Go Green: Using Waste and Recycling Materials

It was estimated that about 3,3 million tonnes of used tires are generated every year in Europe. Despite several years of efforts to address the waste tires management, large stockpiles continue to be a problem across the EU States. Many EU states are trying to reduce the landfill disposal of waste tyres through directives, national laws and codes, promoting the development of sustainable options for the disposal, recovery, and reuse of tires. In this regard, the most important factor is to facilitate the development of new markets for these by-products. Tires are 100% recyclable: the rubber, metals and textiles can all be recovered and used in many applications, as well as in consumer and industrial products and numerous examples are published in the literature. One of the possible areas of application is the realization of concrete elements, in particular the use of the steel contained in a tire as discontinuous reinforcing fibre in the concrete matrix. Concrete is generally considered a brittle material because of its low tensile strength. Consequently, steel fibres are widely used in the concrete technology as discontinuous reinforcement into the matrix with the objective to bridge the cracks that develop when a load is applied to the concrete element. The concrete obtained by adding these fibres is characterised by a satisfactory improvement of the brittle matrix, mostly in terms of toughness and post cracking behaviour. The main objective of this work is to develop and to characterize the concrete reinforced with steel fibres recovered from waste tires in terms of both fresh properties (such as workability and air content), hardened properties (such as compressive strength, flexural toughness and stress-strain behaviour in compression). Finally, the bond behaviour between the concrete matrix and the reinforcing steel bars is analysed. On the basis of the satisfactory obtained results it may reasonably be supposed that the application of such recovered steel fibres in concrete technology could lead to economic advantages, non-minor physical-mechanical properties respect to concrete reinforced with industrial steel fibres and could contribute to the well-known pollution problem related to waste tires.