Fibre distribution and orientation of macro-synthetic polyolefin fibre reinforced concrete elements

Abstract

Fracture behaviour of polyolefin fibre reinforced concrete (PFRC) has proved to be suitable for structural design in construction elements. As in other fibre reinforced materials, the tensile behaviour is strongly affected by the positioning of the fibres. Previous research has assessed this influence by means of fracture tests, showing reliable results. These were obtained by changing the most influencing parameters: the fibre length, the pouring and compaction methods, the concrete type and specimen sizes. However, the influence of these factors in fracture results is merely limited to the fracture surfaces, while the positioning of the fibres in the rest of the piece may be a key factor for design in structural elements. Furthermore, examination of the orientation factor within the whole piece provides relevant information about the behaviour of the fibres during the pouring processes. It may also allow preparation of future models to predict the final positioning of the fibres. This paper examines the positioning and orientation of the fibres in elements which provided fracture results previously reported in the literature. In addition to counting the fibres located in the fracture surfaces, the specimens were divided in portions. The fibre-positioning maps obtained provide sound and useful conclusions that may be considered in future design of PFRC elements. The data gathered showed how the orientation-factor varied with the flux and vibration, absence of any tendency to float and the noticeable influence of the pouring point in fibre distribution. It also showed that this type of fibre is suitable for structural-size elements, improving the orientation factor for longer distances when using self-compacting concrete.