Permeability Behaviour of Recycled SFRC and Its Implications in the Durability Resistance of Rigid Pavements

Recycled steel fibres obtained from post-consumer tyres can be used as reinforcement for concrete pavements. They can improve the mechanical behaviour when compared to plain concrete, especially the post-cracking compressive, tensile and flexural strengths. Recycled fibres may also enhance shrinkage, fatigue and impact performance. However, it is important to understand not only the mechanical behaviour, but also the durability performance of recycled steel fibre reinforced concrete (SFRC) before applying it to large scale applications. This research was developed in an attempt to join two important themes in civil engineering, sustainability and durability. This paper reports the results of mechanical performance and permeability, as an important measure of durability, of sixteen concrete mixtures. The scope of the study comprises of two types of mix, conventional (CC) and roller compacted concrete (RCC); two types of cementitious materials, a binary combination of CEM1 and PFA and a low energy cement; two amounts of recycled fibres, 2 and 6% by mass of concrete; and one type of industrially produced fibres (2% by mass of concrete) to serve as control. Recycled fibre specimens of CC presented lower permeability than plain and industrial SFRC, whilst the opposite was observed for RCC. CC reinforced with 6% recycled fibres presented, in general, the lowest permeability values associated with the highest observed values of flexural and compressive strength.