Experimental investigation of workability and strength of rubberized concrete: Effects of fine and aggregate replacement with crumb rubber

Rubberized concrete (RuC), incorporating crumb rubber from recycled scrap tires, offers a sustainable solution to the environmental challenge of tire waste disposal. Despite its potential, its optimizing mechanical properties, particularly strength, remains a critical challenge. This study explores the workability and strength characteristics of RuC produced by replacing fine and coarse aggregates with recycled crumb rubber (RCR). Replacement levels ranged from 10% to 100%, and water-to-cement (w/c) ratios of 0.48 and 0.30 were examined. The results revealed that increasing RCR content significantly decreased workability and compressive strength, primarily due to poor bonding between rubber particles and the cement matrix. However, a lower w/b ratio and the controlled use of superplasticizers partially mitigated these effects, improving both workability and tensile strength. The influence of the superplasticizer was clearly isolated through its application at consistent dosage levels across all relevant mix designs, ensuring that its effects were accurately assessed without interference from other variables. Compressive strength exhibited a reduction of more than 85% compared with the control mixes at 100% replacement, whereas the replacement of 10% fine RCR preserved over 80% of the reference strength. Splitting tensile and flexural strengths demonstrated reductions exceeding 70% at higher replacement levels, nevertheless, mixes incorporating 10-20% fine RCR at a w/c ratio of 0.30 achieved strengths close to those of the control specimens. Fine RCR performed better than coarse RCR in terms of workability and strength, particularly when replacement levels were kept below 30%. Furthermore, the impact resistance of RuC to cracking and final failure improved by 15%-17% at a 10% replacement level compared to the control. These findings highlight the potential of RuC as a sustainable material for selected non-structural and limited structural applications, emphasizing the importance of mix design optimization to balance sustainability with performance.