Corrosion Durability of Recycled Steel Fibre Reinforced Concrete

Abstract

Steel fibre reinforced concrete (SFRC) is known by its excellent performance when
compared to conventional concrete. The use of steel fibres in concrete may contribute to improve properties such as crack and impact resistance, shrinkage reduction and toughness, by preventing/delaying crack propagation from microcracks to macro-cracks. In some cases it may be used as a replacement to conventional steel reinforcement or to high quality aggregates in roller compacted concrete.
Industrial steel fibres can be found in a wide range of types, aspect ratios and properties. However, steel fibres are dispersed in all directions and for the same flexural capacity a larger volume of fibre is required than for conventional reinforcement, thus increasing costs. An alternative to industrial fibres comes from the recycling industry through the use of steel from post-consumer tyres. Even though fibres reclaimed in this process are not uniform and have variability in size, experiments at the University of Sheffield have demonstrated that they can be used to enhance the mechanical properties of concrete. In addition to enabling a good mechanical behaviour, these fibres could become an interesting reinforcing alternative due to their lower cost and associated environmental benefits.
Since the concrete produced with recycled fibres is a new material, the study of its durability becomes mandatory before applying it to large scale structures. This
research aims to provide means for better understanding of the deteriorative processes that may contribute to the performance reduction of SFRC with recycled fibres. For that, fatigue process, shrinkage, freeze-thaw and corrosion of these fibres are discussed. For the latter property, a complete experimental plan has been already carried out by accelerating corrosion by wet-dry cycles. The results in terms of visual observations show that corrosion affects negatively the appearance of SFRC specimens. The mechanical properties, through the analysis of flexural and compressive tests, are not affected by corrosion after 5 months of wet-dry cycles.