Papers by Keyword: SCC

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Authors: Zhong Bing Chen, Yu Hui Chen, Bo Yan Li, Xiao Yun Zeng, Yi Shi Lv, Xiao Liu
Abstract: Corrosion type, reasons and influential factors of the tail heated surface tube of the low carbon steel under the flue gas medium in LNG(Liquefied Natural Gas) power station HRSG(Heat Recovery Steam Generator) were researched through cracks morphology observation, corrosion products analysis, corrosion elements measurement and tube wall temperature field FEM calculation. Results showed that the crack initiated from the outer wall of the tube and propagated toward the inner wall with the arborescent morphology. Intergranular embrittlement ruptured. Rock type feature and secondary crack were observed on the fracture. Mud pattern and polygonal figure of the corrosion products were present. According to these morphology characteristics, the crack was identified as stress corrosion crack, and corrosion type was SCC(Stress Corrosion Cracking). Reasons of SCC were that low feed water or flue gas temperature during a certain period of the unit startup and shutdown for peaking operation brought about the temperature of the outer wall of tube below the flue gas dew point, and the flue gas became dew and corrosion solution emerged on the outer wall of tube. The SCC component was CO2 solution according to the corrosion products. S and Cl elements were found in the outer wall of tube, but their effects on SCC are still needed more researches.
Authors: Zhi Ying Wang, Jian Qiu Wang, En Hou Han, Wei Ke
Abstract: The effect of applied potential on the stress corrosion cracking (SCC) initiation of X-70 pipeline steel in near-neutral pH solution has been investigated by using a slow strain rate testing (SSRT) apparatus and electric potential drop (EPD) method. It was found from the SSRT results that the initiation stress decreased with the decrease in the potential from -790mVSCE to -950mVSCE. But the initiation stress increased when the applied potential was at -1100mVSCE and then decreased at -1200mVSCE. The initiation stress also decreased when the anodic potentials were applied to the samples. SEM observations favored the above SSRT results.
Authors: Hai Peng Gu, Gu Hua Li, Xiao Hui Zeng, Jian Qiang Cheng
Abstract: In order to prepare SCC (self-compacting concrete) which is used as the packing layer in CRTS III type track system this paper primary researched the influence of sand ratio on its performance through experiments of the design of mix proportion. Test results show that when sand ratio is too small, the fluidity of SCC will be bad and the concrete will generate segregation and weeping. If sand ratio is too great, the workability of SCC will not be good either, but segregation will not occur again. The optimum range of sand ratio is 0.56 to 0.58 in this paper, while the range proposed by China Academy of Railway Sciences is 0.50 to 0.55.
Authors: Vijay Anand, Janardhana Maganti, Azmi Ibrahim, K.U. Muthu
Abstract: Self-compacting concrete has been accepted as a quality product. A Suitable method for estimating the instantaneous deflection for SFRSCC is not available. In this study an effective moment of inertia function has been formulated with a power coefficient obtained from authors and others data. The proposed method is found to predict the instantaneous deflections satisfactorily.
Authors: Ying Wang, Xiao Yu Wang, Jin Hua Xu
Abstract: Self-compacting concrete (SCC) is employed to construct a new CFT column-CFT beam frame structure in this research. In order to further assess filling result of SCC in the long steel tube to ensure good compaction rate, a 1/4 scale column-beam subassembly made of acrylics tube and concrete visual model, in which fresh concrete is simulated through mortar phase and coarse aggregate phase, are adopted to do the simulation experiment work. The experiment result shows that good filling result is able to be obtained inside the subassembly which indicates that the new CFT column-CFT beam frame structure is possible to be constructed in the real building.
Authors: Xian Lei Wu, Jian Jun Shi, Zhi Shan
Abstract: This template is mainly about the analysis of mechanical property of SCC in a flow state in the V-Funnel. It aims to establish the testing formula of rheological constants by Engineering Fluid Mechanics, which can provide academic basis for V-Funnel test of SCC properties. MATLAB image process technique was introduced in the process which can greatly improve its precision and reliability. It can also provide a new train of thought to experimental data.
