Difference between designers fc' and as-tested fc'
Difference between designers fc' and as-tested fc'
(OP)
You have done your calcs with 28-day conc. strength of say this much ksi. The building is put in place and later on tests on samples show a little deviation?
How much deviation is tolerable?
regs
IJR
How much deviation is tolerable?
regs
IJR





RE: Difference between designers fc' and as-tested fc'
If testing the "in-place" concrete by coring, the allowance is that if the core strength achieves 85 percent of the design strength, then it is generally acceptable for strength purposes.
RE: Difference between designers fc' and as-tested fc'
respects
IJR
RE: Difference between designers fc' and as-tested fc'
RE: Difference between designers fc' and as-tested fc'
And one day you will be invited to visit wherever I will be then. Just allow some time.
Keep up the good work Ron
regs
IJR
RE: Difference between designers fc' and as-tested fc'
This is where I think permissable stress design falls down, and where limit state (or LRFD, I think) comes into its element. Full statistical data can be made available from the supplier, you could then match this with your design strength characteristic curve - and usually it is okay(ish!)
Colin Caprani
RE: Difference between designers fc' and as-tested fc'
The answer to the original question by IJR requires some knowledge of the local suppliers, testers and the contractors. Full statistical information can be invaluable but, is often not availible or sometimes, believable. I think some consideration of the history of the local suppliers, testers and the contractors will be very important in the final decisions.
I say all this while being in the business and having worked hard to maintain good, competant personnel and a believable laboratory.
RE: Difference between designers fc' and as-tested fc'
The good news is that it is getting better, at least here in the States. Automated batching and computerization have significantly improved the POTENTIAL to acquire good data, and to be able to apply these data to evaluative purposes. Keep in mind that ready-mix suppliers rely on multiple laboratories for their data in the normal course of business. One must assume that data from multiple laboratories are comparable. Not always a good assumption.