Concrete Nosing Expansion Joint Repair with Polymer Concrete

Polymer concrete repair systems offer significant advantages over conventional cement concrete for repairing deteriorated concrete nosing expansion joints. The rapid strength gain allows traffic reopening within hours, and the improved durability extends the service life of the repair. Polymer concrete systems use a polymer binder (typically epoxy, polyester, or methyl methacrylate) instead of Portland cement. The polymer binder provides much faster strength gain than cement, with most systems achieving 30 MPa within 1-4 hours at 20 degrees C. This rapid strength gain is critical for minimizing traffic disruption during repair. Epoxy polymer concrete is the most durable option for bridge joint repairs. It has excellent bond strength to existing concrete, high compressive and tensile strength, and good chemical resistance. However, epoxy systems have a limited working time (pot life) that decreases at high temperatures. In hot weather, the pot life may be as short as 15-20 minutes, requiring rapid placement and finishing. Methyl methacrylate (MMA) polymer concrete is preferred for cold weather applications because it can be applied and cured at temperatures as low as minus 20 degrees C. MMA systems have a strong odor during application that requires adequate ventilation and respiratory protection. The cured MMA concrete has good durability and bond strength. Surface preparation for polymer concrete repair is critical for bond strength. The existing concrete must be prepared by hydrodemolition or mechanical scarification to remove all deteriorated material and create a rough, clean surface. Laitance, oil, and other contaminants must be completely removed. The surface must be dry or saturated surface dry (SSD) depending on the polymer system requirements. Quality control for polymer concrete repairs includes testing the compressive strength of cubes cast from the repair material, verifying the bond strength by pull-off testing, and checking the surface level and texture. The repair must be inspected before traffic reopening to verify that it is safe and meets the acceptance criteria.