Eccentric Compression Behavior of Reinforced Ultra-High Performance Geopolymer Concrete and Ultra-High Performance Concrete Columns: A Comparative Study

Ultra-high performance geopolymer concrete (UHPGC) has emerged as a low-carbon cementitious material with high mechanical performance and thus offers potential as a substitute for Portland cement-based ultra-high-performance concrete (UHPC). Experimental evidence on the eccentric compression response of reinforced UHPGC (R-UHPGC) columns, however, remains limited. In this study, six reinforced columns were tested under eccentric compression, with concrete type and eccentricity ratio taken as the main variables. The structural response was examined in terms of failure pattern, peak resistance, axial load–deflection behavior, and ductility. The results showed that at the same eccentricity ratio, the peak resistance of the R-UHPGC columns was approximately 20% lower than that of the corresponding R-UHPC columns. As eccentricity increased, the axial load resistance decreased, whereas the mid-height deflection and ductility increased. On the basis of the test results, available prediction methods for moment magnification factor and ultimate resistance originally developed for R-UHPC columns were assessed for their suitability for R-UHPGC members. A preliminary analytical approach was then established for estimating the second-order effect and load-carrying capacity of R-UHPGC columns.