Effect of fibre reinforcement on the crack width profile and internal crack pattern of conventionally reinforced concrete beams

Paper i proceeding, 2016

Although fibre reinforcement is known to reduce the crack width and crack spacing of conventionally reinforced concrete elements, the impact of fibres on the crack width profile and crack morphology has not received as much attention. This paper presents experimental results of the crack width profile and internal crack pattern obtained from three-point bending test of conventionally reinforced concrete notched beams made of plain concrete and fibre reinforced concrete at low fibre dosages. The induced cracks were, under loaded conditions, injected with a fluorescent epoxy-resin. From each beam, two pieces were extracted and subjected to a second impregnation. Digital images were taken using a microscope and were then processed and analysed to extract quantitative information. The results revealed that the accumulated crack width was similar for all mixes. However, in the samples with fibres the main crack branched off into several narrower cracks compared to plain concrete, which generally exhibited a single and wider crack. Based on the known relation between permeation and crack width, this finding describes a mechanism through which fibre reinforcement can improve the water tightness of reinforced concrete structures and potentially extent their service life reducing the ingress of detrimental agents.