Structural Performance of Nanosilica-Blended Square and Circular CFST Stub Columns

Abstract

The study focuses on the structural behavior of concrete-filled steel tubular (CFST) stub columns with conventional cement concrete and nano-silica blended (doses of 4%, 6%, 8%, and 10% nano-silica by weight) concrete core infill of M25 grade under a pure axial compressive load. The strength and deformation capacities, as well as failure modes, of the CFST columns were assessed with reference to steel hollow and reinforced concrete (RC) stub columns. At optimum replacement of cement with nano-silica, the increase in strength from filling the hollow steel columns is about 1.6 and 1.5 times for square and circular sections, respectively. The addition of 6% nano-silica to the cement concrete core of CFST columns showed 2.55 and 1.19 times more strength as compared to RC stub columns with square and circular sections, respectively. As a result, adding nano-silica to the concrete mix increases the core’s axial compressive load carrying capacity and strengthens the nano-silica blended CFST stub column. The addition of the optimum doses of nano-silica increases the higher rate of hydration and rapid formation of hydrated products in the cementitious matrix due to its higher specific surface area. Due to its higher specific surface area, adding the right amount of nano-silica speeds up the formation of hydrated products in the cementitious matrix and makes the rate of hydration faster.