Characterization of Enhanced ITZ in Engineered Polypropylene Fibers for Bond Improvement

The interfacial transition zone (ITZ) is well known to be a zone of high porosity and lesser strength and is the weak zone in the fiber-reinforced matrix. This study aims to evaluate the improvement in the bonding between engineered polypropylene fibers and the surrounding mortar matrix. The improvement was implemented by modifying the ITZ, which develops between the fibers and the cementitious matrix. Two commercially available repair materials have been used in this study, Mix M and Mix P. Mix M served as the base material for the prepared fibers, whereas Mix P is a fiber-reinforced repair mortar and provides a comparison. A total of six types of mixes have been investigated. The improved bonding is tested by coating the polypropylene fibers with supplementary cementitious materials (SCM) using an innovative patented concept. In this study, silica fume and metakaolin are used as the SCM because of their fine size and pozzolanic capacity. The study involves multiple items of investigation, including mechanical tests such as compressive strength, direct tensile strength, and three-point bending tests. Energy-dispersive X-ray spectroscopy (EDS) of the different mixes helped in evaluating and analyzing the ITZ between the fiber and matrix.