Microstructure and Fatigue Performance of Polyurethane Grout Materials under Compression

Polyurethane materials can be used for nondestructive maintenance of infrastructure, such as slab lifting through injection in a road or railway. Understanding the mechanical behavior and microstructure characteristics of this material is critical to ensure safe service of the infrastructure. This study investigates stress-strain behavior, microstructure characteristics, fatigue behavior, and failure mode of rigid polyurethane grout materials subject to both static and cyclic compressive loads. The densities of the investigated polyurethanes range from 80 to 500 kg/m(3), which are normally used in grouting. The yielding stress corresponding to 5% strain is measured and predicted based on the microstructure characteristics. The fatigue process of polyurethane can be divided into elastic, incubation, and failure stages. The failure threshold is identified for polyurethanes with different densities and at different stress levels. The failure mode is described based on the microstructure observation. (C) 2017 American Society of Civil Engineers.