Evaluation of Geopolymer Concrete Based on Fly Ash Containing Steel Fibers and Rubber Crumbs Using Cement as a Partial Substitute for Fly Ash

In this study, geopolymer concrete made from fly ash was utilized, with different proportions of cement (۰%, ۱۰%, and ۲۰%) replacing fly ash to examine the influence of cement presence in geopolymer concrete. To increase tensile strength and impact resistance, ۰.۵ and ۱ percent steel fibers were used. Adding ۰.۵ percent fibers improved compressive strength by ۹ percent, and for ۱ percent fibers, it was ۲۶ percent. The tensile strength also significantly increased with the addition of fibers. Adding ۰.۵% fibers, on average, increased the tensile strength by ۲۵%, with the increase being ۳۴% for ۱% fibers. It was also noted that substituting cement for fly ash had little effect on compressive strength, but replacing ۱۰% cement could be considered as the optimal substitution level in terms of tensile strength in the samples.The test results for impact resistance indicated a significant effect of steel fibers on the number of impacts until the first crack appeared and the complete rupture of the samples. Adding fibers increased the resistance to complete rupture by ۱۲ to ۲۲ percent with ۰.۵ percent fibers, and between ۴۹ to ۶۴ percent for ۱ percent fibers. Replacing ۱۰ percent rubber crumbs improved the impact energy of concrete, increasing the energy until the first crack by ۱۰ percent on average and the energy until complete rupture by ۱۵ percent.In this study, geopolymer concrete made from fly ash was utilized, with different proportions of cement (۰%, ۱۰%, and ۲۰%) replacing fly ash to examine the influence of cement presence in geopolymer concrete. To increase tensile strength and impact resistance, ۰.۵ and ۱ percent steel fibers were used. Adding ۰.۵ percent fibers improved compressive strength by ۹ percent, and for ۱ percent fibers, it was ۲۶ percent. The tensile strength also significantly increased with the addition of fibers. Adding ۰.۵% fibers, on average, increased the tensile strength by ۲۵%, with the increase being ۳۴% for ۱% fibers. It was also noted that substituting cement for fly ash had little effect on compressive strength, but replacing ۱۰% cement could be considered as the optimal substitution level in terms of tensile strength in the samples. The test results for impact resistance indicated a significant effect of steel fibers on the number of impacts until the first crack appeared and the complete rupture of the samples. Adding fibers increased the resistance to complete rupture by ۱۲ to ۲۲ percent with ۰.۵ percent fibers, and between ۴۹ to ۶۴ percent for ۱ percent fibers. Replacing ۱۰ percent rubber crumbs improved the impact energy of concrete, increasing the energy until the first crack by ۱۰ percent on average and the energy until complete rupture by ۱۵ percent.