Authors: Cheng Kuo Lee, Chung Sheng Chang, An Hung Tan, Ching Yi Yang, Sheng Long Lee
Abstract: In this study nanoTiO2 particles were incorporated into the electroless plating solution to prepare Ni-P-TiO2 composite coating on anodized AA7075 aluminum alloy to improve the wear and stress corrosion cracking resistance of the coated alloy in 3.5%NaCl solution. The anodized AA7075 aluminum alloy was also performed by a boiling water sealing treatment for comparison. The wear and stress corrosion cracking (SCC) characteristics were investigated using a self-designed block-on-ring machine and slow strain rate test. The effect of corrosion was evaluated by electrochemical polarization measurements. The surface morphology, element composition and surface hardness of the coating were analyzed by scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDS) and Vicker′s hardness tester. Experimental results indicated that after boiling water sealing treatment the resistance properties of the anodized AA7075 aluminum alloy were further improved. The anodizing treatment of AA7075 aluminum alloy gave a thick film with high porosity. The porous film efficiently improved the cohesion, adhesion and hardness of the electroless Ni-P composite coating. Therefore, the electroless Ni-P composite coating deposited on the anodized AA7075 aluminum alloy offered a superior wear, pitting corrosion and stress corrosion cracking resistance properties than both anodizing and sealing treatment. By comparison with Ni-P and Ni-P-TiO2 coatings the incorporation of TiO2 resulted in a more uniform and crack-free surface structure of the composite coating. This is responsible for the higher hardness, better wear, pitting corrosion and stress corrosion cracking resistance of the electroless Ni-P-TiO2 coating.
Authors: Abdelkader Mebrouki, Nasr Eddine Bouhamou, Fouzia Mostefa
Abstract: Concrete is composed of a liquid phase (paste) and of a solid phase (aggregates with fixed gravel/sand ratio), the concrete self-compacting properties come necessarily from those of the paste. The present research is the continuity of a first phase of the testing already conducted, which resulted in obtaining an optimal self-compacting cement paste composition. This paste will be used to prepare a self-compacting concrete (SCC), while passing from the scale of the cement paste to that of the concrete, by injecting wet aggregate to the self-compacting paste. The excess paste theory was used to determine the thickness of the paste coating each aggregate with a given diameter of constituting granular skeleton, then generalized for the determination of the quantity of total paste allowing the flow of the concrete by decreasing frictions between the grains of its granular skeleton. This approach was also experimentally validated. The influence of the granular distribution was minimized by the use of the approach based on the determination of the average diameter of the aggregates. This required the determination of a homothetic factor “K” similar for all concretes with different aggregate grading. Formulation of a self-compacting concrete passes initially by the determination of a sufficient quantity of paste allowing its flow without frictions between its aggregates and to balance the mixture by the quantity of water retained by the aggregates. The self-compacting concrete characteristics would come from those of the cement paste which composes it.
Authors: Gladys Patricia Abdel Rahim, Jairo Arbey Rodríguez
Abstract: We study the structural and electronic properties of scandium carbide ScC and niobium carbide NbC in both the sodium chloride rock salt (NaCl) and wurtzite structures by means of accurate first principles total energy calculations. The calculations were performed employing the full-potential linearized plane wave method (FP-LAPW). We used the generalized gradient approximation (GGA) of Perdew Burke and Ernzerhof for the exchange and correlation potential. Volume optimization and density of states including spin (DOS) of the systems are presented.
Authors: Dragica Jevtić, Dimitrije Zakić, Aleksandar Savić, Veis Šerifi
Abstract: Applications of fly ash in building industry have very important and relevant problems of origin which are discussed in this paper. Authors have performed tests on mortar, plain concrete and Self Compacting Concrete (SCC) specimens. Experiments showed satisfactory results concerning possible application of fly ash as admixture for cementitious composites. Experimental research was conducted in the Laboratory for materials at the Faculty of Civil Engineering, University of Belgrade.
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