Making concrete cylinders for testing 3

[psustruct]

I am a structural engineer and a new P.E. My boss has asked me to inspect one of our concrete jobs. So I went out and made test cylinders and did a slump test, along with my other duties.

Well, the contractor came over to me and asked me if I had a certificate that allows me to make the cylinders. I said no. Then he proceeded to scream at me.

I didn't realize that I needed a certificate. Does my degree and PE license surpass a certificate for making concrete cylinders?

 

[hokie66]

I don't think so. If you work for the concrete supplier or testing agency, then you would know. If you work for a structural consulting firm, making cylinders yourself is a strange thing to do.

 

[psustruct]

I do work for a structural consulting firm and yes, we make cylinders ourselves alllllll the time.

I'm being trained to do inspections... so this is all new to me. I don't know what I need certifications to do. My training is very nonchalant.

 

[Ron]

psustruct....assuming you are in the US, many specification require that concrete sampling be done by an ACI Level 1 certified technician.

Have you been properly trained to sample concrete and perform an appropriate slump test? Did you read the appropriate sampling and testing standards prior to performing the sampling and testing?

I've seen many, many PE's who didn't have a clue how to properly sample and test concrete...which makes the results of any subsequent testing questionable.

The contractor likely had two motives for doing what he did...one correct, one not so correct....

He was correct if his specification required a certified technician.

Otherwise, he was just trying to intimidate a young engineer (grizzled superintendents just love to do that!)by blowing smoke. You'll have to deal with that and the best way is to know more than he knows (which in this case you didn't, since you think the PE trumps all else!).

A little advice....when you go on a jobsite, there are a few things you need to know...

1. Learn from the older guys but also learn to filter the BS from the experience. Some of these guys have lots to offer...others have 1 year of experience repeated 20 times instead of 20 years of experience.

2. Don't think that a PE license gives you any insight into construction, other than the obvious design aspects and some materials science exposure that others don't have.

3. Don't come across on a construction site as a "college boy know-it-all"...it won't get you anywhere.

4. Do your homework and know more about your task than anyone else on the site. Also know the "why" not just the "how".

Good luck.

One big question...why were you sampling concrete rather than a certified testing lab?...assuming you work for a structural firm as you implied.

 

[hokie66]

Any other consultants do their own testing? I've been in the game all my life, and haven't made a cylinder since college days. I would have thought a PE inspecting concrete placement would make better use of time inspecting the reinforcement, making sure it stays where intended, and checking that a technician is monitoring the delivered concrete.

 

[Ron]

The other replies came in while I was typing my first reply, so now I know that you work for a structural firm but do your own sampling. Do you do your own curing and compressive strength testing as well? If not, then the results don't mean much.

For example, if you do the sampling and take the cylinders to a testing lab for testing, their report will state something like "concrete sampled by others" and then there will be a fine print caveat that states that they are not responsible for the results of concrete sampled by others.

Apparently, since you were not aware of certification programs for technicians, I would venture a guess that you have not been properly trained to sample and test concrete. If so, you need to get appropriate training and your firm needs to re-think its position on sampling and testing. That's unusual for a structural firm to take on that task.

 

[Ron]

hokie66...I agree. I've sampled and tested thousands of cylinders but that's because I spent over 20 years in the testing business in addition to the structural stuff. I don't recall ever having a structural design firm do any sampling or testing.

I've also been an ACI trainer and examiner...don't recall ever having a design structural engineer in any of my classes.

 

[psustruct]

Ron and Hokie, thanks for your replies.

I just want to say that I in no way think that a PE trumps all. But that is what a senior engineer at my office told me when I told him what happened on the job site today.

Also, when I get to the jobsite, I am upfront with the superintendent (and anyone else there) that I am new to inspecting and that I haven't spent much time on the jobsite. I have been trained by an older coworker on what to inspect, and I was just following his instructions by making the cylinders. I also inspect the reinforcement and placing.

Ron- Yes, I do take the cylinders to a testing facility. My firm does not cure the concrete or test the cylinders.

But thank you for your input. I'm not sure what I should do from here. I know my firm will expect me to make cylinders in the future.

 

[DWHA]

It all depends on what the job specific specs say. When I was summer help at the DOT, one of my job duties was to cast cylinders and beams (then later break the beams or deliver the cylinders to the lab). This was perfectly acceptable because the DOT spec did not require inhouse employees to be ACI certified.

Another year I was summer help at a consulting firm. I did hundereds of air tests and cylinders without ACI cert (this was on bridges, roads and foundations). The spec did not state that the cert was required for the job.

The only time anyone said anything to me was during a bridge pour, the RE on the project said that when I was rodding the conc for an air test, I rodded it 21 times not 20.

My advice is to put in a request to your supervisor to become ACI certified, explain what happened, and let him make the decision.

