Tests of circular geopolymer concrete-filled steel columns under ambient and fire conditions

Sixteen circular geopolymer concrete-filled steel tubular (GCFST) columns made with carbon steel were tested at ambient temperature to obtain the axial load-moment interaction curves and buckling curves. Moreover, six circular composite specimens with stainless steel tubes were tested in fire to study the effects of concrete type and presence of internal reinforcement on the fire resistance. It was observed that the provisions in the Australian standard AS/NZS 2327 for composite columns can satisfactorily predict the ambient temperature strength of GCFST columns. From the fire tests, it was found that the use of geopolymer concrete could significantly improve the fire resistance of composite columns compared with the conventional counterpart made with ordinary Portland cement concrete. The results indicate that it is possible to eliminate the internal steel reinforcement or external fire protection to achieve required fire resistance by using high performance materials in composite columns. A life cycle analysis was further conducted, which showed that the life cycle cost of GCFST columns made with carbon steel was similar to that of the conventional counterparts, but the embodied carbon of the former was approximately 13.6 to 20.8% less than that of the latter.