Rebar free high performance ductile concrete beams powered by CFRP and post-tensioning

The present study investigates the flexural capacity of high-performance ductile concrete (HPDC) beams, with a focus on their reliability for large-scale applications. Due to the high fiber volume fraction in the HPDC mixture, a very low reinforcement ratio (almost negligible) was employed to address challenges related to fiber congestion in areas with heavy steel reinforcement. To compensate for this low ratio, various strengthening techniques were evaluated on ten large-scale HPDC beams, including differing configurations of carbon fiber-reinforced polymer (CFRP) sheets and post-tensioning methods. The primary parameters assessed included ultimate flexural capacity, ductility ratio, absorbed energy, stiffness, first cracking load, and maximum deflection, alongside reference specimens for comparative analysis. The results indicated that while the reference beam exhibited sufficient flexural capacity to meet the minimum requirements outlined in the design codes, it displayed an inappropriate cracking pattern and low absorbed energy. Conversely, the application of strengthening methods resulted in a significant enhancement of flexural capacity, a considerable reduction in the width of failure cracks, and an increase in the number of small cracks. Overall, the findings of this study demonstrate that HPDC beams, when reinforced with strengthening techniques, can effectively function as structural members even with minimal reinforcement.