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Thread: Highway Grinders

  1. #1
    Senior Member RoadDoc's Avatar
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    Arrow Highway Grinders

    Here is an update on the PCC pavement repair projects in Louisville, KY. The patching is moving along. They are far enough along to start the diamond grinding and joint seal operations. Here are some shots of the four foot grinders they are using. There are currently nine (9) of them on this project! Two contractors, Safety Grinding and Grooving out of Napolian, OH and Penhall/Highway Services out of MN. Lots of big iron.... Lots of water....Lots of slurry!
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    Senior Member JDOFMEMI's Avatar
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    The roads sure are nice to drive on after they grind them smooth. Too bad the hiway departments did not figure out how to do this years ago.

    The road has to last longer without the added impact of trucks going over the bumps.
    Not to mention less wear and tear on all of our cars and trucks.
    Jerry

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    Senior Member RoadDoc's Avatar
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    Arrow More....

    Diamonds......Blowers......
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    Senior Member bill onthehill's Avatar
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    They are doing that on I-390 from Rochester,NY to Corning. It makes an incredible smooth surface. Are they coating it with anything? Pa. has been doing some bridge decks and then applying a seal of some kind over the ground surface. It seems to be holding up good for over a year now on rt 15 where there is a lot of truck traffic.
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    Senior Member RoadDoc's Avatar
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    Hi Bill:

    No sealing here. I've ground bridge decks in GA and followed with an epoxy overlay (Polycarb) before but thats the only sealing I've seen done after grinding. Who has that contract, do you know? Wonder if my old friends at LC Whitford are in on it.

    Hi JDOFMEMI:

    I agree. The ride difference from before to after is significant. You're right, a good grinding regimen can extend the life of a road by many years. I've rehabed pavements that are reaching fifty years of extreme service without a reconstruct. You just got to stay on top of it with a good maintenance schedule. The fewer bumps and less slab curl you allow to happen, the longer the life you'll get. Must pay attention to drainage issues as well, of course.
    Last edited by RoadDoc; 07-25-2009 at 11:48 PM.

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    Senior Member RoadDoc's Avatar
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    Arrow More.....

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    Senior Member D5G's Avatar
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    Nice pics, looks like a big operation!

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    Senior Member AtlasRob's Avatar
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    Great pics RoadDoc but its all a bit foreign to me

    Am I correct in they actually grind the concrete road ? If so why/how has it become so uneven? I have trouble imagining that a concrete road will have worn grooves in it, but that is the feeling I am getting.

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    Senior Member RoadDoc's Avatar
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    Exclamation Get Ready......

    Why do we grind........

    Allow me to elucidate.

    AtlasRob, I know you have experience with a concrete paving train from the Air Force runway pictures you posted.

    What happens after that is a normal process of concrete curing and wear and tear from usage. The paving train covers the reinforcement and joints are cut in over the load transfer baskets to allow for controlled cracking. There can be expansion joints involved as well, however, you don't put many in an interstate highway. Because you have cut a joint in the slab surface, you have created a location for differential cooling of the concrete during the curing process. The area around the joint will cool faster than the rest of the top of the slab unless you go to extreme measures with a full blown water cure that usually is not possible when building miles of road. Water evaporates quicker at the joint during hydration as well. It's like a cake falling when you take it out of the oven, sort of.... Anyway, you get "slab curl." The arch enemy of all concrete pavers! Slab curl allows a hump to form at the joints. The joints are then subjected to massive impact loading under traffic. Especially todays traffic loads which are probably double or more of what the design loads were in the fifties when the interstates were designed. So the concrete at the joint fails.....

    There are other reasons to grind. Subgrade failure, frost heave/settlement, poor drainage under the pavement, and even rutting (yes even in concrete) in the case of insufficient aggregate strength.

    Point is, nothing is designed perfect from the start. There are too many variables out in the world. I'd like to think that observant and consciencious contractors and engineers would make adjustments in the field during construction. There are probably too many variables to build a concrete road that's perfect. Asphalt roads will have their own issues as well.

    The upside is that concrete pavement can give you an extremely long and productive life cycle cost benefit. Usually the first 20 years of a concrete interstate require no maintenance whatsoever. Secondary roads may go as much as 30 years. Pretty good.

    Grinding is one of your maintenance options early on. It eliminates slab curl. All a grinder does is act as a large straight edge that eats off the high points that pass under it. By eliminating the bumps, the road becomes smooth again and there is no more impact loading. This extends the life of the pavement. A few years later, you go in and repair cracked and damaged pavement and possibly grind again (usually not). Then in a few more years, you do a rehab. Remove bad concrete, grind everything, and reseal all the joints. You can do this for quite a while. Eventually, slab thickness will dictate a reconstruction. By then you should have in the neighborhood of fifty years of service from the pavement. The key is to stay on top of the impact loads and drainage issues. Most times those issues are tied together to cause the problems you are seeing.

