Compressive behavior of partially encased recycled aggregate concrete columns after exposure to elevated temperature

Abstract

To explore the eccentric compressive behaviors of partially encased recycled aggregate concrete (PERAC) columns after exposure to high temperatures, 12 columns were tested in this paper, including 3 columns under axial load as controls. Factors considered in the experiment were replacement levels (r) of recycled coarse aggregate (RCA), temperature (T), and relative eccentricity (e/H). The test results show that the temperature rising of webs is effectively delayed by protection of recycled aggregate concrete (RAC). And the post-heated PREAC column has higher ductility under eccentric load due to the better deformation capacity of RAC than that of natural aggregate concrete (NAC). Similar to the effect of T, when the e/H adds from 0 to 0.2, both ultimate axial strength and initial stiffness of columns decrease significantly. When e/H adds from 0.2 to 0.4, flanges away from the loading axis are gradually changed from compression to tension. All columns eventually fail due to local buckling of flanges near loading axis. Compared with partially encased concrete (PEC) columns, the r of 50% is beneficial for PERAC columns to get better ductility and maintain stiffness. In addition, the modified method based on the code T-CECS719–2020 can be used to predict the ultimate strength of PERAC columns after exposure to high temperatures.