Temperature Aging, Compression Recovery, Creep, and Weathering of a Foam Silicone Sealant for Bridge Expansion Joints

• Published in: Journal of materials in civil engineering Vol. 23; no. 3; pp. 287 - 297
• Main Authors: Malla, Ramesh B, Shrestha, Matu R, Shaw, Montgomery T, Brijmohan, Smita B
• Format: Journal Article
• Language: English
• Published: Reston, VA American Society of Civil Engineers 01.03.2011
• Subjects: Applied sciences; Bridges; Buildings; Buildings. Public works; Creep (materials); Elongation; Exact sciences and technology; Expansion joints; External envelopes; Foams; Joints; Materials; Plastics; Sealers; Strain; TECHNICAL PAPERS; Tensile stress; Weathering; Compression recovery; Compression; Creep; Creep test; Temperature effect; Bridge expansion joints; Expansion joint; Silicone foam sealant; Relaxation; Stress relaxation; Aging; Siloxane polymer; Joints; Stress strain relation; mechanics; Experimental study; Compression test; Sealing; Stress; Strain; Mechanical test; Accelerated aging test; Bridges; Experimental result; Accelerated aging; Comparative study
• ISSN: 0899-1561; 1943-5533
• DOI: 10.1061/(ASCE)MT.1943-5533.0000166

Silicone foam was investigated as a sealant for small movement expansion joints in bridge decks. This paper presents results from the laboratory assessment of a model foam sealant subjected to thermal aging (exposure to high and low temperatures and temperature cycling), fatigue conditions, and outdoor weathering. Parallel tests were performed on a commercial solid-silicone bridge-joint sealant. Test results showed that the solid sealant recovered faster than the foam sealant after being subjected to prolonged compression at elevated temperature. When subjected to a constant tensile force, both the foam and solid sealants exhibited high initial creep rates (rate of elongation), but appeared to reach an equilibrium level of elongation at longer times. The foam sealant creeps at a slower rate and takes more time to get to the equilibrium elongation, whereas the solid sealant creeps much faster initially and reaches equilibrium faster. Thermal aging was found to have significant effects on the sealant modulus (increases with temperature); however, the effects on ultimate stress and strain were not apparent for both types of sealants. Temperature cycling between 24 and -29°C was observed to diminish the ultimate stress and strain of both the sealants by roughly 25%; however, no significant changes in modulus were found. Results from the tests on a limited number of outdoor-weathered sealant specimens showed that weathering appeared to produce an increase in sealant tensile and shear moduli (i.e., hardening effects because of weathering) and a decrease in ultimate strain. The weathered samples show tension loading-unloading behavior similar to the unaged samples. The tensile stress relaxation rate of the outdoor-weathered sealants could not be distinguished from those laboratory-cured (unweathered) counterparts.