Originally Posted By: dave aber This post was automatically imported from our archived forum.
First let me say I think this is a great site for homeowners to research.
Now...I have a poured foundation(exposed basement) that is approx 10 months old (poured in the winter), and I have noticed a hairline crack running vertical from grade level to the top of the foundation. I first noticed this on the outside basment wall, but then after further evaluation, it is also on the inside wall of my basement and seems to be "off-set" by about 10 inches from the outside. The inside crack also appears wider. By builder is comming to inspect, and stated that they woudl probally use hydrostatic concreate if needed. My main question...Is it structurally sound?
Just a homeowner asking the pros!!!!!!!! 
Originally Posted By: jpope This post was automatically imported from our archived forum.
the concrete cracks.
So the real question is; "What is the severity of the crack?"
Typically, "hairline cracks" are considered normal. The thing to look for is displacement (where the surface on either side of the crack is at different planes), and/or large cracks (separations in the concrete of more than 1/8").
These could be indications of failure of (or lack of) the reinforcing steel.
Also, again generally speaking, horizontal cracks are more indicative of a potential problem.
Here are some pictures of a serious problem.
-- Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
Originally Posted By: Don This post was automatically imported from our archived forum.
Don’t worry about a little crack like that. It sounds like it is normall to me and stuff like this happens. Have your builder patch it up and seal it. Sounds to me like it dryed to fast.
Originally Posted By: Bruce King This post was automatically imported from our archived forum.
When concrete is poured in very cold temperatures, they add calcium to make it set up faster. I believe the amount of calcium equates to the temperature. I have seen concrete poured in 10 deg. F without any problems.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
…
But neither one is a substitute for adequate procedures and protection to keep concrete from freezing. A little off-topic, but just an FYI for those doing more detailed phased inspections this winter (and any other winter ... LOL).
Just my opinion and 2-nickels ... 
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: mkober This post was automatically imported from our archived forum.
Generally speaking, placing foundation concrete in freezing temperatures can be done without serious problems developing if certain precautions are taken, including heating of mix water and/or coarse aggregates, keeping all contact surfaces (forms, rebar, bond faces, etc.) above freezing for at least 24 hours in advance of placement by covering with blankets, and of course keeping things nice and warm after placement with the insulated blankets and possibly even providing external heat. Typically, the hydration process of Portland cement is very exothermic (gives off a lot of heat), so thicker members don’t usually experience freezing problems. But if fluid concrete has been allowed to freeze, the surface usually experiences loss of matrix and will begin to scale and crumble, even giving off a characteristic, uncured “smell.” Rarely will frozen concrete manifest itself with through-cracks in the member, at least in my experience. I’ve personally witnessed many instances of frozen concrete, having been involved as project manager and quality assurance engineer in the heavy civil structures field (bridges) for more than 30 years.
Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
Mike pretty well nailed it. But so did Jeff. Concrete will crack. Period. If you can’t stick a paper in it, don’t worry. If you can just barely stick a paper in it, try to seal it. If it’s bigger than 1/8", you may want to consider getting a specialist in to evaluate it.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
mkober wrote:
Rarely will frozen concrete manifest itself with through-cracks in the member, at least in my experience.
I would agree. The problem is usually the admixtures (like calcium chloride) added to help the concrete set in the cold weather ... which can cause excessive shrinkage, and therefore excessive cracking. I see that happen all the time here in the northeast ... particularly for residential construction where there is usually not strict quality control.
[P.S. ... Mike, glad to see yet another fellow PE here on the board ... welcome ...  ]
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
