Abstract
The in situ application of recycled aggregate concrete (RAC) is of great significance in environmental protection and construction resources sustainability. However, it has been limited to nonstructural purposes due to its poor mechanical performance. External confinement using steel tubes and fiber-reinforced polymer (FRP) can significantly improve the mechanical performance of RAC and thus the first-ever study on the axial compressive behavior of glass FRP (GFRP)-confined RAC was recently reported. To have a full understanding of FRP-confined RAC, this paper has extended the type of FRP and presents a systematic experimental study on the axial compressive performance of carbon FRP (CFRP)-confined RAC. The mechanical properties of CFRP-confined RAC from the perspective of the failure mode, ultimate strength and strain, and stress–strain relationship responses were analyzed. Integrated with existing experimental data of FRP-confined RAC, the paper compiles a database for the mechanical properties of FRP-confined RAC. Based on the database, the effects of FRP type (i.e., GFRP and CFRP) and the replacement ratio of recycled coarse aggregate were investigated. The results indicated that the stress–stain behavior of FRP-confined RAC depended heavily on the unconfined concrete strength and the FRP confining pressure instead of the replacement ratio. Therefore, this study adopted eleven high-performance ultimate strength and strain models developed for FRP-confined normal aggregate concrete (NAC) to predict the mechanical properties of FRP-confined RAC. All the predictions had good agreement with the test results, which further confirmed similar roles played by FRP confinement in improving the mechanical properties of RAC and improving those of NAC. On this basis, this paper finally recommended a stress–strain relationship model for FRP-confined RAC.
Highlights
The increasing amount of waste concrete has been bringing far-reaching effects on ecological environment deterioration
Extensive research has shown that using fiber-reinforced polymer (FRP) to effectively confine concrete can significantly improve the mechanical properties of normal aggregate concrete (NAC) [2,3,4,5]
Xiao et al [49] explored the influence of the replacement ratio of recycled aggregate on the axial and eccentric compressive behaviors of glass FRP (GFRP) tube-confined recycled aggregate concrete (RAC), and the results indicated that with the increase of the replacement ratio of recycled aggregate, the peak strength of GFRP tube-confined RAC declined, accompanied by an increase in the ultimate strain
Summary
The increasing amount of waste concrete has been bringing far-reaching effects on ecological environment deterioration. The extensive studies resulted in a wide range of stress–strain relationships that developed for FRP-confined NAC [5,13,38,39,40,41,42,43,44,45,46,47,48]. Zhao et al [51] conducted the first axial compressive test on GFRP-confined RAC and observed that the replacement ratio of recycled aggregate has limited effect on the compressive behavior of GFRP-confined RAC. They compared two existing stress–strain models developed for FRP-confined NAC with their test results and concluded that these models could provide a reasonable initial approximation of the stress–strain behavior. The achievements of this paper can serve as a theoretical basis for the application of FRP to strengthen RAC structures and for the design of RAC composite structures
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