This paper aims at investigating the effect of crumb rubber size and content on hardened characteristics of self-compacting concrete. To this end, different self-compacting concrete mixtures were designed at constant water-to-binder ratio of 0.35 and 520 kg/m3 of binder content. The class F fly ash was replaced with cement as 30% by weight. Six designated crumb rubber contents of 5%, 10%, 15%, 20%, and 25% and three different sized crumb rubbers (No. 18, No. 5, and mixed crumb rubber) were considered as experimental parameters. According to the obtained results, the use of crumb rubber had a negative effect on the hardened properties of self-compacting concretes and the significant improvement was achieved with addition of all tire wastes types, for ductility

This study aims to review the research studies available in literature that examines the mechanical properties and optimum mixing ratios of ultra-high performance fiber-reinforced concretes (UHPFRCs). In addition to a comparison between mechanical properties of UHPFRC, high-performance concrete (HPC), and normal strength concrete (NSC). The studies included in this review were compiled under different headings and explained concisely. Subsequently, the best UHPFRC mixture was determined to be obtainable with 2% to 3% steel fiber content and a water/cement ratio of <0.2. Additionally, the UHPFRCs that were subjected to curing at 90 °C for 28 days yielded compressive, tensile, and flexural strengths that were 49% better than the samples cured at 20 °C. The review elucidates the key points of producing the best UHPFRC material for future applications.