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چکیده
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Cement-based rubber concrete has been researched for over twenty years. Rubber aggregate, mainly from over one billion discarded end-of-life tires every year worldwide, is usually used to substitute aggregates in concrete mixture. A general consensus is that the ductility, and dynamic energy dissipation capacity of rubber concrete increase and strength decreases with a rising proportion of rubber phase in concrete due to the elastic and soft nature of rubber material. How to reduce the significant loss of strength has remained unresolved. Therefore, this research program aims to investigate the combining effect of crumb rubber (CR) and fiber steel type 1 (FS1) ,fiber steel type 2 (FS2) and polypropylene fiber (PF) in the development of concrete suitable for structural applications. The research also aims to overcome the challenge of optimizing the strength and stability of concrete containing CR and FS1, FS2 and PF fibers. The study aimed to develop and optimize a number of successful rubberized concrete and FS1, FS2 and PF fibers, mixtures with a maximized percentage of CR and minimized reduction in strength. The variables in this study included various supplementary cementing materials specifically superplastisizer, different fine aggregate contents, varying percentages of CR (0% to 36%), different types of fibers like FS1, FS2 and PF and different FS1,FS2 and PF fibers volume fractions (0%, 0.35%, and 0.7%).The studies evaluated the flexural of reinforced concrete beams made with Normal strength and high strength rubberized concrete beams. The study investigating mechanical properties of rubberized fibrous concrete beams with different strength of concrete. The main results drawn from sixteen groups of mixtures and samples to form the same particle size distribution of crumb rubber were used to replace 12%, 24% and 36 % of fine aggregate by volume. According to the experiment results, it was demonstrated that concrete with rubber particles tends to have a higher workability and lower density. However, the study indicated that the addition of FS1,FS2 and PF reduced the fresh properties, which limited the maximum percentage of CR that could be used in mixtures to 12%, compared to a 36% maximum percentage of CR used in developing successful mixtures without FS1,FS2 and PF. However, using FS1,FS2 and PF in mixtures increased flexural strength, compression strength, split tensile strength, modulus of rupture, modulus of elasticity, possion s’ ratio, but decrease failure mode crack number, ductility and energy absorption that resulted from adding CR.
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