Compressive fatigue resistance and related microscopic mechanisms in foamed polyurethane grouting materials for roadbed rehabilitation

Abstract

Foamed polyurethane (PU) grouting materials are widely used for the non-destructive rehabilitation of roadbeds due to their expansion characteristics, lightweight, and high strength. However, their compressive fatigue resistance is still unclear. In this work, the relationships between density and strength/modulus were established by uniaxial compression tests. The fatigue damage evolution was divided into three stages by cyclic compression tests: adjustment stage, stable change stage, and cyclic failure or cyclic hardening stage. At high stress levels, the stiffness damage, deformation damage, maximum strain, and loss factor increased to about 16.07%, 60.14%, 5.25%, and 0.044 respectively after adjustment and stable change. Broken cells and cracks were observed in SEM images after cyclic failure. At low stress levels, the deformation damage is within the elastic range. The stiffness damage and loss factor always varied at a lower level and even tended to decrease. Obvious cracks were not observed in SEM images after cyclic hardening. The conclusion was drawn that density was the main factor affecting the compression fatigue performance of PU grouting materials, and high stress levels were the main reason for cyclic failure under the same density condition. Moreover, there was a functional relationship between the stress level and fatigue life of PU grouting materials. Some descriptions have been added in the revised manuscript.