Bonding and Aging Behavior of Silicone Foam Sealant for Small Movement Bridge Joints

Sealing bridge joints is important to prevent water, debris, and deicing corrosive materials to penetrate below the deck and damage the structure. A novel silicone foam sealant (SFS) has been developed to provide a long-term, cost-effective sealing method for small-movement expansion joints. This SFS exhibits a reduced elastic modulus which generates smaller stresses at the interface of the joint when the expansion joint widens in colder weather. This paper describes the experiments conducted to examine the bonding and ultimate stress-strain properties of the SFS compared to the commercially available product from which the SFS is derived. Factors studied include (a) substrate material, (b) presence of substrate primer, and (c) prolonged presence of saltwater. It was found that the SFS did not fail adhesively (i.e. no detachment from the substrate), compared to the commercial product which failed approximately 90% of the time via debonding at the interface to the substrate. On aging, the solid sealant exhibited significantly faster rate of (as much as three times) decrease in secant modulus over the 5-month saltwater aging period compared to the SFS.