Fire resistance tests on concrete-filled steel tubular columns with geopolymeric recycled aggregate

This paper presents an experimental investigation on geopolymeric recycled aggregate concrete filled steel tubular (GRACFST) columns in fire. A total of 12 specimens were tested, including 6 circular columns and 6 square columns subjected to combined fire and loading. The test parameters include: (a) cross-section type (circular and square); (b) column load ratio (0.3, 0.4 and 0.6); and (c) fire scenario (all around fire exposure and two surfaces fire exposure). The failure mode, temperature development, deformation development and fire resistance of GRACFST columns were obtained and discussed. Finally, the fire resistance design method for conventional CFST columns proposed in Eurocode 4 was used to predict the ultimate cross sectional load bearing capacity of the GRACFST column at a specified fire exposure time, and the comparison between the prediction and the test results reported in this paper indicated that the Eurocode 4 method gave an overestimation to the GRACFST column. To improve the prediction accuracy, suitable material models for the passively confined GRAC in CFST columns should be developed in the future research.