ScholarWorks@Y-Scholar Hub

초록

To address the limitations of conventional high-performance sodium-based alkali-activated concrete, this study developed an ultra-high-performance calcium-based alkali-activated slag concrete (UHP-ASC) using calcium hydroxide (CH) as the activator. Based on the XRD results, the peak intensity of amorphous C-S-H(I) increased with increasing CH dosage up to 7.5%, and beyond it, the intensity of the C-S-H(I) peak remained nearly constant. In contrast, the peak associated with relatively less dense C-S-H gradually decreased when the CH dosage exceeded 7.5%. These trends were consistently reflected in the TGA results, where the amount of C-S-H reached a maximum at the CH7.5 specimen and subsequently showed a gradual decrease at higher CH dosages. The C-S-H structure became denser and more abundant at CH7.5, with increased Al uptake leading to a maximum mean chain length (MCL) of 10.73. However, with CH dosages beyond 7.5%, the Ca/Si ratio of the alkali-activated slag concrete system increased, resulting in a progressive reduction in MCL. As a result of the improved quantity and quality of reaction products, the CH7.5 specimen with fibers achieved the highest compressive strength of 187.52 MPa. At this composition, the fiber-matrix bond strength also reached its peak, with bond strength and pullout energy measured to be 17.1 MPa and 480.23 mJ, respectively. Tensile performance was maximized at CH7.5, with tensile strength, strain capacity, and strain energy density reaching 18.56 MPa, 0.74%, and 113.53 kJ/m3, respectively. Crack behavior analysis indicated that tensile performance was governed by the combined effects of matrix strength, pullout stiffness, and bond strength. When all these parameters were optimized, their widths were effectively controlled. Environmental impact assessments comparing the developed material with conventional ultra-high-performance concrete (UHPC) and sodium-based UHP-ASC yielded major reductions in both CO2 emissions and embodied energy.