Mechanical properties of recycled aggregate concrete reinforced with steel fibers under triaxial loading

Abstract

The use of steel fiber reinforced recycled concrete (SFRAC) can help achieve resourceful reuse of construction waste and environmental sustainability. However, SFRAC structural members may experience complex stress states. Therefore, triaxial compression tests were conducted on 168 cylindrical SFRAC specimens to investigate their mechanical properties. The failure modes, stress-strain behavior, strength, and deformation of SFRAC under triaxial compression were observed. The effects of lateral confining pressure, steel fiber (SF) content, and recycled coarse aggregate (RA) replacement rate on these properties were analyzed. The internal micro-morphology of SFRAC was analyzed using SEM to better understand its failure mechanism under compression. The result shows that an increase in lateral confining pressure alters the failure mode of SFRAC specimens, resulting in a significant increase in peak strength and ductility. The enhancement of the elastic modulus by steel fibers decreases as the lateral confining pressure increases, suggesting a coupling effect between the two parameters. The inclusion of steel fibers in SFRAC did not have a significant impact on its failure mode or compressive strength. And yet, it did increase the ductility and toughness of the material, with an optimal steel fiber content of 1% (by volume). On the other hand, the addition of recycled coarse aggregate resulted in a significant reduction in the concrete's compressive strength, by almost 17%. Finally, several common material failure criteria for concrete were used to evaluate the impact of RA substitution rate and SF content on the strength of SFRAC. The Willam-Warnke failure criterion showed a higher strength. These findings provide a theoretical basis for future engineering applications of SFRAC.