×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

4"x 8" Concrete Cylinders vs. 6"x12"
3

4"x 8" Concrete Cylinders vs. 6"x12"

4"x 8" Concrete Cylinders vs. 6"x12"

(OP)
A local material and inspection company has sent out a letter to the local engineers informing them that they will now be using 4" diameter x 8" tall concrete test cylinders as their standard concrete test cylinder, instead of the more traditional (at least around here) 6" x 12" cylinder.

The firm indicates this is now allowed by the most recent edition of ASTM C31.

The testing firm goes on to say that they realize their is some adjustment factor between the two cylinders, as the 4" x 8" cylinder will typically give a higher break strength, but that there is no nationally accepted value for this adjustment factor. However, they did some testing on their own, and are proposing to use a 5% adjustment.

Have other encountered this idea in your area? What are your thoughts on this? How do your local testing firms adjust between the two sizes of cylinders? Or do they adjust the results? Does it seem right to base the adjustment factor off of a relatively few (less than 50 ) locally performed tests that are not sanctioned by a major code or industry standard?

Just looking for thoughts on the issue. Thank you for any and all repsonses.

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

We've been using 4x8 cylinders in Canada for several years and you shouldn't have any concerns.  Test results (stress) are indistinguishable from 6x12.  They have an advantage of being smaller, lighter, easier to handle, less disruption in moving, smaller storage space and require smaller testing machines.  They also require less concrete and provide less aggregate/landfill... No downside.  Only thing is that with the 6x12 and 4x8 cylinders, the maximum aggregate size is dia/3 so the mix size is limited... cannot use 1-1/2 aggregate, but for 3/4" or 20mm OK.

Dik

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

2
There are numerous studies on the effect of MSA and specimen size on uniaxial compressive strength. We had discussed this a while back http://www.eng-tips.com/viewthread.cfm?qid=136149  

For acceptance testing for specified compressive strength, ASTM C 31-06, Section 6.1 does permit either 6 x 12 or 4 x 8 cylinders. This is a new provision....and a lot of labs like it, particularly their lab techs.

If projects are going to be based on the IBC-00, IBC-03, or IBC-06, the edition of ASTM C 31 in Chapter 35 -Referenced Standards, does not permit this. Also check section 3.8 of ACI 318, for the edition of ASTM C 31 permitted...and then refer to Sec 5.1 of C31. In C31-06, this section is now 6.1

All the same, an enforcing jurisdiction may decide to come up with regulations permitting the use of the smaller cylinders before ACI 318-08(??) references ASTM C 31-06. I'd check with them.

 

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

Henri2:
Are you saying that it's only referenced in C31-06 and they can only be used for codes referencing that document?

Dik

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

dik, for building departments that use the IBC, that should be the case, unless the enforcing agency grants pemission or does not enforce the code.

I am sure that in time, 4 x 8 cylinders will be used extensively out here.

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

Thanks Henri2... the only thing I noticed when the 4x8 cylinders were used, was that there was no reduction in the cost of doing them... a sneaky way not to implement an extra to contract...

Dik

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

dik, it's high time labs started making some easy money...LOL.

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

Our company, location NH, still uses the 6X12.  The reason being, we only have a psi machine for the 6X12, and would have to cap both ends of a 4X8, if we were to test it.  A machine does exist, and a chart also exists, for testing the 4X8, and calculating the total lbs, and total psi.

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

It is true that the code being enforced will refer to a specific version of a referenced standard (Chapter 35 of the IBC).  The codes being on a different cycle than standards, typically lag the standards.

However, the building official can accept, as provided in Chapter 1 of the IBC, as an accepted alternative, new revised standards like the newer referenced standards.  A conservative building official may require you to adjudicate a varience but should not oppose it.

Don Phillips
http://worthingtonengineering.com

RE: 4"x 8" Concrete Cylinders vs. 6"x12"

(OP)
All:

Thanks.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources