- S. Mardi, and M. Bastami. “Cyclic Performance of High Strength Concrete Beams Reinforced with Hexagonal Wire Mesh.” Engineering Structures (ready for submission.)
The brittle behavior of high strength concrete (HSC) has limited its use in ductile structural elements. The target of the following research is based on developing a novel reinforcing techniques using hexagonal wire mesh (HWM) as an inner jacket to improve the seismic response of reinforced high strength self-compacting concrete (RHSSCC) beams and achieving a ductile behavior. By conducting rheological tests and finding the desired mixture for control specimen, results of the elastic modulus, compressive and tensile strength of 300 x 150 mm (12 x 6 in.) concrete cylinder reinforced with HWM are investigated. Furthermore, the effects of HWM on RC beams are evaluated in the form of single and two layers’ jackets under cyclic loading condition by testing conventional RC beams reinforced with HWM with different mesh opening size and wire diameter. The use of HWM increased loading capacity, ductility and the number of the applied load cycles. Redistribution of cracks and extra utilization of unused beam capacity were revealed by studying crack propagation. Afterward, beams with the fewer shear reinforcement were tested and it was indicated that stirrups could be largely replaced by HWM. Eventually, it was evaluated that using HWM is cost-effective by conducting an economic analysis.
M. Aziminezhad, S. Mardi, P. Hajikarimi, F. M. Nejad, A. H. Gandomi. “Loading Rate Effect on Fracture Behavior of Fiber Reinforced High-Strength Concrete Using Semi-Circular Bending Test.” Construction and Building materials (under review).
Abstract: Adding different types of fiber is one of the most common ways to enhance high strength concrete’s mechanical behavior. In this paper, the effect of loading rate and different type of fibers including glass, polypropylene, and steel were studied implementing semi-circular bending (SCB) test method. It was evaluated that the SCB test can be used as a rapid and simple method to measure fracture properties of fiber reinforced high strength concrete (HSC) including ductility, energy absorption, and loading capacity by considering the effect of loading rate on the parameters mentioned above. Specimens with glass fibers had shown the most ductile behavior among all specimens with different types of fiber. On the other hand, steel fibers provided higher strength and higher energy absorption for the specimens. While specimens with steel fibers are highly sensitive to loading rate in terms of peak load, this effect is not significant for specimens with glass and polypropylene fibers.
- M. Aziminezhad, S. Mardi, P. Hajikarimi, and F. M. Nejad. “Energy-Based Method for Evaluating Cracks and Resistance of Fiber Reinforced Ultra-High Strength Concrete under Impact Loads.” AUT Journal of Civil Engineering, Accepted in August 2019 (In Press)
Abstract: In order to adjust the lack of sufficient ductility of ultra-high strength concrete (UHSC), different types of fiber were used in this study. This research investigates the effect of glass, polypropylene and steel fibers on the impact resistance and crack propagation of fiber reinforced UHSCs by implementing slab specimens with a dimension of 300×300×30 mm. The experimental program includes 18 specimens with 1%, 1.5% and 2% of concrete volume for each type of fiber which was made with two different mixing methods (Ordinary fiber reinforced concrete (FRC) and high performance fiber reinforced concrete (HPFRC)). In this study, specimens were placed under a low-velocity impact loading (5.42 m/s) within a fixed rigid constrained setup. The health index and the crack propagation correlation are two criteria for determining the trend of degradation and impact resistance reduction. Results demonstrate that the FRCs show higher impact resistance in comparison with the HPFRC because the HPFRC method doesn’t provide enough cohesion between concrete and fibers. The obtained results also show that FRC specimens include polypropylene, endure higher impact resistance with a greater amount of health index rather than other specimens. By increasing the fiber’s volume in the specimens fabricated with glass and polypropylene, a more homogenous composite was formed and energy spread more uniform over all faces of FRC specimen.
- S. Mardi, and M. Bastami. “Developing a Cost-Effective Approach for Enhancing the Rheological and Mechanical Behavior of High Strength Self-Compacting Concrete.” Journal of Structural Engineering and Geo-Techniques 8, no. 1 (2018): 41–54.
Abstract: Despite the numerous advantages of using concrete with high strength capacity, the brittle behavior of high strength concrete (HSC) and higher production cost has limited its use in the construction industry. This research aims to develop a cost-effective approach for production of high strength self-compacting concrete with desirable performance in either compressive or tensile loading condition. To reach this purpose, 18 mixtures were cast initially with different w/c, binder, and silica-fume percentages. The results show that it is possible to produce high strength self-compacting concrete economically without using any additives such as silica-fume. Afterward, an innovative reinforcing technique using hexagonal wire mesh (HWM) were introduced for enhancing the HSC performance. The results show that HWM is able to enhance HSC behavior in both tensile and compressive loading condition. Finally, an economic analysis was conducted and the optimum HWM properties are selected according to the analysis results.
COI code: JR_QSEJ-8-1_004