huangyhg

early concrete loading
on our structural general notes page for our typical jobs, we usually put a note that says do not load concrete members before 14 days and before their specified 28 day strength is obtained. i have a contractor asking if he can load it before the 14 days. is there an aci document that i can reference to find a good answer for his request? aci 347? is there general industry practice for this?

probably not, but the earlier you load it the higher the creep deflection will tend to be.
just say no, they tendered for it as is with the notes stating that, if they didnt read the notes then thats their problem.
you can strip formwork earlier not sure about loading. we have loaded ground slabs earlier. but these were lightly loaded. can you carry out quick design check on the proposed loading, advise him of min strength, say he has to do cube tests to prove. that should put him off.
in seven days ordinary conc. should attain it's 75% of specified strength. contractor can load it to some percentage (say 25%) of it's full capacity so that construction can proceed. make sure to give this info in writing and make him responsible for any outcome of "his" deviation from standard procedure. also you should have 7 days test result available from same job.
when you write like this, probably he will like to wait ! ! !
another way to handle the situation is to tell the contractor something like this: "since you want to do something that is not allowed by the specs, you provide the documentation to support your request."
as an owner, we have used this many times solve this type problem. most of the time that is the end of the matter, but every now and then a contractor will come up with a way to do what he wants that is acceptable and benefits the project.
as someone who does a lot of construction engineering, in most cases it is the contractor's engineer who deals with situations like this, unless there are very specific concerns with the proposed situation. i would do as suggested by slideruleera and hand the responsibility back to the contractor.
i get asked this question quite often. my standard reply is that either a high early cement or an accelerator needs to be added to the mix. then a compression test on a three day cylinder should be made. after i have had the opportunity to review the results of the test break then i will decide if it is acceptable to begin loading the concrete.

__________________
借用达朗贝尔的名言：前进吧，你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]