Active Standard: C920 - 11
Proposed ballot to change C 920 to include a weathering test. Reason: The C 920 Specification for Elastomeric Joint Sealants covers sealants for all kinds of applications but predominantly outdoor applications. It makes no sense that this specification does not contain a weathering test that has movement similar to the movements in C 719. Since this specification is for sealants in moving joints the weathering test would need to show how weathering influences movement ability. We have an ASTM test C 1519 that does this. It is the best of the accelerated weathering test for sealants that is presently on the books. Earlier we recognized the need to put a weathering test in C920 and put the only official weathering test we had, C 793 (put sealants on an aluminum sheet and look at cracks (flat and after bending) after 250 hours in an accelerated weathering machine. It assumes all weathering applications are equally mild. Old window putty might pass this test as used in this specification. It was a placeholder test until we put a more realistic test in the specification. The sample is not a joint, the weathering time is totally insignificant, and it has no joint movement. The C1519 test is a relatively simple test method where standard C719 joints (Tensile Adhesion) are weathered for 4 weeks (672 h) then cycled 6 times at RT then inspected for adhesion or cohesion loss by C719 criteria. If the test specimens pass, then the joints repeat 4 week weathering and movement cycling until failure. I am proposing that we consider adding a weathering element that has weathering classes as a Use classification in C920. C1519 would be the test method used. My initial thought is 3 Weather Exposure Use classifications: Use IN: for use in interior or low weather exposure applications These sealants would pass a minimum of 2 weathering and movement cycle without failure Use EX: for use in typical exterior applications These sealants would pass a minimum of 6 weathering and movement cycles without failure Use HE: for use in high weather exposure applications These sealants would pass a minimum of 10 weathering and movement cycles without failure In each case, failure would be defined by meeting adhesion and cohesion loss criteria. The joint dimensions for cycling would be the same as is tested in C719 movement classes i.e., a sealant passing +/-50% by C719 must also pass +/- 50% by C1519 at the designated Weather Exposure Use Class. Conceivably a sealant could achieve a higher Weather Exposure Use class at a lower movement i.e. there could and probably would be sealants that would be a weather class HE and a movement class 12 . My argument for doing this is that C920 becomes less relevant as a specification if it does not include a meaningful weathering component to the standard. We now have a reasonable and simple test method to replace C793 and with it we can develop Use classes that have meaning. We need to move in this direction to keep our standards relevant. Thus I propose the we include C 1519 Standard Test Method for Evaluating Durability of Building Construction Sealants by Laboratory Accelerated Weathering Procedures in C 920 and we remove the test method C793. I propose that we make the following changes to C 920: Add in 2.1 C1519 Standard Test Method for Evaluating Durability of Building Construction Sealants by Laboratory Accelerated Weathering Procedures in C 920. Remove from 2.1 C793. Add a section 4.1.18 WUSE In - Weathering use class IN is for use in interior or low weather exposure applications These sealants pass a minimum of 2 weathering and movement cycles without failure. Add a section 4.1.19 WUSE Ex Weathering use class Ex is for use in typical exterior applications These sealants would pass a minimum of 6 weathering and movement cycles without failure. Add a section 4.1.20 WUSE He Weathering use class He is for use in severe weather exposure applications These sealants would pass a minimum of 10 weathering and movement cycles without failure. In section 6.4 add C1519 to read: The same conditions of time, temperature, and humidity shall be used for cure of test specimens for Test Methods C661, C719, C794, C 1247 and C 1519. Remove present section 8.11 and put in its place: 8.11 Effects of accelerated weathering The total loss in bond and cohesion areas among the three specimens tested for each surface shall be no more than 9 cm2 (1 in.2) when tested in accordance with Test Method C1519 with standard mortar, glass and aluminum, or any other specified substrates. Modify section 9.12 eliminating C793 and replacing it with C1519. Modify section 10.1 so the first sentence reads Packaged materials that are certified by the manufacturer to be in compliance with this specification shall be labeled as to type, class, grade, use and wuse (weathering use) in accordance with Section 7.
Keywordscontinuous immersion; elastomeric sealants; joint sealants; sealants; specification; Seals--building applications; Cold-applied sealants; Cured elastomeric joint sealants; Decks--specifications; Elastomeric seals/sealants--specifications; Joint seals/sealants--specifications; Plazas; Sealants--specifications;
Draft Under Development