Mechanical Properties of Cement Matrix Composites Reinforced with Polyoxymethylene Fibers of Different Lengths

Polyoxymethylene (POM) fiber is a new type of reinforcement material developed in recent years, which provides a new way and choice for the modification and reinforcement of cement-based materials. In order to improve the application of POM in the construction field, fiber-reinforced cementitious materials were prepared using 6- and 12-mm POM fibers. The effects of at two lengths of POM fibers on fluidity, compressive strength, flexural strength, flexural toughness, and tensile strength of cement mortar were investigated, and the bonding interface between fibers and the cement mortar matrix was observed using scanning electron microscopy (SEM). The results show that the addition of POM fibers reduced the fluidity and 7-day compressive strength of cementitious composites, but had little effect on 28-day compressive strength. With the increase of POM fiber volume fraction and length, better flexural toughness and ultimate tensile strength can be obtained. When the POM fiber length was 12 mm and the volume fraction was 0.90%, the equivalent flexural strength and ultimate tensile strength of the POM fiber–reinforced cement-based composite (POM-FRCC) increased by 46.3% and 13.5%, respectively, compared with the control group. Microscopic analysis revealed that the POM fibers were tightly bonded to the cement mortar matrix, and the fibers had a severe surface scraping in the resistance to damage.