Compressive Behaviors Of CFRP-confined Recycled Aggregate Concrete Cylinders

Recycled concrete aggregate (RCA) can be re-used to partially or totally substitute natural aggregates in concrete and the concrete with RCA is normally called recycled aggregate concrete (RAC). In the past decade, the research on RAC has been a world-wide interest, due to the social, environmental and potential economic significance of reusing RCA. However, to date, the application of RAC has been mainly limited to non-structural concretes, due to the lower density, lower strength and stiffness, larger creep and shrinkage and less durability compared to natural aggregate concrete (NAC). Fiber reinforced polymer (FRP) composites have found increasingly wide applications in civil engineering due to their salient advantages such as high strength-to-weight ratio and high resistance to corrosion and fatigue loading. One important application of FRP composites in construction is used as FRP jackets to confine columns to enhance their load carrying capacity and ductility. Against the above background, this thesis presents an experimental study on the compressive behaviors of CFRP-confined RAC cylinders. The idea of using FRP to confine RAC is mainly to reduce/diminish the weaknesses (e.g. lower strength, less durability) of RAC and to increase its durability by making use of the disvanateges of FRP. In the present study, the effects of two major parameters, namely the replacement percentage of RCA (0%,25%,50%,75%, 100%) and the thickness of CFRP (0.111mm,0.167mm,0.222mm,0.333mm,0.5mm) on the compressive behaviors, including failure mode, elastic modulus, stress-strain behavior, dilation properties, and ultimate conditions, were investigated. Furthurmore, of the predcitons from an analysis-oriented model and a design-oriented model and the experimental results are compared and discussed. It can be concluded from the test results that with the FRP confinement, both the axial compression strength and ductility of RAC can be obviously improved; the ultimate axial strain of the FRP-confined RAC is also significantly increased. The comparsions showed that and the confining effect of CFRP on RAC is comparable with CFRP confined NAC, implying that the main disadvantages of RAC (e.g. lower strength, less durability) can be largely diminished in FRP confined-RAC. The results presented in this studyemonstrate the possibilities for the reliable and extensive use of RAC in building construction. The outcome of this study is thus of great research significance and application merit.