The Top-Bar Effect in Specimens with a Single Casting Point at One Edge in High-Performance Self-Compacting Concrete

Abstract

An investigation of the steel-to-concrete bond in high-performance self-compacting concrete (HPSCC) is presented based on direct pull-out tests. The investigation was performed on specimens made of three different HPSCC mixes with varying contents of silica fume (without, 5 and 10% by mass of cement). Specifically, the top-bar effect in specimens with a single casting point at one edge was examined. Horizontal specimens with transverse rebars distributed over their heights (480 mm) and lengths (1600 mm) were cast. The bond capacity of the HPSCC was decreased across the length up to the measured rebar distance from the casting point. The reduction occurred with the same magnitude in both the lower and upper section of the horizontal specimens. It was found that the top-bar effect did not change significantly with an increasing distance of the rebars from the casting point of the concrete mixture. It was demonstrated that the modification of the HPSCC using the silica fume significantly improved the quality of the bond conditions.