Properties of concrete reinforced with different kinds of industrial waste fibre materials

Nowadays, the use of different types of sub-products in cement-based materials has become a common practice in concrete industry. This paper discusses the feasibility of adding metallic and polypropylene by-product fibres as reinforcement of normal concrete. The effects of the incorporation of various types of waste metallic fibres (WMF) and polypropylene fibres (WPF) on the mechanical properties of fibre-reinforced concrete were experimentally investigated. A normal concrete with a compressive strength of 30 MPa was used as a control mixture. The influence of type, volume and length of WF on the compressive and flexural strengths, and toughness of fibres reinforced concrete (FRC) is evaluated. The results obtained have shown that the WPF decreases the compressive strength of WFRC, especially when using long fibres with high volume fraction. A slight decrease of the compressive strength was also observed with the composites containing more than 2% of the WMF. However, adding the WPF and the hybrid fibres increases the flexural strength of the WFRC. It has been observed that the composites reinforced with the WPF is more advantageous in terms of post-cracking behaviour and load-carrying capacity as compared to the composites reinforced with the WMF even in some cases, the WPF performs better than the multimodal composites. The results have shown that generally, ductility, toughness, and especially the post-cracking behaviour of the WFRC are significantly improved when using the multimodal composites compared to composites reinforced with the mono-fibres system. Results regarding orientation and distribution of fibres into the cement matrix, and porosity and their effect on the WFRC performance were also discussed.