Astm C920 Standard Specification For Elastomeric Joint Sealants Summary ((free)) -

Confirms the sealant won't "bleed" oils that could stain porous surfaces like white marble or limestone. Why It Matters

: For continuous liquid immersion (e.g., swimming pools).

Samples are exposed to intense UV rays and heat to ensure they don't crack, chalk, or lose elasticity over time. Confirms the sealant won't "bleed" oils that could

ASTM C920 establishes the minimum performance requirements for cold-applied, elastomeric joint sealants used in building and civil engineering applications (e.g., curtain walls, pavement joints, window perimeters).

: Common classes include 25 (±25% movement) for most expansion joints and 50 (±50%) for high-movement curtain walls. The sealant must withstand cyclic joint movement (e

: Measures bond strength to specific substrates.

The sealant must withstand cyclic joint movement (e.g., ±12.5%, ±25%, ±50%) without cohesive failure. Class 25 (25% movement) is the default minimum unless otherwise specified. or lose elasticity over time.

Specialty joints that open significantly more than they close.