Limiting crack width in RC beams by the use of ultra high toughness cementitious composites

Abstract

This paper presents an investigation on the ability of Ultra High Toughness Cementitious Composite (UHTCC) to translate macrocracks in reinforced concrete (RC) beams into multiple micro-cracks in composite UHTCC/ RC beams where a layer of UHTCC replaces concrete cover to protect a longitudinal tensile steel bar. Four point bending tests were performed on various UHTCC/RC composite beams. The reinforcement ratio of longitudinal tensile steel bar and the thickness of UHTCC layer were two varying parameters. It is discovered that the use of an UHTCC layer leads to the improved load capacity and deformation capacity when compared to reinforced concrete beam. As the reinforcement ratio increases, the degree of improvement becomes less significant. The thickness of UHTCC layer has little impact on load and ductility of the composite beam, provided that enough bond between concrete and UHTCC layer is ensured. For all tested UHTCC/RC beams, crack opening under service loading condition is effectively controlled within 0.1 mm.