Mechanical characteristics and structural performance of rubberized concrete: Experimental and analytical analysis

Rubberized concrete is referred to as "green concrete" by replacing fine aggregate with used tire rubber. However, although significantly increasing ductility, rubber particles lowered compressive strength. The study aimed to find the optimum ratio of crumb rubber (C-Ru) to employ in large scale elements. Firstly, the effect of C-Ru treatment and content on concrete mechanical behavior is examined. The experimental program contains 96 cubes and 78 cylinders using different percentages of untreated/treated C-Ru with portions from 5 % to 30 % replacing the sand. Then, four beams were produced with 5, 10, and 15 % sand volume substitution by C-Ru to investigate the effects of rubber content on structural performance and compared with conventional beam. It is found that C-Ru treatment has less enhancement for concrete fresh properties (workability) for using small ratios of rubber and this enhancement increases to reach 20 % for higher rubber content ratio while the comparable enhancement for hardened properties (compressive strength). In addition, well washing of the C-Ru after treatment did not affect the fresh RuC properties, while the improved the hardened properties of RuC (compressive and tensile strengths). Increasing the C-Ru content ratio decreased concrete fresh and hardened properties. Untreated C-Ru not more than 15 % as a replacement of fine aggregates is preferred to avoid large strength reductions while benefiting workability, economy, and safety. While the addition of C-Ru to the concrete mix increased the ductility, toughness, and self-weight of the beams, it also decreased their flexural capacity. Finally, the finite element analysis using ANSYS is used to compare with experimental results and thus it could accurately model behavior of rubberized concrete as a complex material that recommended for further studies.