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Conventional bridge expansion joints have the disadvantages of easy damage and lengthy maintenance period. Polyurethane concrete, as a polymer material, is gradually being applied to the repair of expansion joints. However, polyurethane-based repair materials are susceptible to a variety of factors during the early strength-building phase. In this regard, a Polyurethane-Fly Ash Composite (PU-FAC) for rapid repair was proposed in this paper and the effects of different factors on early mechanical performance were investigated. The orthogonal test was first used to determine the optimal mixing ratio of PU-FAC. Then the effects of temperature, catalyst, and curing time on the performance of PU-FAC were investigated by temperature rise curve, maturity index, SEM, and response surface method. The results showed that temperature and catalyst at different curing times had both positive and negative effects on the failure pattern, curing rate, degree of foaming, and mechanical performance. Finally, the optimum values of temperature and catalyst were determined by gray correlation analysis as 15 °C and 0.6 %. By analyzing the effects of different factors on the performance of PU-FAC, it provides a basis for the rapid repair construction of bridge expansion joint anchorage area.

For the study of the applicability of polyurethane concrete (PUC) in the anchorage zone of expansion joints, the construction process of PUC was summarized through the on-site construction of the anchorage zone of bridge expansion joints. The mechanical response of anchorage zones with different materials under vehicle loading was also analyzed by finite element modeling. The linear fatigue cumulative damage of expansion joint anchorage zone materials PUC, steel fiber concrete (SFC), and silicate cement concrete (PCC) were analyzed respectively by traffic investigation of bridge sections under construction and Miner's linear fatigue damage accumulation theory. The results show that the vertical displacement of PUC is 13 times that of SFC and PCC, the stress is reduced by 36%, and the annual cumulative fatigue damage value of PUC is 1.06E-07, which is only 1/10 of that of SFC, and PUC has excellent load cushioning capacity and fatigue performance, which can effectively improve the service life of the anchorage zone of expansion joints.

The use of polyurethane concrete (PUC) with a high compressive strength together with a corrugated steel plate (CSP) with a high tensile strength can improve the bending capacity of the corrugated steel-concrete composite structures. Although the PUC is lighter than normal concrete, its compressive, tensile, and bond strengths are much higher. In the paper, two groups of corrugated steel-concrete composite structure specimens with the PUC were designed, and the positive and negative bending capacities of the composite structure specimens were tested by a symmetrical four-point loading test and compared with that of the composite structure specimens using the normal concrete. The test results show that the bending capacity and deformation property of the composite structure specimens with the PUC are greatly improved compared with those using the normal concrete. Compared with the positive and negative bending capacities of the corrugated steel-normal concrete composite structure specimens, the composite structure specimens using PUC in the compression zone increased by 137.88 % and 136.42 %, while the corrugated steel-PUC composite structure specimens increased by 311.69 % and 283.39 %. Since the PUC has high bond strength, the test results of the negative flexural rigidity of the corrugated steel-PUC composite structure specimens were evaluated higher than the derived theoretical results. The test results of the corrugated steel-normal concrete composite structure specimens and the composite structure specimens using PUC in the compression zone are consistent with the theoretical results. In addition, using the PUC in the compression zone greatly improves the negative bending performance of the composite structure.