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Tom Peck
Senior Member
Username: tom_peck_csi

Post Number: 19
Registered: 08-2004
Posted on Thursday, September 22, 2005 - 10:45 am:   Edit PostDelete PostPrint Post

Regarding sealants, and ASTM C920:

Are the only Grades S (sag?), NS (non-sag), and P (?)?
Are the only classes 12 1/2, 25, 50, and 100?
Are the only uses T (traffic?), NT (non-traffic?), M, G, A, and O?
What do the letters and numbers refer to?

Thanks for your help.
Wayne Yancey
Senior Member
Username: wyancey

Post Number: 70
Registered: 05-2005
Posted on Thursday, September 22, 2005 - 11:59 am:   Edit PostDelete PostPrint Post

Type defines whether products are premixed or require mixing at the jobsite as follows:

Type S products are those furnished in prepackaged cartridges or other forms in which no jobsite mixing is required. The single-component products are more expensive than their multicomponent counterparts because of the extra labor and packaging costs involved in supplying materials in small quantities rather than in bulk form.

Type M products are those furnished in two or more parts for mixing at the jobsite. Multicomponent products include those with two components consisting of a base and a catalyst or with three components consisting of not only a base and catalyst but also a separate color component. Multicomponent products cure faster than their single-component counterparts, which is often advantageous for joints subject to traffic or similar exposures where this characteristic is desired. Despite concerns over poorer quality control by mixing products at the jobsite, the multicomponent products are often superior in quality of performance in comparison to corresponding single-component formulations.

Grade defines the flow characteristics of the sealant as follows:

Grade P products have sufficient flow to fill joints in horizontal surfaces and remain level and smooth at temperatures as low as 40 deg F (5 deg C). This designation generally applies to products rated for traffic use.

Grade NS products are suitable for installation in joints in vertical surfaces without sagging at temperatures between 40 and 122 deg F (5 and 50 deg C). This designation can apply to sealants classified for both traffic and nontraffic uses. They can be installed in traffic joints in sloping horizontal surfaces where a self-leveling type would flow downhill.

Class identifies sealants according to their tested capabilities to remain adhered to given joint substrates without experiencing cohesive failure when subjected to repeated cycles of joint expansion and contraction over a minimum range measured as a percentage of joint width at the time of sealant application.

Classes 12-1/2, 25, 35, 50, and 100/50 are the five designations in ASTM C 920 for rating movement capability. Although sealants ought to perform in the field as well as they do during testing, it is more prudent to design joints that impose lesser extremes of movement than that demonstrated in the laboratory because of the unknowns present in the field relative to qualities of joint preparation, sealant application, construction tolerances producing varying joint widths, and the effect of installation temperatures on joint widths. With the recognition of new Classes 35, 50, and 100/50, the sealant industry has finally acknowledged sealants with this higher movement capability after years of resistance by manufacturers who did not offer products with these extra movement capabilities.

Use T classifies sealants designed for joints in surfaces subject to pedestrian and vehicular traffic

Use classifications related to exposure are designated as follows:

Use NT classifies sealants designed for nontraffic exposures.

Use classifications related to joint substrates are designated as follows:

Uses M, G, and A refer to sealants that remain adhered, within given parameters, to various standard specimens including, respectively, mortar (M), glass (G), and aluminum (A) when tested for cyclic movement and adhesion-in-peel. It is important to understand that the specimens related to these designations are not those specified for the Project but those that comply with restrictive material specifications in the ASTM test methods. Mortar is always portland cement mortar, glass is clear float glass, and aluminum is clear anodized aluminum of a specific alloy. These standard substrates are covered in ASTM C 1375, Guide of Substrates Used in Testing Building Seals and Sealants.

Use O refers to substrate materials other than M, G, and A. Unless it is definitely known that the joint substrate materials for the Project are identical to the materials designated by M, G, and A, retain Use O.

The major change to ASTM C 920 was the recognition of sealants with higher movement capabilities by including Classes 35, 50, and 100/50 and adding Use I for sealants designed for use in joints that will be submerged continuously in liquids.
Tom Peck
Senior Member
Username: tom_peck_csi

Post Number: 20
Registered: 08-2004
Posted on Thursday, September 22, 2005 - 12:16 pm:   Edit PostDelete PostPrint Post


Wow, thank you for the summary/education!

Richard Baxter, AIA, CSI
Senior Member
Username: rbaxter

Post Number: 16
Registered: 12-2004
Posted on Thursday, September 22, 2005 - 03:07 pm:   Edit PostDelete PostPrint Post

I enjoyed that summary as well. Thanks Wayne.

