SWRI’s (Southwest Research Institute) Sealant Validation Program - ASTM C920

This standard is used for elastomeric sealants—the flexible materials used in joints in construction, like window seals, concrete joints, or expansion joints. The main things they check are adhesion, cohesion, peel strength, and hardness under movement.

Tests and procedure:

1. Cyclic Movement Test (Adhesion & Cohesion)
Purpose: To check if the sealant stays stuck to the surface (adhesion) and doesn’t break apart internally (cohesion) when the joint expands and contracts repeatedly.

Procedure: Prepare a standard test joint (often two metal or concrete blocks with a gap filled with sealant). Cure the sealant fully (let it harden as per manufacturer instructions). Move the joint back and forth repeatedly, simulating expansion and contraction of the building materials.
Inspect for cracks, pulling away from the substrate, or internal failure. Pass criteria: Sealant should remain adhered and intact without major cracks or failures.

2. Adhesion-in-Peel Test
Purpose: To measure how strongly the sealant sticks to the surface when it is peeled off.
Procedure: Apply the sealant to a standard substrate and allow it to cure. Cut a narrow strip and peel it off at a standard angle (usually 90°).
Measure the force needed to peel the sealant from the surface. Pass criteria: Force required should meet the minimum values specified in ASTM C920.

3. Indentation Hardness Test
Purpose: To check how hard or soft the sealant is, which affects flexibility and durability.
Procedure: Cure the sealant sample fully. Press a standard indenter (like a small metal tip) into the sealant with a defined force. 
Measure how deep the indenter goes into the sealant. Pass criteria: Depth of indentation must fall within the acceptable range (too soft or too hard can fail performance).

This test/program just makes sure the sealant:
1. Sticks well,
2. Doesn’t fall apart,
3. Can handle movement, and
4. Has the right flexibility.

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