Despite offering several benefits in terms of environment and economics, few studies were conducted on the ground granulated blast furnace slag (GGBFS) based alkali-activated concrete reinforced with recycled tire steel fibers (RTSFs). Therefore, this paper employed the Taguchi method to investigate and optimize the influence of GGBFS content, the alkaline solution to GGBFS content ratio, sodium hydroxide solution concentration, and RTSF volume fraction on splitting tensile strength (STS) of recycled tire steel fiberreinforced alkali-activated slag concrete (RTSFR-AASC). The microstructural evaluation was done through scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR) analyses. The results indicated that the fiber content, the most efficient parameter on STS, led to a considerable enhancement in the performance characteristic. Microstructural analysis proved the variations in formation of C-S-H gel. The results of the confirmation experiment on the proposed optimized RTSFR-AASC mixture with the highest 28-day STS (7.11 MPa) confirmed the effectiveness of the Taguchi method. K E Y W O R D Sfiber-reinforced alkali-activated concrete, ground granulated blast furnace slag, microstructural analysis, recycled tire steel fiber, splitting tensile strength, Taguchi method

This study employed Taguchi-Grey relational analysis to optimize the influences of binder content, the molarity of sodium hydroxide (SH) solution, alkaline solution to binder content (Al/Bi) ratio, water to alkali-activated solids (W/S) ratio, and sodium silicate to sodium hydroxide solution (SS/SH) ratio on the workability, setting time, and compressive strength of alkali-activated slag-based concrete (AASC). Then, the recycled tire steel fibers (RTSF) were introduced into the optimized mixture in different dosages, and the physical and mechanical properties of fiber-reinforced AASC (FR-AASC) were evaluated. RTSF inclusion negatively affected the workability and increased the density while slightly reducing the water absorption. Additionally, the compressive strength and flexural behavior of FR-AASC improved by increasing the RTSF content. The analysis of images taken from flexural specimens through the Digital Image Correlation technique (DIC) revealed that higher RTSF dosage caused a curved macro crack with several branches alongside, leading to a better post-cracking performance in terms of strength and toughness.

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