MidwestSE
Structural
- May 30, 2014
- 49
Hi everyone,
Here's what's going on:
-Recently constructed 6" thick SOG in a secondary containment facility (aka water tight concrete)
-Reinforced with 0.006Ag (heavy - I know) reinforcing per ACI 360 so that movement joints aren't required (they're expensive to install and maintain - extra steel is more expensive up front, but cheaper in the long run)
-We were just informed there is a lot of cracking, and we got pictures of some unusually large, long, and wide cracks. There doesn't appear to be a consistent pattern. E.g. one of the cracks looks like it's 15'-20' long at a re-entrant corner (that crack should have roughly 20 bars crossing it)
Notes:
-I've done this design numerous times before, and never had any issues like this
-I was informed they pond cured the concrete (this shouldn't harm the sog if done correctly?)
Prelim conclusions:
-It seems like it could be some sort of combination of the following items:
1. rebar wasn't placed properly on chairs prior to the pour, bars settled to the bottom in a few spots, and cracks occurred
2. concrete wasn't cured properly and plastic shrinkage resulted (water wasn't ponded up soon enough?)
3. could it have been issues with the mix design?
We have other areas on site with similarly reinforced slabs that aren't exhibiting any problems. Does anybody have thoughts or experiences similar to this?
Here's what's going on:
-Recently constructed 6" thick SOG in a secondary containment facility (aka water tight concrete)
-Reinforced with 0.006Ag (heavy - I know) reinforcing per ACI 360 so that movement joints aren't required (they're expensive to install and maintain - extra steel is more expensive up front, but cheaper in the long run)
-We were just informed there is a lot of cracking, and we got pictures of some unusually large, long, and wide cracks. There doesn't appear to be a consistent pattern. E.g. one of the cracks looks like it's 15'-20' long at a re-entrant corner (that crack should have roughly 20 bars crossing it)
Notes:
-I've done this design numerous times before, and never had any issues like this
-I was informed they pond cured the concrete (this shouldn't harm the sog if done correctly?)
Prelim conclusions:
-It seems like it could be some sort of combination of the following items:
1. rebar wasn't placed properly on chairs prior to the pour, bars settled to the bottom in a few spots, and cracks occurred
2. concrete wasn't cured properly and plastic shrinkage resulted (water wasn't ponded up soon enough?)
3. could it have been issues with the mix design?
We have other areas on site with similarly reinforced slabs that aren't exhibiting any problems. Does anybody have thoughts or experiences similar to this?
