Assisted Slump Test

[IsenCam]

We have a situation where a concrete supplier brought their own QC onsite to test a recent slab. It was observed by us that the concrete finishing sub aided in the actual slump test with the QC tech from the supplier. The concrete finisher actually was the one who placed the concrete in the cone while the QC rodded the sample. While the placement of 3 equal layers and number of roddings wasn't acceptable, a comment was made by the QC tech that it was "common practice" for the concrete finisher to aid in a slump test. I have never had any help from a sub nor would I have asked. I can not ever recall this being mentioned in any of my ACI classes either. I was just curious if this is a "common practice"

 

[BigH]

Not in my days. But, then, again, in India and China, they use 5 guys to do a sand cone density test. You mentioned that the placement and rodding wasn't acceptable. Can you elaborate? I think that would be more a worry than if one guy was filling and one was rodding.

 

[IsenCam]

You are correct BigH, the filling and rodding are more important then the assistance being given by the sub on the job, but that was what caught me off guard more than the others. While attempting the slump test, the sub filled the cone in a continous motion, not really 3 layers, just one motion while the QC rodded the sample as it was being filled. I counted the rodding and the it varied from time to time on the sample. It was not a clear 3 layers, each layer rodded 25 times slump test. It was a hurry up and get this done so we can get to placing the concrete type slump test.

Thanks for the comment.

 

[BigH]

IsenCam - not acceptable. As soon as an inspector sees this, he should, in my view, go up and dump the cone upsidedown and get them to do it right. Now having said that, an inspector should be able, after a number of months on the job, to tell a 30, 50, 80mm slump to a reasonable degree. In lieu of the proper slump, this information is needed. But this doesn't justify if the pour is an important one. The best thing is that if the inspector sees the work being done poorly, then to get it done right. In this case, another slump, properly done, could have been immediately ordered. (I know, always easier to say after the fact that when you are right there on site with certain pressures.).

 

[IsenCam]

You are correct again BigH. We were onsite to "observe" unfortunately. I was not in a position to actually make a call on the situation, although I would have given the chance. The company I am currently with is just now realizing that not all concrete is the same. I am the only trained indivdual on staff with ACI certifications as well as extensive concrete training from an accredited engineering program. With just the experience I had with working as an tech for in an older job, I was able to identify the issues that were at hand. I think that I have brought some attention by others to the table now, so I hope it paid off.

 

[boffintech]

BTW, it's understood, I hope, that in the slump test it's three equal layers by volume. And contractors helping during tests is pure BS. If anything this kind of help is an impediment as this case clearly demonstrates.

BigH suggest that in this situation the inspector "should...go up and dump the cone upside-down and get them to do it right." While no one enjoys giving a contractor bad news more than myself, I would avoid this sort of in-your-face confrontation. The person(s) performing the tests should simply be notified that the test proceedure(s) do not meet the standard, that the results derived are completely erroneous, and that the facts of the matter will be delineated in a report to the owner or the other powers that be.

If any of the following documents were in the specs I'd say you have argument as these two clowns were obviously NOT qualified.

ACI-301
1.6.2 – Field tests of concrete required in 1.6.3 and 1.6.4 shall be made by an ACI Concrete Field Testing Technician Grade 1 in accordance with ACI CP1 or equivalent.

ASTM C-94
16.2 – Tests of concrete required to determine compliance with this specification shall be made by a certified ACI Concrete Field Testing Technician, Grade I or equivalent.

ACI-318
5.6.1 — Concrete shall be tested in accordance with the requirements of 5.6.2 through 5.6.5. Qualified field testing technicians shall perform tests on fresh concrete at the job site, prepare specimens required for curing under field conditions, prepare specimens required for testing in the laboratory, and record the temperature of the fresh concrete when preparing specimens for strength tests. Qualified laboratory technicians shall perform all required laboratory tests.

 

[BigH]

boffintech - guess I've worked in China,Laos and India too long! But, it is the idea that you shouldn't be complacent. But, of course, you don't need to be confrontational in the USofA.