Axial Compressive Behavior of Steel Reinforced GGBS-RFBP-FA Ternary Composite Geopolymer Recycled Fireclay Brick Aggregates Concrete Columns

In this study, the axial compressive behaviors of steel reinforced ternary composite geopolymer recycled fireclay brick aggregates concrete columns were investigated. The ternary binder material used in this study was produced by the combination of industrial by-products (i.e., granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA)) and alkali-activated solution. A total of 60 square steel reinforced composite columns (with a 200-mm side length and 600-mm height) were tested under axial compression. The tested variables included the mix proportion of ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates (GRA-RFBAC), the recycled coarse aggregate replacement ratios (0%, 30%, 50%, 70%, 100%), the longitudinal reinforcement ratios (1.13%, 2.01%), and the hoop stirrup reinforcement ratios (0.81%, 1.62%). Each group contained three identical samples. The ductility, failure mode, and axial load-bearing capacity of the columns were recorded and analyzed. The experimental results revealed that the damage progression and patterns of steel reinforced GRA-RFBAC columns were similar to those of ordinary Portland cement based recycled concrete columns. The ultimate bearing capacity of steel reinforced GRA-RFBAC columns decreased with an increasing replacement ratio of recycled coarse aggregate and increased with an increasing reinforcement ratio of longitudinal and hoop stirrups. Meanwhile, the stress-strain model of steel reinforced GRA-RFBAC columns under axial compression was proposed based on the experimental results. The present study suggests an efficient and environmental-friendly compression member.