DIRTyEngineer
Geotechnical
Do you see many companies using the smaller cylinders ?
Does this met ASTM C-39 ?
Does this met ASTM C-39 ?
Eng-Tips is the largest engineering community on the Internet
Intelligent Work Forums for Engineering Professionals
-
Congratulations waross on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
4" by 8" cylinders
- Thread starter DIRTyEngineer
- Start date
- Status
I've used the small cylinders before for mixes with smaller nominal aggregate size (but the real reason was that our contractor (remote area of Laos) ran out of the big ones and wanted to use small ones. ASTM C470 indicates mould diameters ranging from 2 inches to 18 inches. However, under ASTM C31, section 6.1 indicates that the cylinder should be at least 3 times the nominal maximum size of the coarse aggregate. Further, the specification indicates that for acceptance testing only 6 inch and 4 inch cylinders are permitted (the latter when specified). I have spoken with our company's gurum in concrete in the past when dealing with a project in SE Asia and he was quite happy to go to the smaller cylinders for our nominal aggregate size of 25 mm.
They are being used in many parts of the country (USA).
The latest version of C 31 allows for use of 4 x 8 inch cylinders in lieu of 6 x 12 inch cylinders when job specs permit their use. However, since the version of ASTM C 31 recognized by the IBC does not permit for the use of 4 x 8 in cylinders as a standard specimen size, it is prudent to sell the idea to the building dept and EOR before using them.
There are several structural engineering associations currently evaluating the use of 4 x 8 in cylinders in lieu of standard 6 x 12 in cylinders. They will be relying on companion test results obtained from testing labs.
The latest version of C 31 allows for use of 4 x 8 inch cylinders in lieu of 6 x 12 inch cylinders when job specs permit their use. However, since the version of ASTM C 31 recognized by the IBC does not permit for the use of 4 x 8 in cylinders as a standard specimen size, it is prudent to sell the idea to the building dept and EOR before using them.
There are several structural engineering associations currently evaluating the use of 4 x 8 in cylinders in lieu of standard 6 x 12 in cylinders. They will be relying on companion test results obtained from testing labs.
![[wink]](/data/assets/smilies/wink.gif "[wink] [wink]")
BigH, chapter 35 of the latest IBC (2006) lists ACI 318-05 as a referenced standard. ACI 318-05 also has ASTM referenced standards for tests and specifications, many of which are listed in IBC-05.
What I find interesting, is that the IBC accepts most of the editions of the ASTM standards listed in ACI 318, but when it comes to ASTM C 31, it references the 98 edition, while ACI 318 references the 03 edition.
The 98 edition of C31, stipulates 6 x 12 in as the standard compressive strength specimen size (for acceptance testing for specified strength) but the 03 edition of C 31 stipulates the 6 x 12 inches and allows the 4 x 8 inches when specified.
Was the listing of C31-98 as a referenced standard in the IBC an oversight or deliberate; deliberate because committee members did not feel there was not enough data out there to justify the use of 4 x 8 inches to verify compliance with the specified compressive strength?
What I find interesting, is that the IBC accepts most of the editions of the ASTM standards listed in ACI 318, but when it comes to ASTM C 31, it references the 98 edition, while ACI 318 references the 03 edition.
The 98 edition of C31, stipulates 6 x 12 in as the standard compressive strength specimen size (for acceptance testing for specified strength) but the 03 edition of C 31 stipulates the 6 x 12 inches and allows the 4 x 8 inches when specified.
Was the listing of C31-98 as a referenced standard in the IBC an oversight or deliberate; deliberate because committee members did not feel there was not enough data out there to justify the use of 4 x 8 inches to verify compliance with the specified compressive strength?
DarthSoilsGuy
Geotechnical
in my experience, the concrete company QC's use the 4x8s for their internal QC and to defend against bad breaks from "independent CMT inferior testing methods". The concrete company QC bring 6x12s to the independent CMT lab when they are establishing a new mix design. We would only make a big deal about getting 4x8s permitted by the EOR if concrete would consistently be above 5ksi for large projects.
