Performance evaluation of bond strength and fiber type on the mechanical properties of polyurethane-based polymer mortar

Polyurethane (PU)-based Mortar (PUM) has a short curing time and high bonding ability as a new potential repair material. However, its low strength significantly limits its application in main-taining civil engineering structures. In this paper, the effect of micro steel fiber (MSF) with different aspect ratio and different dosages on the compressive strength, flexural strength, and elastic modulus of PUM was investigated. The performance of fiber at different embedment depths on the interfacial bond properties between the PU-based mortar mixture and steel fiber was explored through the fiber pull-out test. Additionally, steel fiber's reinforcing and toughening effects were analyzed, and scanning electron microscopy (SEM) was used to analyze the micro-structure of PU-based mortar reinforced with steel fiber. The results showed that the mechanical performance of PUM incorporated with two fiber types up to 3% was significantly improved. The bond strength between the micro steel fiber and PUM mixture improved with the increase in fiber volume fraction in the PU mixture. Similarly, the pull-out load and the pull-out work are increased with the increase in depth, while the interface bond strength is decreased. Additionally, based on the result obtained, the reinforcing effect of MSF in PUM can effectively refine the pores and bridge the crack formation.