Post Number: 11
|Posted on Wednesday, November 20, 2002 - 10:53 am: |
I have exterior walls that need to be rated at 2-hours. There is no U.L. listing for the exact wall assembly being used but the code official has agreed that by filling the cores of a 4" cmu veneer block with loose, expanded dry slag, water repellent vermiculite or burned clay or shale per Comm 51.045.1-r he will accept that as a 2-hour rating.
What's the best choice? I've been told not to use vermiculite since vermiculite has been linked to asbestos.
Post Number: 24
|Posted on Wednesday, November 20, 2002 - 11:03 am: |
Check the ICBO book for equivalents. ICBO has a list of assemblies they accept, and a 4" block wall may be on that list and your code official may accept the equivalent. I recall that this list of equivalents was adopted as part of the new International Building Code and may be acceptable from that perspective.
Regarding asbestos in vermiculite, the WR Grace mine in Libby Montana had a relatively high asbestos content and was why Grace reformulated their Monokote fireproofing product in the late 1980's. They now use shredded plastic beads for the light weight aggregate, but that is another story.
Most of the sources now available (including from Grace) are in Virginia and the Carolinas, and have no, or extremely low, asbestos content. I am not familiar with water repellent vermiculite. If you need more information let me know.
Post Number: 12
|Posted on Wednesday, November 20, 2002 - 12:38 pm: |
I can't find the ICBO list of assemblies on their web site - I'm probably not asking the right question. I have found reference to using perlite in lieu of vermiculite, though. If we used vermiculite, couldn't we just say "asbestos-free"? I'm guessing that the water repellent vermiculite is treated or coated, because vermiculite is water absorbing. The perlite is silicone treated.
|Posted on Wednesday, November 20, 2002 - 01:03 pm: |
Lynn, A good source of information on concrete block is the National Concrete Masonry Association. There are other acceptable fill materials for fire-rated block. Check out NCMA TEK 7-1A (www.ncma.org) for methods of calculating fire resistance of concrete masonry assemblies.
Post Number: 13
|Posted on Wednesday, November 20, 2002 - 01:41 pm: |
Thank you for all the help! I think that I've got the information I need to give to my architect. I knew I could count on you guys!