When can I drive on new concrete?

Discussion in 'Workshop and Home Improvement' started by RavenTai, Sep 4, 2009.

  1. RavenTai

    RavenTai

    Messages:
    6,085
    Location:
    Dixie co. Florida
    Had a slab poured a few days ago, The guy that did the work said 3 days before driving on it, need to work on the 62 it lost a brake line don't want to crawl in the dirt to work on it but I do not want to mess up my new work surface either. tomorrow morning will be three days, but have been reading online about curing concrete and there are all kinds of opinions, anywhere from 4 days to 3 weeks,

    Anybody have any good info? will i damage it if I drive on it? I figure I will deflate some to reduce ground pressure but still worried about it.


    It is 12'x20'x4" with not much of a perimeter footer, one number 4 bar around the perimeter, no wire but has fiber in the mix and a metal key way in the middle, IIRC he said it was 3K psi concrete.

    another question I have been spraying it down couple times a day keeping it moist, how long should I keep doing that?
  2. Joe_E

    Joe_E

    Messages:
    3,321
    Location:
    the NJ word..
    That's a nice size slab.
    If it were me personally I would wait 5 days to drive a heavy 62 on it . I would also keep wetting it for a week. Keeping it moist makes it cure slower.
  3. bkfj40

    bkfj40 SILVER Star

    Messages:
    2,631
    Location:
    shenandoah valley, va
    For most of the concrete that we test locally here in Virginia and PA, I've seen the 3000 psi mixes reach strengths in excess of 4000 psi after 28 days. Typically, you'll be at 75% of the strength in 7 days and 50%-75% in 3 days. keep it wet for a week.

    With that said....it's a freakin brake line. Do you want to waste all the money you just spent on that slab to work on it? Go buy a blue tarp and work on the dirt....you'll be much better off.

    :grinpimp:
  4. mminter1973

    mminter1973

    Messages:
    440
    Location:
    alabama
    I just poured 180yrds of 4000psi 6" thick and my guy told me one week. I waited 2 weeks just to be sure because many $ were invested!
  5. RavenTai

    RavenTai

    Messages:
    6,085
    Location:
    Dixie co. Florida
    Thanks for the tips, I'll let that slab rest some more and keep wetting it. I have some cardboard to spread on my dirt driveway and work from that.

    With my 62 it nothing is ever as easy as it should be especially around the rear axle, it was a yankee vehicle and most of the metal is trying to return to iron ore, its the longer hard line on the rear axle that rusted through been soaking all the clip hardware in PB blaster for a few days hopefully with that and heat all either turn loose or break off.

    Had this slab poured at the new place to have a work surface, I live on a dirt/crushed limestone road, have sand driveway, nowhere to put a floor jack. already thinking about putting a car port over it, it rains a lot here.
  6. nspctr1

    nspctr1

    Messages:
    2,197
    Location:
    San Antonio TX
    More likely than not it wouldn't damage the slab however, it will probably get dirty from grease and brake fluid and make the wifey mad. Use a mexican creeper (cardboard) and work from the dirt....
  7. Very good advice here. I would also vote for waiting at least 7 days and keeping it wet at least 7 days to minimize shrinkage cracking.
  8. RavenTai

    RavenTai

    Messages:
    6,085
    Location:
    Dixie co. Florida
    Glad to see solid consistent info here on mud, there was all kind of conflicting stuff on the web about concrete.


    You say at least a week on the wetting, Joe said similar, is there any advantage to wetting it longer?
  9. fsusteve

    fsusteve

    Messages:
    3,813
    slows the curing process, the slower the cure the stronger the slab.
  10. Yes, I kept my last driveway wet for 2 weeks, and it had reinforcing wire and fibermesh in the mix. The slow cure does help with strength but it really helps with minimizing shrinkage cracks. I put polyurethane sheeting on top and kept it wet periodically underneath with a hose, FWIW (but I'm married to a degreed civil engineer!).
  11. fsusteve

    fsusteve

    Messages:
    3,813
    I can tell you that pouring a slab in Fla means you'll have some cracking, relief cuts help but you'll still get some.

  12. Pin_Head

    Pin_Head

    Messages:
    11,619
    Location:
    OC, CA
    12 x 20 and no re-wire or rebar? A slab that big is going to crack and when it does, you don't want the joint to separate or take off in different directions. Rebar or re-wire is cheap.
  13. fsusteve

    fsusteve

    Messages:
    3,813
    My slab for parking was bigger than that no steel, but it had fibermesh and expansion cuts, not one crack outside of the cuts in 5 years and it was poured on top of fill.
  14. Joe_E

    Joe_E

    Messages:
    3,321
    Location:
    the NJ word..
    All big slabs regardless of rebar or wire need relief cuts or expansion joints. Smart to have both but the slab needs a place to crack and if laid down properly they will crack in the relief cut every time which is where you want it. Simply fill the cut with caulk after the crack occurs to keep it concealed and keep out excess moisture.
  15. RavenTai

    RavenTai

    Messages:
    6,085
    Location:
    Dixie co. Florida
    As I said, it has one #4 rebar around the perimeter fiber in the rest no wire.

    In the middle he put what he called key way, a piece of sheet metal that makes kinda like a mortise in one half that fits in a tenon of the other supposedly it will crack along it forming two 10 x 12 slabs but interconnected by the mortice/tennon so neither will shift to make an uneven surface.

    looks like this:
    [​IMG]

    I have never seen this used before. we will see how it goes,

    So far so good, 5 days, been keeping it wet and no cracks, not even at the keyway, yet, I guess that will happen when it dries out? hopefully after it has generated most of its strength to keep them to a minimum.
  16. 45Kevin

    45Kevin

    Messages:
    1,754
    Location:
    Calgary, Alberta
    Interesting stuff. I just had my driveway poured with 3k psi. I used 1/2 re bar on 2' x 3' centers and the slab was poured on 3 to 4 inches of unwashed gravel. I haven't been on it yet (two weeks) because we may stain it darker and don't want to dirty it up.

    The finisher said wait at least 3 days. I have never heard of wetting the slab for a week or two. We don't get a lot of heat up here though.

    The drive is about 40x10 and I have control cuts about every 8 feet.

    mminter, what the heck are you building with 180 yard of concrete. My drive way was barely 4 m3. We don't measure in yards anymore. 1 m3 covers about 100 sf at 4 inches thick.
  17. Joe_E

    Joe_E

    Messages:
    3,321
    Location:
    the NJ word..
    That's a nice system as well. It's purpose is to be an expansion joint yet the shape will keep the two slabs locked and not allow one or the other to raise or lower independently.
  18. That's what I used on our last house driveway as well. It's a good system.
  19. titanpat57

    titanpat57 SILVER Star

    Messages:
    1,837
    Location:
    Hudson Valley, NY
    Where's the frost line in florida Steve?......................:grinpimp:
  20. fledglingme

    fledglingme

    Messages:
    85
    i've never heard that water slows the cure time. water assures that the chemical process in the concrete , isn't interupted because of lack of h2o.

Share This Page