Experimental study on strength and ductility of steel tubular stub columns filled with Geopolymeric Recycled Concrete

Geopolymeric Recycled Concrete (GRC) is a new construction material which takes environmental sustainability 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 composite section. There is very limited study on such GRC filled tubular sections. This paper presents an experimental study on GRC filled tubular stub columns. A total of 12 specimens were tested. The main parameters varied in the tests are: (1) two section sizes of square hollow sections (Bxt) with 200 mm x 6 mm and 150 mm x 5 mm; (2) different concrete types: GRC and Recycled Aggregate Concrete (RAC); (3) different Recycled Aggregate (RA) replacement ratios of 0%, 50% and 100%. The relationship of load versus axial strain was recorded and analysed 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 increasing 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. Simulation method for predicting load versus strain relationship is discussed for RAC and GRC filled steel tubular columns with different RA replacement ratios.