TEMPERATURE-DEPENDENT PERFORMANCE OF POLYMER CONCRETE WEARING SURFACE SYSTEM ON THE POPLAR STREET BRIDGE

The report details a five-year study of the performance of the epoxy (polymer) concrete wearing surface placed on the orthotropic steel-plate deck of the Poplar Street Bridge in St. Louis, Missouri. This study involved inspections, field testing and laboratory experiments and analyses. During the first few years, the focus was on the field study components. Later when some cracks were observed on the wearing surface, a detailed experimental and analytical investigation was incorporated to understand the cause of the cracks and study potential crack-repair procedures. Laboratory experiments were undertaken to study the temperature-dependent mechanical properties of the polymer concrete materials used on the bridge deck. Experiments included a series of static flexural tests, axial compression tests and flexural fatigue tests on the polymer concrete specimens under three different test temperatures. Temperature-dependent mechanical properties such as modulus of rupture, compressive strength, modulus of elasticity and fatigue strength were obtained from the tests. The analyses components focused on the reasons for longitudinal fatigue cracking and transverse wearing surface cracking. It has been shown that a combination of traffic loads resulting in transverse bending of the deck plate and cold temperatures contributed to the longitudinal fatigue cracking observed on the deck. Transverse cracking of the wearing surface in the thickness transition zone of the eastbound lanes has been attributed to differential thermal expansion of the two webs of the south box girder coupled with thermal and elastic mismatch between the wearing surface and the steel deck plate. It has been concluded that temporary repair of wearing surface cracks using Pavon (asphalt-based product) or MMA sealant would minimize potential water infiltration onto the steel deck and extend the life of the wearing surface. An alternate repair approach where SIMCON (Slurry infiltrated steel fiber mat reinforced concrete) plates are bonded to the wearing surface holds promise as a long-term solution.