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starrider 06-28-2007 01:10 PM

sidewalk cement?
Hello folks...!

The question: hair line cracks in newly poured sidewalk?

In this city...the home owner is responsible for the sidewalk that surrounds their house.

The sidewalk needed i contracted a co. and did the about 6 yards of cement or concrete of sidewalk...4-5 weeks later i notice a hair line crack about 2 feet in lenghth.

Living in a Bay city...sand was and near the ocean...sand is under the cement. And it was not packed down as i later found out is one of the things to do.

Secondly the crack is within a ten feet of a large old tree..."roots"? However i was told that 5 weeks is not enough time for roots to effect the cement.

Lastly...could it be the cement it self? As when the finisher was doing the sidewalk ...he commented that the cement was funny or didn't seem to have the water amount he was accustom to...( i think)

Otherwise the finisher did an excellent job...and i am happy if the crack does not progress.

My last question is what is the best way to deal with hairline cracks...what are the best kinds of things to use...i was thinking of just pouring epoxy in the crack ....

Your opinions appreciated...Thanks!


timmy 07-10-2007 09:11 AM

Sorry to hear your troubles, please excuse my ignorance, but do your sidewalks have sawed out sections so it can expand and contract without cracking, did they saw any?

Epoxy should be fine, I'm pretty sure thats what our city uses, and I'm sure your city uses it on your roads for cracks.

Best of luck

mudmixer 07-10-2007 11:39 AM

Sounds like a typical shrinkage crack that has essentially died out. There may be others that are smaller that may show up later. The cause of the crack is not having control joints sawed or cracked at appropriate spacings. Concrete will always try to crack, so you control where the crack occurs. - The more cement and water in the mix, the more it shrinks and can crack.

Why do you want to fill the hairline crack? - You will not be keeping water out.

Deacon 07-11-2007 01:09 AM

There are only 2 guarantees in the concrete business -- 1. It will get hard and ----- 2. It will crack. Just as long as there was proper rebar/wire installation installed within the pour and the rebar/wire is within the pour and not just laying on the ground, the hairline crack should be no worry because the steel will hold it together. Some contractors use wire - wire is better than nothing but does not have the tensile strength that regular rebar has. A good concrete prep job consists of No. 3 steel bars installed in a 18" grid. As far as only sand underneath the concrete pour, having 1 3/4" rock is much better but that depends on your individual building code. Again, no matter what you do, concrete will crack. Mother nature always wins. All you can do is try to fight her back as much as possible.

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