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