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"Moisture Protection & Firestop Specialists"

Understanding ASTM C-920*

ASTM C-920 consists of a series of test methods designed to evaluate  elastomeric sealants intended for use in the construction industry. 

Once a sealant has been tested and found to perform within the allowable limits for each test, it is described as meeting ASTM C-920.  However, simply stating that a sealant meets C-920 is not acceptable.  Sealants qualifying under the specification are classified as to Type, Grade, Class and Use.  Correct representation of C-920 must include these classifications.

The Type, Grade, Class and Use are described as follows:

Type S - A single component sealant.

Type M - A multicomponent sealant.

Grade P -  A self-leveling (pourable) sealant.

Grade NS - A nonsag (gunnable) sealant.

Class 100/50 -  A sealant capable of 100% extension and 50% compression

Class 50 - A sealant capable of 50% extension and 50% compression.

Class 35 - A sealant capable of 35% extension and 35% compression.

Class 25 - A sealant capable of 25% extension and 25% compression.

Class 12 1/2 - A sealant capable of 12 1/2% extension and  12 1/2% compression.

Use T(1) -  A sealant designed for use in pedestrian & vehicular traffic areas. High Modulus, Firm sealant.

Use T(2) A sealant designed for use in pedestrian & vehicular traffic areas. Low Modulus, Soft sealant.

Use NT - A sealant designed for use in nontraffic areas.

Use I - A sealant designed for use in joints that are continuously immersed in a liquid.

Use M - A sealant that meets C-920 when tested on mortar.

Use G - A sealant that meets C-920 when tested on glass.

Use A - A sealant that meets C-920 when tested on clear anodized aluminum.

Use O - A sealant that meets C-920 when tested on substrates other than the standard glass, aluminum or mortar

* ASTM Volume 04.07 Oct. 2015



 
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