EFFECT OF STEEL FIBERS EXTRACTED FROM WASTE TYRES ON HIGH-EARLY- STRENGTH SELF-COMPACTING CONCRETE (HESSCC)

Abstract

Self-compacting concrete (SCC) is an innovative material widely applied in high-rise and precast structures due to its ability to flow and consolidate without vibration. However, research on high-early-strength self-compacting concrete (HESSCC) remains limited, particularly regarding the use of sustainable materials. This study investigates the effect of incorporating steel fibers derived from waste tyres (SFWT) on the fresh and hardened properties of both SCC and HESSCC. Ten mixtures with fiber contents of 0%, 0.5%, 1%, 1.5%, and 2% by volume were prepared and subjected to slump flow, V-funnel, compressive, tensile, and flexural strength tests at 1 and 28 days. The results indicate that the addition of SFWT decreases the slump flow diameter and increases V-funnel time due to higher internal resistance; however, all mixtures remained within the acceptable limits of ACI 237R-07. At an early age, HESSCC achieved a compressive strength nearly twice that of SCC, while at 28 days, their strengths converged. Tensile and flexural strengths increased significantly with SFWT, with the maximum improvement observed at 2% SFWT, yielding 50.3% higher tensile and 48.65% higher flexural strength for HESSCC at 28 days compared to the control. These results demonstrate that SFWT improves crack resistance and enhances the hardened properties of SCC and HESSCC. In conclusion, using recycled steel fibers provides an effective and sustainable approach to producing high-performance concrete with rapid early strength development.