    Or..... You can do like a lot of Highway Departments and just pave over it with asphalt.

    Thus, we grind.

    Last edited by RoadDoc; 08-01-2009 at 03:26 PM.

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    Senior Member JDOFMEMI's Avatar
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    Roaddoc

    You missed one other leading reason.
    Some concrete paving, especially that found here in SoCal, was paved with waves in it to start with. This was done many years ago when the technology was not quite there yet to grind it smooth, so it was left. Many of out freeways here had that problem. I think it mainly depended on the quality of the original paving contractor. Much of the I-10 froom LA all the way to Palm Springs used to jar your teeth out in any kind of vehicle. It had nothing to do with swelling joints that you described, just a wave about every 4 to 6 ft, and nearly 1/2 inch in the worst places. The joints had developed the issues you spoke about, but it was rough all over.

    Much better now that it has been ground.

    Also, there were many areas here without the dowels between slabs in the older construction. In these areas the individual slabs were "floating" on the subgrade.
    Many of these areas have had dowels retrofitted, then ground smooth.

    The ride is much better here in SoCal after 4 or 5 years of grinding projects.
    Jerry

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    Senior Member RoadDoc's Avatar
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    Thumbs down Aggregate Lock

    Jerry:

    Thanks for your input. Would like to see what you've described about the waves in the pavement.

    I know there was a school of thought once upon a time that large sized aggregates would take the place of reinforcing. At the joints, load was to be transferred by "aggregate lock." Problem was the cements at the time were not up to the job and you'd get delamination of the bond between cement and aggregates. Followed by movement of the aggregates themselves and allowing more water into the joint.... Recipe for a rehab. In fairness, the roads still lasted a long time. I know for certain you don't want to buy the diamond blades it takes to saw those old pavements. They are HARD.

    Dowel bar retrofit is something I personally have not had the chance to be a part of yet, therefore, don't know a lot about it. Looks like a strong contender for maintenance work in the future. Appears to be most popular in the midwest and, based on your report, out west.

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    Senior Member AtlasRob's Avatar
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    WOW ! I think I just gone and got me an edumacation duck pilot suffers information overload

    Thank you very much RoadDoc. You explained it perfectly.

    Over here we have played with concrete carriageways but many have now been resurfaced with blacktop due to noise issues, and never stretched to the sort of distances you have in the States.

    The main problem we seem to have had is where the individual slabs have moved due to poor ground prep and higher loading than the pavement was originally designed for, this movement then allows water into the joints which rapidly increases the formation deteriation and allows the slabs then to start pumping with each truck that crosses it.

    I believe there is a similar problem with our runways but maybe they were deliberately designed so that seperate sections can be replaced.
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    Senior Member bill onthehill's Avatar
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    Doc, they are doing a lot of the dowel bar joint repairs around here lately. both NY and PA. are working on rt15 rehabbing the newer portions and rebuilding some of the old stretches to become I-99 when they are finished . LC Witworth is doing some bridge work but I have not seen them grinding. Went by their yard the other day and there are a ton of precast bridge beams stacked up there. I believe they are pouring them at their plant in Wellsville,NY behind their yard and leasing offices.
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    Senior Member RoadDoc's Avatar
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    Thumbs down Joint Failure

    Quote Originally Posted by AtlasRob View Post

    Over here we have played with concrete carriageways but many have now been resurfaced with blacktop due to noise issues, and never stretched to the sort of distances you have in the States.
    Ah yes..... The noise issue. Asphalt advocates (mainly those that sell it and supply their aggregates) claim that concrete roads generate more noise pollution than asphalt...... Perhaps this is true. Of course, those in the concrete pavement industry counterclaim that their product is "green" due to the fact that concrete does not absorb heat from the atmosphere like mean old asphalt...... The debate rages on. I get a good paycheck by working with both. However, one will not find the RoadDoc playing around any asphalt spreads. If you do, you know he is hard up for the $$$. That there stuff is HOT..... And STINKY, too!

    Quote Originally Posted by AtlasRob View Post
    The main problem we seem to have had is where the individual slabs have moved due to poor ground prep and higher loading than the pavement was originally designed for, this movement then allows water into the joints which rapidly increases the formation deteriation and allows the slabs then to start pumping with each truck that crosses it.
    #1.....Always........Drainage, Drainage, Drainage, Drainage....
    #2 Maintain joints seals religiously. (Just like church, once a year....min. Or if you are really good....Xmas and Easter)
    #3 Drainage, Drainage, Drainage, Drainage.....
    #4

    I think you may gather, AtlasRob , we have the same issues here.......

    Quote Originally Posted by AtlasRob View Post
    I believe there is a similar problem with our runways but maybe they were deliberately designed so that seperate sections can be replaced.
    Most generally are. I've worked on apron repairs a good bit. You just take the bad squares out..... The difference being they are 18" thick or more!

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