Multiple Hairline Cracks in Newer Foundation
Multiple Hairline Cracks in Newer Foundation
(OP)
Residential concrete foundation 8'' x 8' tall pour. Has more than enough steel in it - both horizontally and vertically. Poured about a year ago.
In the last 2-3 months it has developed many hairline cracks all over the place. Seem to be getting more numerous - but not wider.
No signs of settlement anywhere. Exterior brick, drywall, doors etc. are all fine.
Any ideas??
In the last 2-3 months it has developed many hairline cracks all over the place. Seem to be getting more numerous - but not wider.
No signs of settlement anywhere. Exterior brick, drywall, doors etc. are all fine.
Any ideas??





RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
What is the crack pattern? Any faulting? Consistent width? Horizontal or vertical?
RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
f-d
¡papá gordo ain't no madre flaca!
RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
Most drying shrinkage cracks do not occur in the plastic state. You are right that they are tension induced, but that tension is often internally induced, not caused by external load application. Drying shrinkage cracks typically occur within a few days after placement, not while the concrete is plastic.
Plastic shrinkage cracks, of course, do occur in the plastic state. They are rare in vertical placement because the conditions that cause plastic shrinkage cracks are abated by the formwork.
RE: Multiple Hairline Cracks in Newer Foundation
While I am quite familiar with concrete - I am not real good at concrete forensics. Hence my inquiry.
ALL concrete will ALWAYS crack - that I know and advise as such.
But these just really started in the last few months - almost a year after the pour. And there is no obvious reason. Soil test was good. Back fill was good. No cracking in any drywall or brick. Steel was more than required.
Just a bunch of hair line cracks popping up all around?? Some vertical, some horizontal, some at 45.??
No water intrusion - well graded and sumped.
Just weird!!
Bad concrete??
RE: Multiple Hairline Cracks in Newer Foundation
Agreed that internal restraint is a component of the force causing cracking. But I don't agree that most drying shrinkage cracks occur within a few days. It is highly dependent on the w/c ratio. For low w/c ratios, most of the shrinkage occurs early, within the first 2 months, but let the w/c ratio get up to say 0.65, and there will still be a lot of drying shrinkage occurring after a year. In these high w/c concretes, less than half the ultimate shrinkage occurs in the first month.
RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
MikeTheEngineer...can you give a timeline of construction and occupancy? If walls were constructed a year ago, cracks probably developed soon after, but have gotten worse as house is used and "dehumidified" by AC system.
Also, as hokie66 pointed out, residential concrete is often "soupy", resulting in lots of long-term shrinkage.
RE: Multiple Hairline Cracks in Newer Foundation
RE: Multiple Hairline Cracks in Newer Foundation
Poured about 12-14 months ago.
Just occupied in the last 6 months or so. So yes, we did go through a summer in St. Louis of high heat and humidity where I know the AC was probably running full time - mine was.
RE: Multiple Hairline Cracks in Newer Foundation
Can you give me the Readers Digest version of an alkali-aggregate reaction.
While the builder said he used 6 sack concrete, only God knows what was supplied. And if it was far from the plant and I think it might have been and weather hot - it may have been watered down quite a bit.
Seen that before!!
RE: Multiple Hairline Cracks in Newer Foundation
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RE: Multiple Hairline Cracks in Newer Foundation
The following page gives a lot of references. I have never had the displeasure of having to deal with it.
http://www
RE: Multiple Hairline Cracks in Newer Foundation
These forums are just flat incredible
RE: Multiple Hairline Cracks in Newer Foundation
The typical pattern, as hokie66 noted, would be tightly spaced cracks and some popouts where reactive aggregate is near the surface.
I'm still leaning toward reduction in humidity causing shrinkage cracking, based on your description.
Any chance of a photo or two, or a sketch of the crack pattern?
RE: Multiple Hairline Cracks in Newer Foundation
Richard A. Cornelius, P.E.
WWW.amlinereast.com