Influence of polypropylene fibers on the performance on nano - SiO2-incorporated mortar

Although Polypropylene (PP) fibers have advantageous characteristics, the weak bond with the cement matrix as a result of their smooth surface and chemical inertness remains a large limitation. It has been demonstrated that the fiber-matrix bond strongly affects the ability of fibers to stabilize crack propagation in the matrix. As the bond between fiber and matrix is mainly mechanical, it seems that incorporating nano-SiO2 into fiber reinforced cement composites provides a better bond with the matrix through pore refinement and better distribution of the hydration products. Hence, in this paper an effort was made to study the effect of PP fibers on the mechanical and physical properties of mortars incorporating nano-SiO2. Four fiber volume fractions, 0, 0.1%, 0.3% and 0.5% were considered. Compressive and flexural strength, water absorption and shrinkage of mortars were reported. SEM observation was also conducted to evaluate the effect of nano-SiO2 on the microstructure of cement paste. Results showed that nano-SiO2 significantly improved the mechanical and water absorption characteristics of mortars. It was observed that the microstructural characteristics of cement paste can be effectively improved by incorporating nano-SiO2, as the presence of nano-SiO2 enhanced the PP fibers effectiveness in strengthening mortar properties.