Even though concrete companies use the 4x8s, i don't think they would like 4x8s blanket approved for acceptance testing since the impact of a small flaw is magnified. Concrete companies have more lobbying power than CMTs too (read: all the power vs none).
off the subject,
i worked on a project where we were testing side by side with the concrete QC. The GC got test results from the concrete company and us separately. (Concrete QC doesn't usually distribute results until conflict) The EOR happened to see the results after a meeting in the trailer and compared with ours. The EOR asked the GC why the results would be consistently different, which they were. The GC passed this on to the concrete company that there was a consistent discrepency between the two. The QC at the concrete plant put together a letter to the owner & EOR trashing our technician's testing methods based on observations by the field QC for the concrete plant.
PUNCHLINE: Our breaks were consistently higher! Dumba$$
Even though concrete companies use the 4x8s, i don't think they would like 4x8s blanket approved for acceptance testing since the impact of a small flaw is magnified. Concrete companies have more lobbying power than CMTs too (read: all the power vs none).
off the subject,
i worked on a project where we were testing side by side with the concrete QC. The GC got test results from the concrete company and us separately. (Concrete QC doesn't usually distribute results until conflict) The EOR happened to see the results after a meeting in the trailer and compared with ours. The EOR asked the GC why the results would be consistently different, which they were. The GC passed this on to the concrete company that there was a consistent discrepency between the two. The QC at the concrete plant put together a letter to the owner & EOR trashing our technician's testing methods based on observations by the field QC for the concrete plant.
PUNCHLINE: Our breaks were consistently higher! Dumba$$
- Thread starter
- #7
DIRTyEngineer
Geotechnical
That is good for a laugh DarthSoilsGuy.
I have been down that road before.
We like to use the 4 X 8 's but half the time we don't get the spec until the job is half over or there is a problem.
I have been down that road before.
We like to use the 4 X 8 's but half the time we don't get the spec until the job is half over or there is a problem.
I did a bit of research into this issue and found out that:
1. Chapter 35 of the 2007 supplement to the 2006 IBC references C31-03a. As pointed out earlier, unlike earlier editions of C31, this edition of C 31 allows for 4 x 8 in cylinders when specified.
2. Proposed Changes to 2005 ACI 318... will permit for either 6 x 12 in or 4 x 8 in cylindrical compressive strength specimens...and there'll be no language like "when specified" in the case of the 4 x 8 in specimens. The wording of the revised Sec 5.6.2.4 reads as follows " A strength test shall be the average of the strengths of at least two 6 by 12 in cylinders or at least three 4 by 8 in cylinders made from the same sample of concrete and tested at 28 days or at test age designated for determination of f'c".
The 4 x 8 in cylinders will make life much easier for folks who do not like lifting 30 lb 6 x 12 in concrete specimens. And C 31-03 does permit internal vibration in lieu of rodding when consolidating specimens. How much easier can it get for concrete field technicians? They certainly need a break.
1. Chapter 35 of the 2007 supplement to the 2006 IBC references C31-03a. As pointed out earlier, unlike earlier editions of C31, this edition of C 31 allows for 4 x 8 in cylinders when specified.
2. Proposed Changes to 2005 ACI 318... will permit for either 6 x 12 in or 4 x 8 in cylindrical compressive strength specimens...and there'll be no language like "when specified" in the case of the 4 x 8 in specimens. The wording of the revised Sec 5.6.2.4 reads as follows " A strength test shall be the average of the strengths of at least two 6 by 12 in cylinders or at least three 4 by 8 in cylinders made from the same sample of concrete and tested at 28 days or at test age designated for determination of f'c".
The 4 x 8 in cylinders will make life much easier for folks who do not like lifting 30 lb 6 x 12 in concrete specimens. And C 31-03 does permit internal vibration in lieu of rodding when consolidating specimens. How much easier can it get for concrete field technicians? They certainly need a break.
