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The Mysteries of Road Repair

Reader Steve wants to know:

Do you know why there is always a delay, sometimes of weeks, between the scarification of a road surface and the repaving? In my experience, this occurs regardless of whether the project involves a low volume city street or an interstate highway.

Any infrastructure types out there care to weigh in? Is it part of some carefully planned process, or just lack of coordination between the scarification guys and the paving guys?

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This entry was posted on Monday, August 17th, 2009 at 7:24 am and is filed under Roads. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

6 Responses to “The Mysteries of Road Repair”

  1. Vincent Clement Says:
    August 17th, 2009 at 8:59 am

    Not an ‘infrastructure type’ but I have noticed that, sometimes, the scarification reveals that the layers are crumbling or cracked and require additional repair, delaying the repaving.

  2. Greg Says:
    August 17th, 2009 at 9:33 am

    There isn’t always a delay. Several weeks ago, the city of westminster, ca ripped up about a mile of a major 5 lane street one day and then repaved the next. That included some curb and gutter work as well. I ride my bike to work and I was dreading the expected multi-week riding on the scar’ed surface, but they re-paved within a day.

    So it can be done. The possible delay may be city/county/state involved do to inspectors. Just a guess though.
    BTW - just got the paperback version of your book. Very entertaining and educational read.

  3. JJM PE Says:
    August 17th, 2009 at 10:03 am

    Sometimes it is simply a scheduling conflict between the miller and the paving crew.

    One process, called cold-in-place recycling, requires a certain amount of time before paving. The existing pavement is ground up for a depth or 6 to 18 inches, a stabilizer is added in, and a new surface is placed on top. The stabilizer is often asphalt emulsion, which is a mixture of liquid asphalt, water, and emulsifiers which allow the two dissimilar materials to mix. Over the course of a week or two, the water evaporates, allowing the asphalt that remains to bind the particles together. Once the water has evaporated, a layer of asphalt or a chip seal is placed on top to keep rainwater out and provide a wearing surface.

    This eliminates the cracks in the existing pavement, which would soon crack through the new top layer if the highway department just paved over the existing road. It provides most of the benefits of full-depth reconstruction at a fraction of the cost.

  4. Fritz Says:
    August 17th, 2009 at 3:21 pm

    We only notice the delay when it’s *ahem* delayed.

    If the road is milled one day and repaved the next, you hardly remember it, especially if the milling was done in the middle of the night after you’ve gone home for the day.

  5. Bossi Says:
    August 17th, 2009 at 5:36 pm

    Numerous issues can be at hand. Funding may be diverted, there might be a scheduling conflict between millers & pavers, an asphalt company might stop doing business, etc… The first one doesn’t typically happen while a project is under construction, but in this economy I wouldn’t rule it out. The latter two are very very real possibilities & happen very very often.

    While in most cases I have faith this isn’t the case, there’s a small chance it could be a low-bid contractor that just… well… sucks. Generally contractors are pretty good at what they do, but every region has at least one notorious company.

    Different paving methods may also be at play. JJM PE noted cold-in-place recycling. Some states are experimenting with white-topping, which instead of throwing down 2 inches of asphalt & letting traffic on a couple hours later; now it’s several inches of concrete that needs a couple days to cure.

    In States with lots of roads, little population, and a bureaucratic system whereby one agency is responsible for most of said roads (Pennsylvania comes to mind), it could also be a cost-cutting measure for the contractor. Essentially, the contractor has his start date & end date… the end date gives quite a bit of flexibility, so the contractor might use that extra time to send the crews to another, more pressing, project. This flexibility benefits the contractor by letting them multitask their crews, it benefits the State by cutting costs, and it benefits the public by letting their taxdollars go further… so long as they don’t mind staring at a line of orange barrels reaching out to the horizon with nary a worker in sight. Orange barrels eventually become just a part of the roadside landscaping. :P

    Flexing crews around is also, to some degree, at play even when tasks aren’t contracted out. An agency’s in-house crews are often stretched out, too… so they might just tear up a failing surface & leave it milled whilst they move on to take out another failing surface… eventually coming back once they take out the more severe issues.

    It could be that lower layers in the pavement were more damaged than anticipated, but generally data sampling catches this beforehand. In some cases, keeping the milled surface is used as a traffic calming measure… though I’m not entirely sure its real impacts have been too significant; and surely not worth the noise. And sometimes special types of milling may be used to improve friction or to create rumble strips/stripes… I’ve run into a number of people who confuse a milled roadway with standard milled rumble strips.

    I’m sure there are a multitude of other reasons… but there’s a few to get you started. Cheers!

  6. Wes Says:
    August 21st, 2009 at 11:13 am

    In relatively rural cities, such as ours, contractors make arrangements and appointments for many projects. There are occasional shut-downs and problems at the asphalt plants, and of course delays occur; but normally the delay is very, very short. Contractors lose money when equipment sits idle.

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