Efficient design of alkali-activated reactive powder concrete for sustainable construction

This study investigates the efficient design of ground granulated blast furnace slag (GGBFS)-based ambient-cured alkali-activated reactive powder concrete (AARPC) by examining the effects of mix proportions and alkali activators, including alkali-activator to binder (Al/Bi) ratio, silicate modulus (SiO₂/Na₂O), and binder to aggregate (Bi/Agg) ratio, on workability and compressive strength. Microstructural analyses, including X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy, were performed to reveal phase changes and reaction products. A total of 27 mix combinations were evaluated. The flow diameter ranged from 100 to 242 mm, and compressive strength ranged from 65.8 to 106.0 MPa at 7 days and 72.3 to 124.4 MPa at 28 days. Lower Al/Bi ratios with lower silicate modulus enhanced workability through better dissolution of slag particles, whereas higher Al/Bi ratios with higher modulus improved flow by way of binder dispersion. Compressive strength increased with a higher Al/Bi ratio for Bi/Agg = 0.9 and 1.0, whereas a higher silicate modulus reduced strength due to insufficient dissolution. Denser microstructures were observed at lower Al/Bi ratios, whereas micro-cracks and unreacted slag were more prevalent at higher silicate modulus. Overall, this study provides significant insights into the efficient design of practical ambient-cured GGBFS-based AARPC.