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[DriverDave]

What is the "Echelon" paving technique? Supposedly it is a state of the art method of paving highways that results in "better bonding" and thus a longer lifespan. Apparently this is what was used to build the Texas state highway 130 with the 85 mph speed limit. What would be the economic costs of using this technique to fill potholes/fix more highways with it? From what I've read online this only applies to asphalt surfaces?

[kphoger]

Echelon paving is when two paving machines run at the same time, each doing one lane, with the second machine staggered slightly behind the first.  This way, the longitudinal joint between the two lanes is nearly nonexistent, because the first lane's edge hasn't totally set yet when the second lane's edge overlaps it.

[kalvado]

When using the process known as echelon paving (two pavers run staggered in adjacent paving passes), construction of the longitudinal joint is changed so that the compaction of the unconfined edge of the first lane is delayed until the second pass is placed. Once the asphalt from the trailing paver has been placed against the edge of the asphalt from the leading paver, the hot seam and second pass is compacted at the same time leaving an almost undetectable joint.

It is not about potholes, it is a method for creating better seam between lanes. Would probably improve that area a bit, but seems a bit oversold.
Apparent drawbacks include more equipment on site - at least 2 pavers; and  the need to close at least 2 lanes (more like entire width of the road, 2 or more lanes)  for paving.
A picture of 3-lane run:

[7/8]

To add to kphoger's post, the benefit of echelon paving is that it (more or less) eliminates the longitudinal joint, and asphalt joints tend to be areas of weakness (moisture can seep in and cause damage especially in freeze-thaw cycles). The downside is extra cost of having multiple pavers, and it typically requires a full road closure.

It seems in the Region of Waterloo, the preference is to use echelon paving for surface asphalt, but not for base asphalt. It's challenging to use echelon paving in base asphalt if traffic needs to be maintained during construction.

[kphoger]

Of course, having both lanes closed wouldn't have been an issue there, because they were building the highway from scratch.

[DriverDave]

To add to kphoger's post, the benefit of echelon paving is that it (more or less) eliminates the longitudinal joint, and asphalt joints tend to be areas of weakness (moisture can seep in and cause damage especially in freeze-thaw cycles). The downside is extra cost of having multiple pavers, and it typically requires a full road closure.

It seems in the Region of Waterloo, the preference is to use echelon paving for surface asphalt, but not for base asphalt. It's challenging to use echelon paving in base asphalt if traffic needs to be maintained during construction.

So it's similar to how they build sidewalks with cracks to account for expanding/contracting concrete. Just with asphalt instead?

[kphoger]

Imagine if you took a rolling pin to a slice of sandwich bread to flatten it out on the countertop, then popped it in a hot oven for a minute, then laid another slice of bread next to that one and flattened it out with a rolling pin too.

Now imagine that, instead, you slightly overlapped the edges of the two bread slices and took a rolling pin to both of them at the same time and popped them into the oven at the same time for a minute.

That's kind of what I'm getting out of the information I see.

[7/8]

To add to kphoger's post, the benefit of echelon paving is that it (more or less) eliminates the longitudinal joint, and asphalt joints tend to be areas of weakness (moisture can seep in and cause damage especially in freeze-thaw cycles). The downside is extra cost of having multiple pavers, and it typically requires a full road closure.

It seems in the Region of Waterloo, the preference is to use echelon paving for surface asphalt, but not for base asphalt. It's challenging to use echelon paving in base asphalt if traffic needs to be maintained during construction.

So it's similar to how they build sidewalks with cracks to account for expanding/contracting concrete. Just with asphalt instead?

You're right that for sidewalks (and concrete roadways), joints are installed on purpose for expansion and contraction to reduce cracking and heaving. However, for asphalt, it's better to minimize the number of joints. My understanding is that concrete is "rigid" pavement whereas asphalt is "flexible" pavement, so asphalt has better capacity to handle expansion and contraction without joints.

Imagine if you took a rolling pin to a slice of sandwich bread to flatten it out on the countertop, then popped it in a hot oven for a minute, then laid another slice of bread next to that one and flattened it out with a rolling pin too.

Now imagine that, instead, you slightly overlapped the edges of the two bread slices and took a rolling pin to both of them at the same time and popped them into the oven at the same time for a minute.

That's kind of what I'm getting out of the information I see.

Yes exactly. The overlap between asphalt paving should be done regardless if echelon paving is used, but the hotter asphalt temperatures in echelon paving make for a stronger bond with no visible joint.

[kalvado]

Imagine if you took a rolling pin to a slice of sandwich bread to flatten it out on the countertop, then popped it in a hot oven for a minute, then laid another slice of bread next to that one and flattened it out with a rolling pin too.

Now imagine that, instead, you slightly overlapped the edges of the two bread slices and took a rolling pin to both of them at the same time and popped them into the oven at the same time for a minute.

That's kind of what I'm getting out of the information I see.

Well, width of the road is much smaller than length, so thermal expansion is more problem length-wise than across.
And I believe using viscoelastic tar is what takes care of thermal expansion in asphalt - and why it's an issue with solid concrete.

[DriverDave]

Is it true that Asphalt has better traction than concrete? Weird as I've always thought concrete was rougher.