Mechanical properties of fiber-reinforced high-performance concrete incorporating pyrogenic nanosilica with different surface areas

• Effect of two types of pyrogenic nanosilica (NS) on FRHPC properties was investigated.
• FRHPC was fabricated with steel and polypropylene (PP) fibers.
• Coarser type of NS showed better performance in enhancing mechanical strengths.
• Finer type of NS improved the electrical resistivity of FRHPC more than coarser one.
• Bonding between fibers and HPC matrix was developed by the utilization of NS.

The aim of the present study was to investigate the effect of pyrogenic nanosilica with different specific surfaces areas (200 and 380 m2/g) on mechanical properties of fiber-reinforced high-performance concrete (FRHPC) produced with two different types of fibers including steel and polypropylene fibers. Accordingly, different mechanical tests (compressive, splitting tensile and flexural strengths) as well as electrical resistivity were performed at 7, 28, and 91 curing days. In addition, the modulus of rupture and flexural toughness of FRHPC prisms were calculated based on the flexural testing results. Also, scanning electron microscopy test (SEM) was conducted to evaluate the microstructural performance of pyrogenic nanosilicas in the matrices of FRHPCs.Results demonstrated that the application of pyrogenic nanosilica can enhance the mechanical and electrical resistivity properties of FRHPC. In addition, the coarser type of pyrogenic nanosilica showed better performance in increasing the mechanical properties of FRHPC than finer one. However, the finer type of pyrogenic nanosilica resulted in higher electrical resistivity in FRHPC specimens compared to coarser nanosilica. Moreover, according to SEM test, the enhancement of mechanical properties of FRHPC in the presence of pyrogenic nanosilicas could be related to the densification of the matrix caused by their particles.