08.22: Axially compressive behaviours of steel tubes filled with post‐pouring concrete and precast segments containing DCLs and FC

Abstract

ABSTRACTTo improve the construction efficiency of steel tubes filled with demolished concrete lumps (DCLs) and fresh concrete (FC) at construction site, a new fabrication method is proposed in this paper, and the axially compressive behaviours of four columns prepared using this method have been experimentally investigated and compared with those of the control column. According to the proposed fabrication method, the segments containing DCLs and FC are precast first, and then are placed into the steel tube. Finally, post‐pouring concrete is employed to fill the space between the steel tube and precast segments. In this way, the processing of DCLs is not involved at the construction site, and thus the efficiency of construction can be enhanced significantly. The parameters considered in the compressive tests included the number of the precast segments in the steel tube (S1=one segment, S2=two segments, and S3=three segments), and the cross‐sectional dimensions of the precast segment (C1=331 mm×331 mm, and C2=303 mm×303 mm). The outer diameter and thickness of the steel tubes were, respectively, 500 mm and 5.7 mm. The 150 mm cubic compressive strength of the post‐pouring concrete was 32.8 MPa. The replacement ratio of DCLs in the precast segments was 40%, and the 150 mm cubic compressive strengths of the demolished concrete and fresh concrete used in the precast segments were 31.5 MPa and 47.4 MPa, respectively. The control column was a steel tube filled with DCLs and the post‐pouring concrete simultaneously. The five columns had the same height as 1800 mm, and the weight of DCLs adopted in the control column was the same as that employed in other four columns. In this paper, failure patterns of the five specimens are presented, and influences of the aforementioned parameters on the specimens’ axially compressive behaviours have been discussed. It is found that the columns prepared using the new fabrication method have similar failure modes as compared with the control column, and the number and sectional size of the precast segments have different impacts on the column's axially compressive performance.