is this an issue?
is this an issue?
(OP)
I'm checking concrete mix submitted by contractor. I don't really do this match. only thing not matching our notes is estimated density = 140pcf, not 150 pcf per our notes. any problem with this? f'c is met.






RE: is this an issue?
RE: is this an issue?
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: is this an issue?
Also keep an eye on Fly Ash percentage and AE. other than that durability may be an issue but only if it is rough/demanded use.
RE: is this an issue?
RE: is this an issue?
RE: is this an issue?
I had a slab once with high Fly-Ash placed in middle of winter. Cold weather curing used. and the slab ended with like 1000psi instead of 4000psi. The plant had record of the mix used and video of components being added so it isn't like someone forgot to hit the 'Cement' Button at the batch plant. Fly Ash took the blame and i have been conscious since, maybe incorrectly? You guys probably know better than I!
RE: is this an issue?
For unreinforced or concrete with minimal reinforcement, there are a couple of situations where the 150 pcf number is not conservative. If the dead weight of concrete is used to resist uplift, better to use its true weight (or less) of the concrete than 150 pcf. The same reasoning applies if the concrete is submerged or below the water table and is being used to resist floating - such as the seal of a cofferdam.
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: is this an issue?
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: is this an issue?
RE: is this an issue?
And batch plants now video tape their mixes? Wow...that sounds like yet another way to move towards putting the blame at the foot of the engineer. I specify f'c but I'm no chemist; I assume they know their mixes better than I do. But if they're providing something that comes in at 1,000 psi instead of 4,000 psi and then providing a videotape to play "gotcha!"...well, I'll think long and hard before I ever "approve" another mix design submittal. Surely they must have had some inkling that it would come in low? After all, that's their entire line of work.
RE: is this an issue?
RE: is this an issue?
This does not surprise me in the world that we live today...I know from experience that all telephone calls to the batch plant dispatcher of one of the largest concrete suppliers in Sydney (Australia) are recorded and time stamped, and a play back is often used to verify/deny customer vs dispatcher conversation.
RE: is this an issue?
I am intrigued by the phone conversations being recorded.
RE: is this an issue?
RE: is this an issue?
RE: is this an issue?
Lightweight concrete affects fire rating? Is that in the IBC or some place similar? I'd be interested to learn about it. In my experience lightweight concrete performs better in a fire. But then, that's with the view of looking towards the concrete itself, not as the structure as a whole.
Hokie66,
I can add an anecdote in support of what you said. As a very junior engineer I watched the tester rod the cylinders a total of 10 times vs. the 25 times required. I was too green to feel confident speaking up and sure enough, the concrete cylinders broke low. To check the concrete's strength we had to conduct Swiss Rebound Hammer testing or some other type of in-place testing which name I can't remember at the moment. It involved shooting powder actuated studs into the concrete and measuring how far they stuck out, if I'm remembering correctly.
RE: is this an issue?
RE: is this an issue?
Windsor Probe test.