Philosophical Question on Concrete Testing

[BigH]

A bit of a philosophical difference here on site . . . just throwing out a question if anyone wants to bite !

 

[BigH]

Oh . . . for mass concrete, what would your "failure criteria" be? To ACI, it is one failure in 20; for mass concrete?

 

[Ron]

BigH...you are correct...the primary reason for the testing is to test the mix design...not the in-place concrete. That concept is very hard to get across to some people. When dealing with a random distribution of test points, one change in many points doesn't statistically make any difference...besides, in the original random distribution it could have worked out that way anyway.

Actually once it leaves the discharge chute, it makes little difference where it goes as long as you document its location in the event of failure.

Mass concrete control has to be at least as great as conventional concrete, so even for the quantity, I would not reduce the failure criteria.

 

[emmgjld]

I agree with Ron on both counts.
I bet the discussion on-site will create interesting discussion, some of which will never go away.
I have a couple of similar issues which still crop up 32 years later.

 

[BigH]

Thanks guys . . . We had a visit from a very well known Brazilian concrete expert - has done over 30million m3 of mass concrete - he is of the opinion, for mass concrete, that you can and should reduce the failure criteria - from 1 in 20 to something like 1 in 5. His reasoning, as I understood it, was that even if small sections of the massive structure were a bit understrength, the overall performance of the structure is not changed. I tend to agree in that, too, with mass concrete, you can count on the continued increase in strength. Thanks, again, for the validation of the philosophy! Can I send you all a virtual ayam sate with nasi goreng?

 

[Ron]

BigH...sounds great! Not sure if beer goes with it, but will have one after! I think my wife (picky eater) would even like that.

The Brazilian makes a good point about the overall concrete performance, I'm just not so sure I would relax the failure criteria a lot, since it would then imply license to get sloppy.

 

[fattdad]

BigH: Late to the discussion, but I'm with you (well and others). It's a test of the batch plant, simple as that. It makes little difference where the concete is going. I know that you are taking cylinders for every 100 m3, but adding a few slumps for interim batchs is a good way to show uniformity also.

No comment on the Brazilian guy. I can see the discussion going either way. . .

f-d

¡papá gordo ain’t no madre flaca!