Pullout Behavior of High-Strength Steel Fibers Embedded in Ultra-High-Performance Concrete

2012 ◽  
Vol 109 (4) ◽  

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sahar A. Mostafa ◽  
Mohamed M. EL-Deeb ◽  
Ahmed A. Farghali ◽  
A. Serag Faried

AbstractCorrosion resistance of high strength steel (HHS) embedded in ultra-high performance concrete (UHPC) immersed in 3.5% NaCl solution is evaluated in the absence and presence of nano silica (NS), nano glass waste (NGW), nano rice husk ash (NRHA) and nano metakaolin (NMK) using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) under normal and accelerated conditions. Data showed that the corrosion rate in the accelerated conditions is higher compared by the normal conditions due to the increasing in the rate of both anodic and cathodic reactions in the presence of anodic current. On the other hand, the presence of the studied nano materials decreases both the anodic and cathodic overpotentials, and shifts both the open circuit potential (Eocp) and corrosion potential (Ecorr) of HSS to more noble values, as well as decreases the values of the corrosion current densities (Icorr) in both normal and accelerated conditions. Furthermore, EIS analysis illustrates that the presence of these materials enhances both the concrete bulk resistance and the charge transfer resistance at HSS/UHPC interface, which retards the flow of the electrons between the anodic and cathodic sites, thus impeding the propagation of the corrosion process. The inhibitory effect of the studied nano materials for the corrosion of HSS is interpreted on the basis of the change in the microstructure and the compressive strength of the UHPC.







2019 ◽  
Vol 22 (8) ◽  
pp. 2006-2018 ◽  
Author(s):  
Jianan Qi ◽  
Xiaomeng Ding ◽  
Zhen Wang ◽  
Yuqing Hu

This article presents an experimental and theoretical investigation on the shear behavior of fiber-reinforced ultra-high-performance concrete beams reinforced with high-strength steel. The test parameters included the fiber volume fraction, fiber type, and stirrup ratio. The test results indicate that the shear failure in ultra-high-performance concrete beams is not brittle and catastrophic but has ductility characteristics. A moderate quantity of stirrups can significantly improve the shear behavior of ultra-high-performance concrete beams, as reflected in the thorough propagation of cracks in both shear span and pure bending zone. The depth of the compression zone considering concrete tension was derived based on the deformation compatibility and force equilibrium equations for both serviceability limit state and ultimate limit state. The comparison of the proposed method and classical beam theory shows that the concrete tension should not be neglected in the serviceability limit state analysis. After cracking, the concrete tension can be neglected for simplicity when the beam is heavily reinforced and should be considered when the beam is lightly reinforced. Then, a shear strength model was established based on Rankine’s failure criteria, the truss model, and Association Francaise de Génie Civil-Sétra. Finally, the proposed shear strength equation was verified by the test results and compared with other shear strength equations.





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