Influence of Polypropylene, Carbon and Hybrid Coated Fiber on the Interfacial Microstructure Development of Cementitious Composites

Abstract

Concrete is the most used construction material in the world; however, its deficiency in shrinkage and low tensile resistance is undeniable. Used as secondary reinforcement, fibers can modify concrete properties in various ways. Carbon-fiber-reinforced concrete is highly suitable to maintain longevity of infrastructure where corrosion of steel can shorten the useful service life of the structure while polypropylene fibers can mostly improve the shrinkage of concrete. However, the biggest challenge with fiber-reinforced concrete is the appearance of the poorly structured interfacial transition zone around the fibers. In this study, environmentally friendly and low-cost attempts were made to coat fibers with fly ash to enhance the structure of mortar around the fibers. Coated carbon and polypropylene fibers were used in mortar in single and hybrid forms to investigate the efficiency of fiber coating methods on mechanical and durability properties of fiber-reinforced cement mortar. A minimal dosage of 0.25% and 0.5% (by volume) PAN-based carbon fiber and polypropylene fiber was added to mortar to make low-cost mixes. Compressive, tensile and three-point bending tests were done after 14 and 28 days of curing, and the results were analyzed. The results showed higher compressive strength in coated fiber-reinforced samples and comparable results in tensile strength, flexural strength, and toughness parameters. Scanning Electron Microscopy (SEM) photos and Energy-Dispersive X-ray (EDX) analysis approved the efficacy of the coating methods.