I believe the 'P' in Grade P stand for 'pourable,' by the way.
David Axt, AIA, CCS, CSI
Senior Member
Username: david_axt

Post Number: 551
Registered: 03-2002
Posted on Thursday, September 22, 2005 - 04:39 pm:   Edit PostDelete PostPrint Post


P = Pourable
S = Single Component
M = Multiple Component
NS = Nonsag
T = Traffic
NT = Non Traffic

In addition to the uses (M, G, A, O) that Wayne explained there is I = Submersible in watter.
Sheldon Wolfe
Senior Member
Username: sheldon_wolfe

Post Number: 160
Registered: 01-2003
Posted on Thursday, September 22, 2005 - 05:36 pm:   Edit PostDelete PostPrint Post

It's expensive, but I recommend getting the ASTM Standards in Buildng Codes on CD. In the past I had the four-volume set, but it's so much faster to just type in an ASTM number and have it pop up on my monitor.

I learned a valuable lesson about reference standards my first couple of weeks as a specifier - know what's in them! Many reference standards contain a variety of types, grades, options, etc., so "comply with ASTM X" alone may not say much at all.
Tom Peck
Senior Member
Username: tom_peck_csi

Post Number: 21
Registered: 08-2004
Posted on Friday, September 23, 2005 - 09:47 am:   Edit PostDelete PostPrint Post

That would be a big investment, but probably a good one ... ranging from $1,700 to $4,500 depending on the scope of the documents for the Construction Collection, and whether this is a one time subscription or with updates; and there are still the Paints Collection, DOD Collection, etc. (And $8K to $21K for the complete set).

The ASTM website doesn't allow me to view the contents (and compare) the Construction Collection's Table of Contents.

Can someone comment on the adequacy of the set of ASTM standards in the 2003 IBC's companion book vs. the obtaining the entire set of the Construction Collection of ASTM standards?

Are the standards in the Paint Collection, or the Metals Collection, etc., included in the Construction Collection?
Wayne Yancey
Senior Member
Username: wyancey

Post Number: 72
Registered: 05-2005
Posted on Friday, September 23, 2005 - 10:59 am:   Edit PostDelete PostPrint Post


The ASTM Standards in Buildng Codes will not include all of the ASTM standards you may encounter in your work, but well worth the cost.

I second Sheldon's recommendation. We have the single volume hard copy.

Confession: Everything in my first posting is included in the evaluations for section 079200 of AIA Materspec. Evaluations are an excellent resource tool.
Anne Whitacre, CCS CSI
Senior Member
Username: awhitacre

Post Number: 246
Registered: 07-2002
Posted on Friday, September 23, 2005 - 11:50 am:   Edit PostDelete PostPrint Post

there is another option: we have a yearly subscription that allows us to download 50 ASTM standards a year. I copy them as needed, and keep in a file on the hard-drive. You may find that there are some ASTM standards that you use all the time and others that are somewhat more rarified in their application. We have the IBC companion book, and then use the subscription to augment those.
Anne Whitacre, CCS CSI
Senior Member
Username: awhitacre

Post Number: 247
Registered: 07-2002
Posted on Friday, September 23, 2005 - 04:13 pm:   Edit PostDelete PostPrint Post

I think it would be appropriate here to mention that all the information that Mr. Yancey quoted above came from a Masterspec Supporting Document for section 07920. These are copyrighted documents, and the source should be acknowledged.
J. Peter Jordan
Senior Member
Username: jpjordan

Post Number: 131
Registered: 05-2004
Posted on Monday, September 26, 2005 - 09:16 am:   Edit PostDelete PostPrint Post

I have used the "ASTM Standards in Building Codes" for more than 25 years. These volumes (now 4), includes ASTMs referenced by the major building code organiazation, US HUD, MasterSpec, BSD SpecLink, SpecText, USA Corps of Engineers, and USN NAVFAC.

I have occassionally purchased another spec from ASTM, but very rarely (maybe once a year on average). I purchase a new set every 3 or 4 years; although, I can make a case for occassionally purchasing "out of cycle" if I know there is a major update to a group (like what has happened to gypsum board).

I still find the premium for the CD version a little steep, but the hardcopy is well worth the cost.
Wayne Yancey
Senior Member
Username: wyancey

Post Number: 75
Registered: 05-2005
Posted on Monday, September 26, 2005 - 05:39 pm:   Edit PostDelete PostPrint Post


Please read my second posting above your first posting for my acknowledgement of AIA MasterSpec Evaluations as my source.

See my confession at bottom.


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