Replies

1. 
   dnjan | Jan 02, 2004 10:36pm | #1

   Once the concrete has cracked, it cannot be "glued" back together so the crack doesn't show. 

   I assume the crack has opened to at least 1/16" or more in width?  That would be a normal shrinkage crack.  Those can't be prevented, but instead are normally hidden by the correct use of control joints.  One problem with trying to fix the crack is that the concrete will continue to shrink as it dries.  So any "fix" will just re-open.

   When you say that the company that did the placement did it incorrectly, what exactly was incorrect?  Did they omit the control joints?  Did they tie the slab into the foundation walls?

   Cracks can be epoxy-injected (gray epoxy can match concrete color pretty well), but this doesn't mean that the crack won't re-open when the house is finished and winter heating dries the slab even more.

2. 
   OracleDesign | Jan 03, 2004 12:03am | #2

   Let me quote Joseph Lstiburek, author of Builders Guide to Mixed Climates. Details for Design & Construction. He stated "Concrete cracks. Concrete has always cracked. Concrete will always crack."

   We built our entire house with the intention of having all stained concrete. We made every effort to minimize cracking, but we knew going into the project we would get cracking. We opted not to have any control joints for aesthetic purposes. We used an abundance of deep footers, piers to bedrock, and plenty of rebar. We simply viewed the cracks as adding a dimension of character to the stained floor. I will say that I think it’s best to crack before staining so that the stain "incorporates" into the crack rather that than cracking after the stain.

   All of this being stated, I assume that the crack in question is simply one of normal shrinkage and not structural in nature. Make the best of what you have. Good luck.

1. 
   brownbagg | Jan 03, 2004 01:22am | #3

   Concrete will not always crack, I have proven this over and over,. Cracking is a by product of poor workmanship. Its a excuse that all concrete will crack.

   But the purpose of this post is. I have stain concret in my house too. The screw ups make the slab that much better. I have a foot print in mine. The crack will make it look like marble Alot of marble I have seen as crack or veins.You can make the crack less noticable by saw cutting or go with a darking stain. maybe a two tone like a light tan with a dluted cloudy black on top.

   If you still convince that all concrete crack, go ask Gable

   The best employee you can have but you wouldn't want him as a neighbor " He the shifty type"

1. 
   sungod | Jan 03, 2004 02:10am | #4

   I know why concrete cracks, I know how to prevent cracks,  I know what guys do to prevent cracks.  But there are things that are out of your control.

   Not all loads of concrete cure the same, one load will not do the whole slab.

   If part of the slab is in the sun and the other is shaded, it will crack.

   If water is added to the mix so it can be pumped, all mixtures have too much water and so it will shrink.  Hardest / strongest concete has almost no water added.

   I do know a guy who will promise no cracks, he charges twice as much and has jackhammered a few to back his promise.

1. 
   DavidThomas | Jan 03, 2004 02:31am | #5

   "promise no cracks, he charges twice as much"

   And therein lies the problem, right?  Do you go with the low bid?  Or with the high end guy?  Extra re-bar (on dobies!), WWF, fiber-mesh, etc.  Meticulously prepared base.  If not a cloudy day and 50-65F, send everyone home and reschedule.  After the pour, keep it wet for a week.

   But no, gotta save money.  Stay on schedule.  Add calcium and use hot water in the winter.  Or pour on a hot sunny day.  Add water instead of wheelbarreling it around.

   There's a natural order to:  Letting the ground thaw, pouring the slab in early spring, framing in late spring, work in the shade of the house/roof in the summer.  Get the heat going before late fall.  Do the interior work.  And yet, reasonably enough, people in all the trades want a paycheck year round.  And clients - Jeez - sure you can break ground (literally) in January.  But the fit and finish won't be the same.

   They make fricking concrete boats.  Boats!  So concrete does not have to crack.

   I'm not pure.  I've done all of the above.  But within limits and accepting the consequences.  (And only on houses.  Not on boats.)David Thomas   Overlooking Cook Inlet in Kenai, Alaska