Seattle allows the use of 4x8's for virtually all sampling and testing. This it to include mixes over 8K. We have found that 4x8's provide acceptable results, and have even been found to provide more consistent results. We noticed that 6x12's sometimes disappeared, were 'damaged' on site, not to mention during transport. Having the smaller size made it easier to transport, protect, and hide!
boffintech
Civil/Environmental
DarthSoilsGuy (Geotechnical) wrote, "PUNCHLINE: Our breaks were consistently higher! Dumba$$"
Maybe I'm the dumb-ass because I do not get, and frankly will never get, what the heck one set of test results being "higher" than a companion set of test results has to do with anything.
We still don't know if your test results were actually ACCURATE. It's entirely possible, and plausible, that both sets of tests were equally inaccurate!
Maybe I'm the dumb-ass because I do not get, and frankly will never get, what the heck one set of test results being "higher" than a companion set of test results has to do with anything.
We still don't know if your test results were actually ACCURATE. It's entirely possible, and plausible, that both sets of tests were equally inaccurate!
DarthSoilsGuy
Geotechnical
boffin,
it's a lot more than one set of cylinders. it was a consistent common difference throughout the project. the story sounds fun, but it wasn't at the time. we internally investigated our own operations and found nothing. the only thing that makes sense is that the concrete company's break machine was off and low. The point of that story is to show how knee-jerk the "blame the ITL" reaction is at the concrete plant, even when there isn't a problem.
i don't believe you would have reacted the same as the concrete QC manager, so i don't accept your claim to potential dumb-assness.
it's a lot more than one set of cylinders. it was a consistent common difference throughout the project. the story sounds fun, but it wasn't at the time. we internally investigated our own operations and found nothing. the only thing that makes sense is that the concrete company's break machine was off and low. The point of that story is to show how knee-jerk the "blame the ITL" reaction is at the concrete plant, even when there isn't a problem.
i don't believe you would have reacted the same as the concrete QC manager, so i don't accept your claim to potential dumb-assness.
dirtsqueezer
Geotechnical
Darthsoilsguy,
With that concrete QC discrepancy. I've never had a conflict like that with another agency and never want to, but I live in Seattle, and a big factor in our compressive strength is temperature of the cure. It gets so cold here in the wintertime that even our cure boxes don't insulate things properly, and this affects our breaks, especially on the high-early or PT.
It seems like to me there must have been other factors. Probably a dead issue by now, but that type of thing still sets me off. Find the problem and fix it, don't have blaming the other guy your first mode of action.
It could have been awhile before their load cell was calibrated, or your load cell was calibrated, pads were changed, ect. They could have forgone a cure box, or left it out in the sun (I'm pretty sure some of ours do). Results for the same concrete will differ even from cylinder to cylinder of the same mud, but to me methods of making them are pretty much foolproof, especially when there's someone watching over your shoulder. Water under the bridge, but that water's comin' from somewhere...
With that concrete QC discrepancy. I've never had a conflict like that with another agency and never want to, but I live in Seattle, and a big factor in our compressive strength is temperature of the cure. It gets so cold here in the wintertime that even our cure boxes don't insulate things properly, and this affects our breaks, especially on the high-early or PT.
It seems like to me there must have been other factors. Probably a dead issue by now, but that type of thing still sets me off. Find the problem and fix it, don't have blaming the other guy your first mode of action.
It could have been awhile before their load cell was calibrated, or your load cell was calibrated, pads were changed, ect. They could have forgone a cure box, or left it out in the sun (I'm pretty sure some of ours do). Results for the same concrete will differ even from cylinder to cylinder of the same mud, but to me methods of making them are pretty much foolproof, especially when there's someone watching over your shoulder. Water under the bridge, but that water's comin' from somewhere...
DarthSoilsGuy
Geotechnical
That's it. i'm calling the joke police to report a misdemeanor assault on my anecdotal story.
"but that type of thing still sets me off. Find the problem and fix it, don't have blaming the other guy your first mode of action."
--Would you be talking about the Concrete Company QC for writing the letter, the ITL who refers to them as dumbasses?
ironically, your point is same as the moral of the story i was telling, right.
as i've said before, it was investigated thoroughly on our side. People will just have to trust me on that. how else would i have been able meet this statement "the only thing that makes sense is that the concrete company's break machine was off and low."?
---------------
OK, now after you've accepted that there wasn't a consistent common error made by our lab/field testing method to give falsely high breaks.
