Experimental and theoretical analysis of steel tubed geopolymer concrete columns under axial compression.

To alleviate the consumption of resources and promote the further application of geopolymer concrete in practical engineering, the mechanical performance of steel tubed geopolymer concrete (STGC) columns under axial compression was first explored in this study. The impact of experimental parameters including concrete types, configurations of steel tubes, diameter-to-thickness ratios (D / t), and slag contents were analyzed in detail. The test results illustrate that after grooving at the two ends of columns, the axial deformation of the external steel tube becomes smaller compared with the core concrete and the confining pressure of the external steel tube is improved significantly, resulting in a remarkable improvement of the compressive strength and corresponding strain at both peak and residual state of the specimens. Although little influence of concrete types on the steel stress evaluation is detected, the ductility of the STGC columns is inferior to that of the specimens with ordinary concrete due to the obvious brittle property of geopolymer concrete. Moreover, the ratio of axial stress to yield strength of the external steel tube at the peak load of STGC columns is increased with the decrease of diameter-to-thickness ratio and concrete strength. Finally, a new model for predicting the steel axial stress in steel tubed concrete (STC) columns at the peak state is established and a load capacity model incorporating the steel axial contribution is also developed for STC columns. Compared with extensive existing test results, the developed model can provide satisfactory accuracy. • Axial compressive behavior of steel tubed geopolymer concrete columns was investigated. • Effects of key test parameters on the interaction mechanism of the composite columns were analyzed. • The axial stress model of steel tube at the peak state of STC columns is proposed. • The load capacity model incorporating the axial contribution of the steel tube is developed for STC columns. [ABSTRACT FROM AUTHOR]