Effect of calcium sulfoaluminate-based expansive agent on rate dependent pullout behavior of straight steel fiber embedded in UHPC

Abstract

To use a calcium sulfoaluminate (CSA) expansive agent (EA), beneficial for volume stability of concrete, its effect on the pullout behavior of straight steel fiber in ultra-high-performance concrete (UHPC) needs to be analyzed under various loads, from static to impact (0.018 to 1244 mm/s). Adding CSA EA enhanced the static pullout resistance of only inclined fibers, whereas the average bond strengths and pullout energies of both the aligned and inclined fibers improved by it under impact loading. Thus, adding the CSA EA is more effective in enhancing the dynamic pullout resistance. The fiber pullout resistance improved at a higher loading rate, and 45 degrees-inclination of the fibers improved the dynamic pullout resistance. A higher rate sensitivity on the bond strength was observed with the CSA EA addition and fiber's inclination, and the pullout energy was more dependent on loading rate than the average bond strength as fiber rupture was prevented.