Two Component Polyurethane/Epoxy Composite Grouting Material: Injectability, Mechanical Properties, and Engineering Applicability

ABSTRACT Traditional epoxy resin (EP) grouting materials are hindered by high brittleness, excessive shrinkage, and slow curing. To address these issues, a polyurethane/epoxy (PU‐EP) interpenetrating polymer network (IPN) composite was developed using a two‐component isocyanate system (MDI/IPDI). At the optimal PU‐EP mass ratio of 10:90, the material exhibited an initial viscosity of 218 mPa·s, a setting time of 18 min, and a volume shrinkage of only 1.75%. Compared with pure EP, tensile, compressive, impact, and flexural strengths increased by 30%, 21%, 54%, and 15%, respectively, with an adhesive strength of 4.29 MPa. Microscopic analyses revealed a well‐developed IPN structure with ductile fracture features and uniformly distributed microbubbles that relieved internal stress. Thermal stability remained adequate up to 150°C. Field tests confirmed rapid crack filling (5 mm wide, 200 mm deep) within 2 min, with no secondary cracking after 30 days and a core compressive strength of 66 MPa. This composite offers a balanced combination of low viscosity, fast curing, high strength, and low shrinkage, making it suitable for rapid concrete crack repair.