EXPERIMENTAL STUDY ON STEEL TUBULAR STUB COLUMNS FILLED WITH GEOPOLYMERIC RECYCLED CONCRETE UNDER AXIAL LOADING

Geopolymeric recycled concrete (GRC) is a new construction material in which environmental sustainability is taken into account by using alkali solution and fly ash to completely substitute Portland cement as well as by replacing natural coarse aggregate with recycled coarse aggregate. GRC could be used together with steel hollow sections to form a composite section. This paper presents an experimental study on GRC filled tubular stub columns. A total of 12 specimens were designed, considering two section sizes of square hollow sections, different concrete types (GRC and recycled aggregate concrete, RAC) and different recycled aggregate (RA) replacement ratios of 0%, 50% and 100%. The relationship of load versus axial strain was recorded and analyzed to compare the ultimate strength and failure mechanism. Meanwhile, the ductility of the columns was investigated by a ductility index (DI). The results show that the ultimate strength decreased with the increase of RA contents for both GRC and RAC filled columns. The influence of RA content on the strength was greater in GRC than that in RAC. The effect of RA content on the ductility of the columns was further investigated. Furthermore, according to the existing code on ordinary concrete filled steel tubular columns, the load capacities of the columns in this study are calculated. The applicability of the code working on recycled concrete filled steel tubes and geopolymeric recycled concrete filled steel tubular columns is discussed.