The punchline to this story is that:
1. the letter issued by the concrete company observed ways our samples were incorrectly made.
2. our breaks were higher than theirs.
3. [speculation] the concrete company did not check to see what was going on before they wrote it, and probably thought the ITL breaks were lower (because that's how that letter read)
"but that type of thing still sets me off. Find the problem and fix it, don't have blaming the other guy your first mode of action."
--Would you be talking about the Concrete Company QC for writing the letter, the ITL who refers to them as dumbasses?
ironically, your point is same as the moral of the story i was telling, right.
as i've said before, it was investigated thoroughly on our side. People will just have to trust me on that. how else would i have been able meet this statement "the only thing that makes sense is that the concrete company's break machine was off and low."?
---------------
OK, now after you've accepted that there wasn't a consistent common error made by our lab/field testing method to give falsely high breaks.
The punchline to this story is that:
1. the letter issued by the concrete company observed ways our samples were incorrectly made.
2. our breaks were higher than theirs.
3. [speculation] the concrete company did not check to see what was going on before they wrote it, and probably thought the ITL breaks were lower (because that's how that letter read)
don't get me started on the supplier versus testing firm...(see my other thread). hey, if it blows up, instead of the supplier making companion cylinders some where else, have both the supplier and testing firm make extra companion cylinders (same size specimens). store the extras with the other guy's specimens. have each break their sets as usual and send the extras to the other's place for breaking (both parties do this). the suppliers specimens should break the same and the testing firm's should break the same regardless of where they are broken. if you want to rule out someone dropping them in route, deliver the darn things to each other's place of work. take it one step farther, be present at the other guy's place when the specimens are broken.
concretemasonry
Structural
msugco -
You are living in an idealistic land when it comes to testing concrete cylinders.
Cylinder testing is a low profit, variable volume testing process for local laboratories that helps them keep in contact with engineers, contractors and suppliers. Because of the variable volume, much of the actual preparation of samples and testing during the period of heavy construction activity is done by "grunts" with little real training. This even applies to certified laboratories because of the cyclical nature of construction.
ASTM standards represent the most responsible authority when it comes to standards and procedures. It is unfortunate that we have to deal with making the older standards and codes fit into the construction process while trying to retain a professional level of design and construction. This is in spite of the slow and tedious process of getting new findings, materials and procedures adopted by code authorities that really have little effect.
The idea of having parallel studies (size vs. aggregate) is not reponsible unless there is absolute long term uniformity of sample preparation, identical curing conditions, sample preparation by the same personnel, testing in the same facility with the same personnel and using the same testing equipment. This step has a major effect on the design and construction of all new structures.
Despite the the controls on the rate of loading (adjusted for sample size), larger testing machines with more rigid frames will provide higher and more consistant results.
In the past, independent laboratories provided the most accurate results compared to local suppliers results. With the advent of vertical integration of the concrete industry, supplier laboratories have surpassed many independent labs because of the international interest in research, quality control and local involvement. The days of "mom and pop" concrete plants are gone and the muscle of the the big four (or five) cement companies are concentrated on bringing the level of concrete oriented products up to the level of other advanced construction technologies.
You are living in an idealistic land when it comes to testing concrete cylinders.
Cylinder testing is a low profit, variable volume testing process for local laboratories that helps them keep in contact with engineers, contractors and suppliers. Because of the variable volume, much of the actual preparation of samples and testing during the period of heavy construction activity is done by "grunts" with little real training. This even applies to certified laboratories because of the cyclical nature of construction.
ASTM standards represent the most responsible authority when it comes to standards and procedures. It is unfortunate that we have to deal with making the older standards and codes fit into the construction process while trying to retain a professional level of design and construction. This is in spite of the slow and tedious process of getting new findings, materials and procedures adopted by code authorities that really have little effect.
The idea of having parallel studies (size vs. aggregate) is not reponsible unless there is absolute long term uniformity of sample preparation, identical curing conditions, sample preparation by the same personnel, testing in the same facility with the same personnel and using the same testing equipment. This step has a major effect on the design and construction of all new structures.
