Shear Strength of Nanosilica Fiber Reinforced Concrete Beams

Abstract

The use of Nano silica as an additive material in manufacturing concrete is a new technology. Tests have shown that this material enhances the mechanical properties of hardened concrete. Therefore the material gained some popularity nowadays and is now well recognized. This thesis presents a study in this direction to investigate the shear behaviour as well as determining the cracking and ultimate shear capacities of Nano Silica Reactive Powder Concrete (NSRPC) beams. The research covered four parts. The first part dealt with experimental study of the effects of varying some "material" parameters on the mechanical properties of NSRPC. These material parameters were nanosilica content NS (0, 1%, 2%, 3%), silica fume content SF (5%, 10%, 15%) and volumentric ratio of steel fibers Vf (0%, 1%, 2%). The investigated mechanical properties of the hardened concrete were compressive strength f'cf , splitting tensile strength fspf , modulus of rupture frf and modulus of elasticity Ecf. In the second part, sixteen simply supported NSRPC beams were cast and tested up to failure under two point loading. The beams (except one) had no stirrups and were heavily reinforced longitudinally to ensure shear failure to occur in all beams. In addition to the above mentioned "material" parameters, there were also varied "beam" parameters: longitudinal steel ratio ρ , shear span to effective depth ratio (a/d) and the use of steel stirrups. Measurements were recorded for the cracking shear force Vcr , the ultimate shear capacity Vu, the deflection at ultimate load, maximum crack width and maximum longitudinal and diagonal tensile strains.