Abstract
Recycled aggregate concrete (RAC) is an environmentally friendly building material. This paper investigates the mechanical behavior of recycled aggregate concrete filled steel tube (RACFST) columns exposed to fire. Two groups of 12 columns were designed and tested, under axial compression, before and after fire, to evaluate the degradation of bearing capacity due to fire exposure. Six specimens were subjected to axial compression tests at room temperature and the other six specimens were subjected to axial compression tests after a fire exposure. The main parameters of the specimens include the wall thickness of the steel tube (steel content) and the type of concrete materials. Several parameters as obtained from the experimental results were compared and analyzed, including the load-bearing capacity, deformation capacity, and failure characteristics of the specimens. Meanwhile, rate of loss of bearing capacity of specimens exposed to fire were calculated based on the standards EC4 and CECS28:90. The results show that concrete material has a large influence on the rate of loss of bearing capacity in the case of a relatively lower steel ratio. While steel content has little effect on the rate of loss of bearing capacity of concrete-filled steel tube (CFST) columns after fire, it has a relatively large influence on the loss rate of bearing capacity of the RACFST columns. The loss of bearing capacity of the specimens from the experiment is more serious than that from the calculation. As the calculated values are less conservative, particular attention should be given to the application of recycled aggregate concrete in actual structures.
Highlights
Recycled aggregate concrete (RAC) is a type of concrete material that is made from recycled concrete aggregate (RCA) obtained from waste concrete by cleaning, crushing, and grading [1,2].The emergence of RAC greatly reduces the demand for natural aggregate, and reduces the environmental pollution caused by construction waste [3]
In 2016, Bendimerad et al [13] studied the recycled concrete plastic shrinkage and cracking sensitivity coefficient and the results showed that replacement of fine aggregate by recycled fine aggregate has a large influence on the early age strength and cracking sensitivity of recycled aggregate concrete
The results showed that the ductility of the recycled aggregate concrete-filled steel tubular (RACFST) was still good even after the fire good even after the fire because of the constraint provided by the steel tube
Summary
Recycled aggregate concrete (RAC) is a type of concrete material that is made from recycled concrete aggregate (RCA) obtained from waste concrete by cleaning, crushing, and grading [1,2]. Sato et al [15] and Kang et al [16] Their results showed that recycled concrete can be used to cast beams if coarse aggregate replacement rate is limited to 30%; the flexural performance of recycled concrete beams and ordinary concrete beams are basically the same. Studied the axial load performance of recycled aggregate concrete-filled steel tubular short column after being subjected to high temperature, and proposed a simplified formula to calculate axial compressive bearing capacity. Chen et al [39] studied the mechanical behavior of eccentrically loaded recycled aggregate concrete-filled circular steel tube columns after being subjected to high temperature. The mechanical properties of the comprises control specimens that are subjected to axial compression test, and the other group is RACFST columns are studied at room temperature and after fire. The mechanical properties of the RACFST columns are studied at room temperature and after fire
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