Influence of silica fume content on bond behaviour of reinforcement in HPSCC

The steel-to-concrete bond in high-performance self-compacting concrete (HPSCC) was investigated based on direct pull-out tests. The analysis was performed on specimens made from four different HPSCC mixes with varying contents of silica fume (SF) (0, 5, 10 and 15% by mass of cement). The specimens used allowed the determination of changes in bond at individual levels of elements with a total height of 160, 480, 800 and 1600 mm. The rebars in the elements were placed perpendicularly to the direction of concreting. A reference element, characterised by a parallel orientation to the direction of concreting, was also prepared. It was found that the modification of HPSCC using SF improved the quality of bond conditions, especially in the case of elements with substantial height. There was, however, no effect of rebar orientation with respect to this casting direction and to the change in bond stiffness.