Development and performance of a novel hybrid toughened unsaturated polyester resin (UPR) composite for crack repair of asphalt pavement

In order to effectively seal the cracks, a novel hybrid toughened unsaturated polyester resin (RMUP) crack repair material using liquid nitrile rubber (LNR) and nano-montmorillonite (nano-MMT) is developed in this study. The optimum RMUP formula is determined through mechanical performance tests, viscosity test, fluorescence microscopy, etc. The mechanical properties of the RMUP composite are compared individually with those of toughened UPR by LNR or nano-MMT, while the workability, mechanical performance, durability and cost are compared to other commonly used crack repair materials such as epoxy resin (EP), polyurethane (PU), silicone (SI) and SBS-modified emulsified asphalt (SEA) sealants. The hybrid toughening effect and potential of RMUP as a crack repair material is validated. Furthermore, the hybrid toughening mechanisms are analyzed using Fourier transform infrared spectroscopy (FT-IR). The test results show that the hybrid combination of LNR and nano-MMT effectively toughens UPR, not only improving its ductility but also maintaining its high mechanical strength. Additionally, as a repair material, RMUP exhibits excellent workability, being less temperature-dependent, with a moderate operating time and rapid strength increase following repair, and possesses high mechanical strength (the tensile strength up to 19 MPa) and favorable durability with only a 2%− 4% performance degradation exposing to water immersion environments and no weight loss in extremely hot weather, as well as cost-effectiveness, featuring similar properties to EP sealant but at half the cost of EP. The mechanism analysis reveals that the LNR chemically interacts with the UPR matrix, cross-linking to the UPR's polymer chains. Simultaneously, the nano-MMT galleries are intercalated by the UPR polymer chains, resulting in an intercalated nanocomposite formation. Both interactions contribute to RMUP's improved toughness.