Concrete shrinkage
Concrete shrinkage
(OP)
Does anyone have some insight on non-structural, 4" conc. SOG in residential structures shrinking appreciably even after 10-15 years since placement?
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RE: Concrete shrinkage
There are some conditions that could cause this....if the concrete were sealed from outside drying influence, then the conditions changed after 10-15 years such that initial drying shrinkage that was delayed by sealing could then take place...you get cracks to widen.
RE: Concrete shrinkage
RE: Concrete shrinkage
For your own observation, most commercial concrete is going to be placed with a w/c ratio that exceeds 0.50. As the w/c ratio increases, so does shrinkage...both short term and long term. Take a look at control joints that are cut into concrete slabs. When cut, there will be either no crack below the cut or a very tight crack below the cut. Check it at 7 days, 28 days and 6 months...you'll see that shrinkage doesn't stop at 7 days.
RE: Concrete shrinkage
Assuming the visible evidence of the shrinkage is cracking, are you sure it is due to shrinkage? Could it be due to thermal effects, ground movement, or a combination of all three?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Concrete shrinkage
It is my house, which I have owned for 8 years, and it is a frequent issue with houses that I inspect for realtors. The place where it is most visible is a in the family room where it is ceramic tile.
RE: Concrete shrinkage
Kieran
RE: Concrete shrinkage
There is a lot difference in moisture here, what with 7 months of no rain.
RE: Concrete shrinkage
RE: Concrete shrinkage
What do you mean by "faulting"?
RE: Concrete shrinkage
OK I think faulting is where the crack propagates zig-zag fashion - no it does not.
Cracking is only at grout lines, in a straight line, far apart (13' or more). Only one cracked tile where the tile was saw cut for the patio door jamb.
There is a 3/16" gap between the tile and the baseboard at the exterior wall, but this narrows down to no gap at all where the floor edge is at the patio door. (Could the stem wall be actually displaced outward except at the patio door where the stem wall may have been terminated?)
Crack width about hairline to 3/32" elsewhere, only slightly tented in one location.
Not sure what type soil at my house, but I do know this was all formerly agricultural fields. There is some potential for soil swelling/collapsing due to moisture level, but this varies per exact location. I looked at a report for some other location:
Stiff sandy clay inter-bedded with loose to dense silty to clayey sand and sandy silt. Soil plasticity varies, low/non-plastic to low-medium. Potential for soil compressibility varies from low to moderate (1.0 to 5.5%). Potential for Soil Expansion moderately low.
RE: Concrete shrinkage
Cracks in gypsum wallboard. Everyone (realtors, public in general) seems to think they are due to structure settling - yes, that is true at my house in one location, but I think most are due to some sort of wallboard shrinkage (and most cracks are straight, at the tape lines) - any thoughts?
RE: Concrete shrinkage
RE: Concrete shrinkage
Drywall cracks are commonly caused by material shrinkage after the house is dried in and the AC starts to take the construction moisture out of the materials. Common at corners and re-entrant corners like door openings.