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Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec

Post Number: 274
Registered: 05-2003
Posted on Thursday, November 09, 2006 - 01:17 pm:   Edit PostDelete PostPrint Post

We specified slate to meet abrasion resistance requirements of ASTM C629 and MIA's Dimension Stone Design Manual Chapter 10, which both recommend an index value of 10 for commercial traffic floors, but will accept 8 as a minimum. The slate supplier is saying they can only provide 6.5. Any slate experts in the audience?
Richard Howard, AIA CSI CCS
Senior Member
Username: rick_howard

Post Number: 99
Registered: 07-2003
Posted on Thursday, November 09, 2006 - 03:32 pm:   Edit PostDelete PostPrint Post

It is hard to know what a stone's abrasion resistance number really means. There are a couple of things happening with the testing that could cause the lower Ha numbers for slate. In one instance, the testing per ASTM C 241 is yielding lower Ha numbers than when the test was originally developed due to a change in the standard abrasive. A second test method is now used for some suppliers, ASTM C 1353, that uses a Taber Abraser to give an Iw number (index of abrasive resistance). With that knowledge, perhaps you can get someone to explain where they are coming from, so far as how they come up with a hardness of 6.5 and how it compares with the old C 241's 8.0 that served as the historical hardness standard used in ASTM C 629.
I have always used the Burlington (UK) slate for flooring. Its hardness is higher than the domestic Virginia slates. They claim to have a hardness of 13 or better.
Maybe you could get a couple of samples and do your own testing comparisons.
Dale Roberts CSI, CDT
Senior Member
Username: dale_roberts_csi

Post Number: 15
Registered: 10-2005
Posted on Friday, November 10, 2006 - 09:57 am:   Edit PostDelete PostPrint Post

I work for a manufacture of installation materials for Tile and Stone. As you are probably aware slate is one of the softer stones, if you can use soft in the same sentence as stone. If the slate can take a polish or a hone it is one of the harder slates, and should be ok. There are also some quartzite’s that some people consider slates that may work for you. You may want to check with a couple of different distributors of stone. I can supply you with a couple of reliable distributors if you will Email me (dalero@cbpmail.com). I enjoy this forum and do not want to jeopardize it by listing distributors. If you are limited to this color of slate and it is relatively smooth slate with out to much clefting. It may be ok depending on the usage are we talking heavy usage (casino, mall) or light (small office building)? By the way I am writing this from Stone Expo 2006 convention in Las Vegas.

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