Publication: Properties of rubberized concrete containing recycled aggregate with steel fiber and selected cementitious materials.
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Date
2025-09
Authors
Bassam S. A., Dabbour
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Abstract
The rapid demolition of ageing structures and subsequent reconstruction, driven by urban expansion and conflicts such as the Gaza wars, has generated substantial amounts of concrete debris, posing significant environmental and resource management challenges. This study focuses on improving the performance of treated recycled aggregate concrete (TRAC) and rubberized concrete (RUBC) through the physical and chemical treatment of recycled aggregates (RA) and crumb rubber (CR), combined with the use of supplementary cementitious materials (SCMs) and steel fibers (STF). SCMs were added as supplementary binders in proportions of 10% silica fume (SF), 15% fly ash (FA), and 5% kaolin (KA), both individually and in combinations of two materials. To enhance the ductility and impact resistance of TRAC and RUBC, 0.5% STF by volume was added. In comparison, CR was included as a partial replacement for sand at 5%, 10%, 15%, and 20% by volume. A total of 45 concrete mixtures were prepared and grouped into normal concrete (NC), TRAC, and RUBC. The experimental findings showed that TRAC achieved compressive strength comparable to NC, confirming the effectiveness of the RA treatment. However, durability was slightly reduced due to the adhered mortar content. The inclusion of SCMs in TRAC, especially when combined with 0.5% STF, significantly improved strength, ductility, and durability, with some mixtures surpassing expectations NC. In contrast, incorporating CR decreased compressive strength and durability but markedly improved ductility, flexural and compressive toughness, and energy absorption capacity. The optimal results were obtained at 20% CR for compressive toughness and 15% CR for flexural toughness. The addition of 0.5% STF in RUBC further enhanced splitting and flexural strength while significantly increasing ductility indices. Furthermore, the integration of SCMs with STF in RUBC led to significant improvements in all properties, with SF providing the most impactful individual contribution. Simultaneously, using both SF and FA together resulted in the greatest overall enhancements in mechanical performance, ductility, and durability across most CR replacement levels. In conclusion, while the use of crumb rubber in concrete results in reduced strength and durability, it significantly enhances ductility and resistance to impact loading in RUBC. These drawbacks can be effectively mitigated through the incorporation of SCMs and STF, as SCMs refine the microstructure and improve durability, while STF enhances tensile resistance and crack-bridging capacity. The combined action of these materials enables RUBC to achieve a balanced performance, retaining its superior ductility while attaining satisfactory strength and durability. This synergy highlights the potential of RUBC for both conventional structural applications and for structures exposed to impact and dynamic loading conditions.