had a cold, but a wet spring,” said Turgeon. “So, the concrete pavements have a lot of moisture in them. Then we had a very abrupt change in temperature.”
Meaning, the blast furnace of heat that hit Minnesota this week has a lot of moisture that will expand within the concrete.
There are 350 slabs of concrete in every mile of highway and between every slab is an expansion joint.
When the slabs expand to the point they are pressing powerfully together where the joints touch, something has got to give. If the pavement ruptures, it is referred to by engineers as a blow-up.
“It just takes one joint to be not quite as good as it once was,” said Turgeon, to create a blow-up.
Logically, the bottom of hills are more vulnerable to heat blowups because of the weight of the slabs pushing down on each other.
The goal for MNDOT is to have the lane on I-94 re-opened the next morning and a permanent repair made in one to two weeks.