Applications of Engineering Materials

Volumes 287-290

doi: 10.4028/

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Authors: Maciej Gruszczyński
Abstract: In the paper there is presented the influence of different types of co-polymer dispersion additives onto the magnitude of shrinkage and strength properties of cement composites. The effect of application of such additives was compared and confronted with the action of widely used classical admixture reducing shrinkage based on multi-molecular alcohol (propylene alcohol). As a result of conducted tests the significant reduction in shrinkage strains and increase in bending strength was observed due to the application of co-polymer dispersion with the amount of at least 5% of the cement mass. Reduction of shrinkage and improvement of serviceability properties to great extent prejudge the technical attractiveness of co-polymer and cement materials for the cases of concrete structures repairs and constructing industrial floors without joints.
Authors: Mei Li, Jia Hui Peng, Ting Jian Ning
Abstract: Influence factors of co-crystallized (lattice) P2O5 were investigated from the dihydrate process conditions and aimed to optimize the process conditions and reduce the co-crystallized (lattice) P2O5 content in phosphogypsum. It is found that: 1) reaction temperature, P2O5 concentration in liquid phase and SO3 concentration in liquid phase are main factors influencing the content of co-crystallized (lattice) P2O5; 2) increasing the reaction temperature, can reduce the supersaturation ratio of the crystallization, decrease the solution viscosity, which help ions diffusion and reduce the content of co-crystallized (lattice) P2O5; 3) improvement of SO3 concentration in liquid phase can increase the collision probability between calcium sulfate lattice and SO42-, reduce the Ca2+ concentration and prevent the dissociation of phosphoric acid, so HPO42- concentration does not increase, thereby reducing content of co-crystallized (lattice) P2O5; 4) increasing the P2O5 concentration in liquid phase will lead to a corresponding increase of the HPO42- concentration, solution viscosity increasing, diffusion problems, and deterioration of crystallization conditions, which increased the content of co-crystallized (lattice) P2O5; 5) the formation mechanism of co-crystallized (lattice) P2O5 is: any changes in the reaction system whatever can make the local concentration or average concentration of Ca2+ and HPO42- in the solution increased, will increase the probability of the formation of co-crystallized (lattice) P2O5.
Authors: Yun Xia Zhang, Jun Jie Hao, Jun Ting Qi
Abstract: In this paper, the effect of Nb2O5 on the microstructure and dielectric properties of BaTiO3-based ceramics has been investigated. In the study,Nb2O5 is added to the BaTiO3-based ferroelectric material by conventional solid state synthesis. The structure is identified by X-ray diffraction method and SEM is also employed to observe the surface morphologies of the sample. The specimens of the ferroelectric doped with 2wt% Nb2O5 sintered at 1260°C for 1h exhibit attractive properties, its dielectric temperature coefficient is lower than 15% over a wide temperature range from -55 to +180°C.
Authors: Jun Hong Zhang
Abstract: In order to reduce the coke consumption of Blast Furnace(BF),a relevance analysis is carried out for operation parameters and fuel rate of BF,and a prediction method that is combining clustering analysis and artificial neural network for coke rate is proposed. The data cluster is divided into several classes by clustering analysis,the data similarity is high,and the neural network model is used to realize the prediction of coke rate. By combining the neural network with clustering analysis,the data in one BF is simulated,and the results are compared with the traditional neural network model. The result shows that the improved neural network has a higher accuracy, the average absolute error can be decreased by 3.13kg/t, and the average relative error can be decreased by 5.19%, it will have a good using foreground.
Authors: Xiao Xin Feng, Xiu Juan Li, Qing Min Wei
Abstract: C-S-H gel was prepared by extracting from the hardened cement paste, and was immersed in Na2SO4 solution and MgSO4 solution respectively. The microstructure of the C-S-H gel attacked by sulphate was observed by means of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. It is found that C-S-H gel is attacked by both Na2SO4 and MgSO4, and gypsum forms whether in low or high concentration solution of Na2SO4 and MgSO4.
Authors: Jing Hai Yu, Qiong Sun
Abstract: Based on the experimental investigation of quasi-static test of 6 pieces of the AAC block walls, the failure features of the AAC block wall are studied and analyzed, failure features and shear strength of the walls due to different height to width ratio and vertical pressing stress are also studied. The results indicate :1) the failure process and characteristics of the walls were basically the same,firstly produced the Shear inclined cracks in the central of the wall,then formed the main cross inclined crack and some secondary cracks.2)The failure feature belonged to the shear failure, the height to width ratio and vertical pressing stress have great influence on the failure feature of AAC load bearing block wall.
Authors: Yan Yao, Hao Wu, Ling Wang
Abstract: Interfacial transition zone (ITZ) is the weakest part in concrete structure because of the interrelation between its special characters and the performance of concrete, and adding mineral admixture in concrete is a feasible and effective way to improve ITZ. The workability, mechanical and durability performance of filling materials with Fly ash and Coal gangue has been invesitgated, and the interrelation has been research in a micro view by means of SEM and EDS.
Authors: Hong Chang Qu, Chang Qing Wu, Ling Ling Chen
Abstract: In this paper, different types of debonding failure modes are described. Study of concrete cracking behavior and interfacial debonding fracture in fiber reinforced polymer (FRP)-strengthened concrete beams are carried out. A finite element analysis is performed to investigate the different types of debonding propagation along FRP–concrete interface and crack distribution in concrete. The proposed FE, denoted as FRP–FB (force-based) beam, is used to predict the load-carrying capacity and the applied load-midspan deflection response of RC beams subjected to four-point bending loading. Numerical simulations and experimental measurements are compared based on numerous tests available in the literatures and published by different authors. The numerically simulated responses agree remarkably well with the corresponding experimental results. It demonstrates that the proposed two-dimensional frame finite element (FE) is able to accurately estimate the load-carrying capacity of reinforced concrete (RC) beams flexurally strengthened with externally bonded fibre reinforced polymer (FRP) strips and plates.
Authors: Li Xin Tan, Shao Long Huang, Ji Yu Han, Qing Jun Ding
Abstract: In this article, research on hydration mechanism of 50% Portland cement–50% fly ash(FA) systems has been carried out with TAM AIR Isothermal Calorimete (TA) and 29Si nuclear magnetic resonance(NMR) spectroscopy. The research was including hydration heat liberation behavior and nanostructure of C-S-H gel in hydrated cement systems. The addition of fly ash could observably reduce the total hydration heat and the mean chain length (MCL) of C-S-H gel was found to be and respectively for 7-day-old and 28-day-old.
Authors: Zhan Ying Guo, Gang Zhao, Yue Liu, Ni Tian
Abstract: The number and size of the precipitation of spherical Al3Zr particles, in aluminium alloy containing trace of Zr which subjected to different heat treatments, have been investigated by transmission electron microscopy. The results show that, the number of spherical Al3Zr particles is determined by the pretreatment, and that the size is determined by the homogenization. The number of spherical Al3Zr particles increases with prolonging the time of pretreatment between 0h to 48h and rising the temperature of pretreatment between 200°C to 400°C, and the size of spherical Al3Zr particles turn out to be the same. The size of spherical Al3Zr particles increases with prolonging the time of homogenization between 0h to 48h and rising the temperature of homogenization between 470°C to 500°C.

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