Flexural and Shear Bond Performance of Polyurethane-Mortar Interface under Micro- and Macroscale

Abstract

Polyurethane materials have been widely applied in the mending of cementitious materials, and the mending efficiency is highly impacted by the bond strength between the polyurethane materials and the cement base. This paper aims to evaluate both the shear and flexural bond strength between cement mortar and polyurethane with different water and modifier contents. The shear and flexural bond strengths were examined using a slant shear test and three-point bending test on mortar samples prepared with a polyurethane interface. The effect of the polyurethane/water ratio on the bond strength was first examined, and both the highest shear and flexural bond strength were achieved for the samples with a 30% polyurethane/water ratio. To further enhance the bond strength, ethylene-vinyl acetate (EVA) was further added to the polyurethane, and the effect of the replacement ratio on the bond strength was further examined. The macro-size strength tests indicated the highest strength was achieved for the polyurethane samples that had a 10% EVA replacement ratio. The mechanism behind the effect of water and EVA content was further examined with a scanning electron microscope (SEM) and atomic force microscope (AFM). The examined relationship between water and EVA content and bond strength can provide useful information for the field application of polyurethane materials.