Microstructure and mechanical performance of polyurethane-fly ash composites (PU-FAC) under different effect factors

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.