javad sabzi

The present study investigates the properties of cementitious mortars in which different portions of cement were replaced with mineral materials including electric arc furnace dust (EAFD), red mud (RM), marble powder (MP), and glass powder (GP). Compressive strength at ages of 7, 28, and 90 days, tensile strength at ages of 7 and 28 days, water absorption with durations of 30 minutes, 24 hours, and 72 hours after 90 days of curing, and chemical resistance against sulfuric acid tests were carried out on hardened specimens cured for 28 days. The results show that replacing 15% of cement with marble powder significantly increased the compressive strength of specimens cured for 7, 28, and 90 days. Furthermore, replacing cement with 5 and 15% glass powder or 5% of red mud increased the tensile strength. In order to investigate the performance of the repair mortars, one of them was chosen for strengthening RC beams. Three RC beams were manufactured and tested through 4-point bending scheme. The results indicate that the load-carrying capacity of the strengthened beam by CFRP sheet and repair mortar was the same as the specimen strengthened by CFRP sheet and epoxy resin, and was 60% higher than that of un-strengthened specimen.

The present study aims to compare the flexural behavior of reinforced concrete (RC) beams strengthened by fiber reinforced polymer (FRP) with that of fiber reinforced cementitious matrix (FRCM) sheets. Accordingly, 6 RC beams were manufactured and strengthened by FRP and FRCM. Other parameters such as strengthening method and tensile reinforcement ratio were investigated. The results show that in externally bonded reinforcement (EBR) method, strengthening by FRCM sheets leads to the improvement of load carrying capacity by 12.8% and 16.8%, respectively, in specimens with and compared to the specimens strengthened by FRP sheets. Furthermore, the failure mode of specimens strengthened by EBR method was debonding in case of FRP sheets while the failure mode of FRCM strengthened specimens was fiber rupture. In externally bonded reinforcement on grooves (EBROG) method, the load carrying capacity of specimens strengthened by FRP and FRCM was almost the same, while their failure mode was debonding with partial cover separation and complete cover separation. Finally, the experimental results were compared to the existing models and different code provisions. It was observed that by increasing the tensile reinforcement ratio in FRP strengthened beams, the predicted results by analytical models become closer to the experimental results.

Re-centering is an exclusive characteristic of superelastic Shape Memory Alloys (SMAs) which can be used in manufacturing and retrofitting of reinforced concrete elements. Reinforced concrete beams retrofitted with SMA bars have more ductility and higher energy dissipation compared to conventional RC beams. Furthermore, these beams experience less damage in consecutive loading-unloading cycles. The current research aims to investigate the behavior of reinforced concrete beams retrofitted with SMA bars using Near-Surface Mounted (NSM) flexural retrofitting method. Eleven RC beam specimens with the cross section of 200*150 mm and length of 1150 mm were cast. Three of the specimens had no external strengthening, four of them were retrofitted with SMA bars and other four beams were retrofitted with GFRP reinforcements. The specimens were subjected to three-point bending test under either monastic or loading-unloading. Different parameters including load-carrying capacity, energy dissipation, deformation recovery and reduction capability of crack width were investigated. The results showed that RC beams retrofitted with SMA bars had more mid-span deflection and higher energy dissipation compared to other specimens under monotonic loading. Moreover, under loading-unloading, RC beams retrofitted with SMA bars method experienced less damage.