 

[nuche1973]

I agree with Ron. You should get certified if you plan on making cylinders. I also worked for a testing lab and am certified in both concrete strength and field testing. There's alot more to it than just making cylinders. When I was in a consulting firm we had a series of break results that were inconsistant. Since it was a large concrete project and these results were for the foundation, we decided to go out and take core samples. As we were sampling I observed the field tech make some cylinders. It was obvious he didn't know what he was doing. And when we inspected the samples in the curing room made by this guy were pitted and in poor condidtion. The cores broke at the specified strength. This guy was working as a summer intern for the lab and they were over booked. He wasn't certified, either. I guess thankfully, the summer was nearly over and he was leaving. Unfortuneately the lab had to core all the locations he sampled and check the results.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[Ron]

psustruct...another piece of advice....

Don't offer up your lack of experience on a jobsite. Get appropriate training, go onto the site with confidence and only get into a discussion on experience if challenged so.

As DWHA pointed out, get certified. It is not difficult and will give you paper credibility. Check with your local ACI chapter for the certification process...many chapters offer the courses.

Uh, DWHA....that would be 25 times per layer!

 

[psustruct]

I just looked at the specs for this job. They refer to ASTM C-31. So I looked up ASTM C-31, and it states, "The field technicians making and curing specimens for acceptance testing shall be certified ACI Field Testing Technicians, Grade I or equivalent. Equivalent personel certification programs shall include both written and performance examinations, as outlined in ACI CP-1."

This is a learning experience for me and I know that I am being thrown into this situation without enough training. I showed my boss the spec and he said, "So, we've been making cylinders for 16 years and we weren't supposed to be?"

Yep.

 

[nuche1973]

psustruct:
" he said, "So, we've been making cylinders for 16 years and we weren't supposed to be?" " Statements like that are time bombs when large projects are forced into litigation. Take the advise from Ron: get certified.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[psustruct]

There is a certification test in Maryland in 2 weeks. I told my boss about it in hopes that he would send me and my other coworker who does alot of inspection work.

It's never good when someone's answer is, "Because that's how we've been doing it for _____ years!!!"

 

[concretemasonry]

pstruct -

I hope the class goes into the variables that go into altering the appartent results from the tesing company. By making your own cylinders, you lose the link/chain of reliability and responsibility. After making the cylinders, the myriad of variables are the job site curing, handling, transportation that seem to lead to major structural questions reflecting back to the cylinders.

In our college concrete class(5 year curriculum thankfully), we had a twice a week lab session where mixes were made to measure the variables in mix design as per ASTM testing procedures. In addition, parallel samples were taken for testing with other variables included(rodding techniques, bumping samples during the cylinders in the first day of site curing, short site curing variables, bumping early samples and even transporting samples in a pick-up for a one mile trip and then tipping cylinders over before capping testing). This was a great educational eye-opener and the professor looked the other way when the high jinx, such as rodding in sugar, inserting rebars and freezing, etc. He drew the line at adding sugar to the mix since it had variable batch results that skewed both the real research and the "game" samples.

Because we were students we had the luxury of learning and not just cracking out samples and reports.

Just because a cylinder is made, that does not make it an absolute fact.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[dik]

I've done a lot of small projects in the 'boonies' and have taken my own cylinders... strictly 'unofficial', but better than nothing...

Dik

 

[BigH]

As Ron knows I am an "older" guy from Canada. When I was getting our laboratory CSA (Canadian Standard Association) certified bac in the 1970s, the technicians had to be certified by CSA for cylinders, slump and air but a Professional Engineer did not. I was told by the CSA rep that they would expect a Professional Engineer to be able to read and do what is expected or else not do it. As C-31 states, field "technicians" must be certified etc. but it does not state that Professional Engineers must be certified. I am not sure, anymore, if this is the case in the States or not - or even in Canada as I have been out for nearly 20 years.

With respect to levels of responsibility. Some have pointed out that since one firm has done the casting and a different one does the curing and breaking, the latter would rightly state that they had nothing to do with the casting of the cylinders. But on the other hand, cylinders are cast only to prove that the concrete has the "potential" strength as stated for the mix design - it in no way shape or form guarantees that the concrete in the structure has the strength. As others have hinted, the actual (not potential) concrete strength in the structure is dependent on curing, vibration techniques, segregation, climatic conditions and the like. This is a contractor attribution; so who is to blame?

In the end, the cylinders are only a measure to prove that the concrete can achieve - it is no guarantee; and when the strengths come out low, all suspect the concrete and those casting and breaking and very few suspect the lack of curing, lack of consolidation, and other contractor attributables. I had a chart one time (which if my grey cells permit me to remember I will try to find) that shows how much effect specific casting and constrution techniques can have on the strength of concrete.

 

[Ron]

BigH...excellent points.

Contractors these days, due to liability, are much less inclined to read/interpret the intent of specifications as to read the "letter" of the specifications. In that context, the additional "certification" is necessary.