Study on the mechanical behavior of circular concrete filled steel tube short columns with partially incorporated demolished concrete lumps under axial compression

With the acceleration of urbanization, a green technique for filling coarsely crushed demolished concrete lumps (DCLs) and fresh concrete (FC) into steel tubes has been developed. This study focuses on the sensitivity of factors to the axial compression behavior of circular concrete-filled steel tube (CFST) short columns with DCLs. An orthogonal design was adopted for the test. Fourteen circular CFST short columns were tested under axial loading. The diameter and length of the specimens were 219 mm and 730 mm, respectively. The diameter-to-thickness (D/t) of the specimens were 55, 73, and 109. The replacement ratios of the DCLs were 20 %, 40%, and 60%. The test results indicated that the bearing capacity of the specimen increased by 3.3% when the replacement ratio of the DCLs increased from 40% to 60%. The core concrete strength was the most sensitive factor for the bearing capacity of the short columns under axial compression, followed by D/t. The ∆0.85% optimum combination of each factor was core concrete strength = 30 MPa, D/t = 55, and replacement ratio of DCLs = 20%. This study is of significant importance for energy conservation and emission reduction, reducing solid waste emissions, protecting the environment, and conserving resources and energy.