Experimental study and prediction model analysis for creep behaviour of recycled ceramic aggregate concrete-filled square-shaped steel tube

Abstract

The coarse aggregate formed by crushing waste ceramics is used to produce recycled ceramic coarse aggregate concrete (RCCAC), which is then poured into steel tubes, resulting in a recycled ceramic aggregate concrete-filled steel tube (RCCACFST). The restraining effect of the steel tube can compensate for deficiencies in both the material properties and the interface performance. Concrete creep is a well-known factor that affects the mechanical properties of CFST structures. Therefore, this paper presents a creep test, scanning electron microscopy (SEM) and calculation analysis for RCCACFST, and some valuable data and innovative results were obtained. Firstly, the creep tests of six square RCCACFST short columns were carried out under different stress levels and recycled ceramic coarse aggregate (RCCA) replacement rate. The test results demonstrated that the incorporation of RCCA reduced the creep coefficient of the composite columns by 7.4 %–18.8 %. Nonlinear creep development was evident when the stress level in the core concrete exceeded 0.49. Furthermore, SEM analysis showed that the constraint performance of the RCCA on the cement matrix was weaker than that of the natural aggregate. The experimental data were then compared with predictions made using the age-adjusted effective modulus method (AAEM). The ACI209-W and Ruiz-ACI209-W models were recommended for predicting the long-term deformation of RCCACFST under low and high loading levels, respectively. Finally, the influence of 5 key parameters on RCCACFST creep was studied. The results can be used as reference for the full-life cycle design of RCCACFST.