Experimental Study on Axial Compressive Behavior of Reinforced Recycled Aggregate Concrete-Filled Steel Tube Short Column

To investigate the improving effect of reinforcement on the loading performance of recycled concrete-filled circular steel tube (RACFST) columns with 100% replacement-ratio of recycled coarse aggregate, axial compression tests of reinforced RACFST (R-RACFST) with varying longitudinal reinforcement ratio were conducted. The comparative analysis results on key mechanical indices, such as failure mode, load-displacement curve, stiffness, yield-to-strength ratio and the composite effect, showed that the reinforcement could effectively mitigate the brittleness of recycled concrete core, and improved the peak load and the after-peak plastic deformation capacity, and relieved the degradation in stiffness; as far as the yield-to-strength ratio and composite effect are concerned, larger ratio of reinforcement not necessarily brought larger increase in performance, namely in a proper range of ratio, reinforcement would bring better composite effect, and could better utilize the reinforcement. As results, configuring a little amount of reinforcement would put the R-RACFST member with 100% replacement-ratio of recycled coarse aggregate into better mechanical performance, and hereby make it possible to use recycled coarse aggregate 100%; a proper range of reinforcement ratio was recommended as 0.84%-3.9%; the proposed equation for predicting the ultimate load bearing capacity of R-RACFST was stable and reliable.