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The right compaction

Discussion in 'Hardscaping' started by johnquest, Jun 29, 2006.

  1. johnquest

    johnquest LawnSite Member
    Messages: 36

    I've got a question about compaction. I'm doing my first paver job, a patio at 270 sq feet. I put in the base over the past couple of days 5" compacted, two lifts at 3.5" and about 7.75 tons of 3/4 minus crushed concrete. The first lift seemed to compact pretty well. I wet it down good. The compactor I'm using is a rental (Bobcat BC110) rated at 4630 lbs cf. I'm not sure if I got the right amount of compaction on the 2nd lift. I drove a 10" spike with my 3 lb hammer pretty easily. I'm wondering if I can compact again, get the base wetter, and if I should somehow find a more powerful plate compactor? Or if the compaction I have is enough? It has finished off close to perfect with no rises or falls greater than 1/4". And the fines are nicely available throughout the base mixture. It's nice and flat, smooth but I think I need it compacted more. I spent 45 minutes on it with the Bobcat compactor, took it down as far as it would push it.

    I know it's not at the recommended 95% minimum mod proctor density. Or if I were to drive a dump truck on it I'd probably make an indentation. I live in the Midwest (Nebraska). We have freeze thaw cycle but usually the frost goes out in March all at once. How much will less than ideal compaction affect the final job? With a 5" base can I get by with a little less compaction on a patio?

    I'll post some pics of my project tonight

    Thanks, all in advance

  2. Pavers Plus

    Pavers Plus LawnSite Member
    Messages: 83

    it is possible to over compact your base without realizing it. what can happen is the modified stone can become separated (larger to smaller). 45 minutes of compacting for 270sf is pretty excessive. Also, the method of driving a spike through the base for determining density is not always accurate, as different parts of the country have different types of modified stone, which perform differently. In my part of Maryland, I was used to using limestone crusher run, but I ventured out toward the eastern shore and I ordered my normal CR/6 and received a mix of concrete sand and river gravel, which what was also being used on the construction of the nearby street. Needless to say, the spike went in much easier than I was used to.

    The machine you rented should be fine for both your base and compacting the pavers into the sand setting bed. 4600lbs cf is more than the majority of contractors are using. Hope this helps.
  3. johnquest

    johnquest LawnSite Member
    Messages: 36

    Thanks, Paver Plus. Now that I think about it. I didn't compact that long. But the compaction seemed instant the moment I brought the compactor up to full power. I went over the base in a circle from edge to center then north to south twice and east to west twice, then over the corners again the best I could. I can see how nice a compactor with reverse would be. I think I'm probably fine but checking in with the pros can't hurt since this is my first patio. Stay tuned for some pics.

  4. johnquest

    johnquest LawnSite Member
    Messages: 36

    Here are a few snaps of the project. It's hard to photograph compaction but the surface can be seen. There's also a few here from the start, geofabric, and finishing putting in the last lift. I used a pitch line I moved with me as I put in the base and a 2x4 to hold it in 18 inch sections, both lifts.

    Please comment on anything you see. This is cool work and I'd like to learn more.

    Thanks, all






  5. lawnboy

    lawnboy LawnSite Senior Member
    Messages: 321

    what is the plastic for? Never seen anyone do that
  6. Gilla Gorilla

    Gilla Gorilla LawnSite Senior Member
    Messages: 923

    I LOVE the finished look in the last picture.

    Just Kidding
  7. johnquest

    johnquest LawnSite Member
    Messages: 36

    The plastic or the geotextile? The plastic is just tarp I have over it. The black stuff is Mirafi geotextile.
  8. kris

    kris LawnSite Bronze Member
    from nowhere
    Messages: 1,578

    First off John I think you are probably FOS and this is not your first paver job but I will play along just for fun .... first mistake ... you did not compact your subgrade. rip it out and start over:waving:
  9. johnquest

    johnquest LawnSite Member
    Messages: 36

    Why would you think I didn't compact the subgrade? That's a no brainer. Of course I compacted the subgrade. What do you see in the pics that says otherwise? I have no idea why you think this isn't my first paver job. Can you be constructive? My post is asking for advice on compaction and whether or not I should try to get the base compacted more.
  10. cedarcroft

    cedarcroft LawnSite Senior Member
    Messages: 442

    not to speak for someone else but he probably is saying that because based on the pics and your post, it sounds like you know WTF you are doing. I would say you took a class or did alot of reading and it looks like you are starting out the right way. But then again, I don't know sh!t.

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