Parametric Study of Reinforced Concrete Columns Embedded with PET Bottles Under Compression

This study presents finite element investigations on the use of polyethylene terephthalate (PET) bottles as void formers in reinforced concrete columns subjected to pure axial compression. The incorporation of PET bottles in reinforced concrete structures reduces concrete consumption while also providing a sustainable disposal solution for used PET bottles. In addition, for the same amount of concrete used in equivalent solid and voided columns, the voided column can exhibit greater flexural capacity due to the increased moment arm of the longitudinal reinforcement. In this study, a finite element-based parametric study is conducted on reinforced concrete columns containing voids within the core. The model was validated using the results of an experimental testing program consisting of 16 scaled reinforced concrete columns, of which 8 specimens had solid cross-sections and 8 specimens had hollow cross-sections. The numerical study considered variations in the longitudinal reinforcement ratio, tie spacing, concrete compressive strength and shape of cross-section. The finite element analyses were conducted using ABAQUS with consideration of material nonlinearity, and the results showed good agreement with the experimental findings. Furthermore, a parametric study was performed to quantify the effects of concrete compressive strength, longitudinal and transverse reinforcement ratios, void diameter, and column cross-sectional dimensions on the load-carrying capacity, ductility, stiffness, and residual strength of the columns. The findings of the study demonstrated that introducing voids formed by tightly stacked PET bottles within the core of reinforced concrete tied columns does not adversely affect their structural behavior under axial compressive loading, as the response of the voided columns was found to be comparable to that of their solid counterparts. The parametric study demonstrated that concrete compressive strength and longitudinal reinforcement ratio significantly influenced the load-carrying capacity and stiffness of voided columns, whereas tie spacing and void diameter had comparatively moderate effects, and changing the column shape while maintaining the same cross-sectional area as the equivalent solid section had negligible influence on the overall structural performance.