Despite the the controls on the rate of loading (adjusted for sample size), larger testing machines with more rigid frames will provide higher and more consistant results.
In the past, independent laboratories provided the most accurate results compared to local suppliers results. With the advent of vertical integration of the concrete industry, supplier laboratories have surpassed many independent labs because of the international interest in research, quality control and local involvement. The days of "mom and pop" concrete plants are gone and the muscle of the the big four (or five) cement companies are concentrated on bringing the level of concrete oriented products up to the level of other advanced construction technologies.
to the contrary, i understand that cylinder testing is not perfect and is variable from batch to batch, sample to sample, etc. over the long term of a project, the data should be trending though...and that is what should be looked at. cylinders don't mean jack when it comes to what's actually in place but they're a good place to start...plus, the industry has set them as the standard so we're stuck with it. what kills me is that the suppliers i have dealt with 100% of the time fall back to "kick the testing guy" because a break came up 100psi...GIVE ME A BREAK! if 29 out of 30 come up 100 psi low, it's probably a problem with the mix or the contractor is taking too long to place it. by no means is the building going to fall down but the owners and architects will want a credit for that 100psi they didn't get. i always try to remind architects of aci's low break acceptance criteria just to keep from getting in to it over a hundred psi...but some people see the cylinder as being the rosetta stone of how strong the building is...
re-reading through the thread, maybe i see where concretemasonry thinks i'm living in an idealistic world since i wasn't clear. when i said the supplier's and testing lab's cylinder should bread the same, i'm referencing more within the range of variability. i eluded to this a little in my last post but thought i'd clarify. i don't actually expect the supplier's cylinder to break at 3,200 and the lab's break at 3,200. the range of variability could be several hundred psi within the same set of cylinders. my main point was that i've seen folks point the finger at me because our cylinders broke 100psi less than the supplier's cylinder and tried to claim we were doing something wrong even though the trend for the job was very good. hope that makes my ramblings a little less confusing.
anyway, since ibc currently recognizes c31-03a and aci318-05 does too, how are you guys getting around using 4x8 cylinders? are you asking the engineer if they can be used on each and every job or are 4x8 cylinders typically included as acceptable on the plans in your area?
i suspect ibc may pick up c31-06 on the next round of supplements (which would then allow either size cylinder). anyone know when that date might be since i can't seem to find it? also, when might the aci changes go in to effect (since you'd have to make 3 instead of 2 28-day cylinders for the smaller size)?
i'll keep looking and post if i find the answer to my own question...
anyway, since ibc currently recognizes c31-03a and aci318-05 does too, how are you guys getting around using 4x8 cylinders? are you asking the engineer if they can be used on each and every job or are 4x8 cylinders typically included as acceptable on the plans in your area?
i suspect ibc may pick up c31-06 on the next round of supplements (which would then allow either size cylinder). anyone know when that date might be since i can't seem to find it? also, when might the aci changes go in to effect (since you'd have to make 3 instead of 2 28-day cylinders for the smaller size)?
i'll keep looking and post if i find the answer to my own question...
i see it is on the next round of revisions (icc agenda for the february meeting) to change 03a to 06.
i'm not sure when the change would actually be accepted as code though.
i'm not sure when the change would actually be accepted as code though.
well, i happened to run across march 10 as the date that the code changes will be posted (still not sure if that means immediate adoption by code or if there's some time after that...i would think immediate or almost immediate)
Does the new ASTM allow the use of 4*8's as opposed to 6*12" yet?? Have not heard anything about it. Read somewhere that you will have to make 2 4*8's for every 1 6*12. How much room is that actually going to save??Roughly 40%. Problem I feel w/ the smaller test samples is they are more prone to temperature varibles,fabrication process as well as damage.
How many times have cyls. been damaged due to an arguement with the contractor. As well as people using them for tables.When this comes into affect, plan to be doing alot of windsor probes as well as cores.
How many times have cyls. been damaged due to an arguement with the contractor. As well as people using them for tables.When this comes into affect, plan to be doing alot of windsor probes as well as cores.
- Status
Similar threads
- Locked
- Question
