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