Papers by Keyword: Thixotropy

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Authors: Hiroshi Nemoto, Shigeyuki Date, Shinchiro Hashimoto
Abstract: Long-distance pumping of concrete (up to 2000 m, with relay pumps installed at two locations) was carried out for placing invert concrete at a caisson—the construction site of a spillway discharge section. After quantifying the required performance and determining of the mix proportions of the invert concrete that would be used in the long-distance pumping, the authors focused on thixotropy as a factor that affects the pumping load. Through laboratory tests and using AE and a high-range water reducing agent with high dispersion effect, retention and pumpability enhancing admixture were found to be effective in reducing thixotropy.
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Authors: Yasuhiro Uetani, H. Takagi, Tomokazu Yamashita, Kenji Matsuda, Susumu Ikeno
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Authors: Hui Chen, Jian Ming Yang, Jia Wei Zheng
Abstract: This article mainly aims at to research the affect of thixotropy on the development of the formwork lateral pressure, the ultimate goal is to minimize the potential safety hazard of construction.Before the experiment, through the tests of net cement slurry, we can determine kaolin (additive) to change the influence of the liquidity of concrete. For the mixture of self-compacting concrete (SCC) ,set different content of admixture. Through experimental simulation measurement in 4 meters height of concrete pouring and pouring diameter of 150 mm, test the size of the lateral pressure casting the bottom template, and compare the condition of not using mineral admixtures, helps to identify the most appropriate for the amount of admixture.
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Authors: Kenji Miwa, Rudi S. Rachmat, Takuya Tamura
Abstract: We have developed new type semi-solid injection process, that is, runner-less injection process. In order to investigate the effects of solid fraction on microstructure and casting defects of AZ91D in new type semi solid injection process, semi-solid forming testing machine which has the same system as a runner-less injection machine has been made on an experimental basis. Its temperature controlling system has been established to obtain the homogeneous solid-liquid coexisted state in its injection cylinder. AZ91D billets are injected into a permanent mold by this machine in the semi-solid state. A shearing in the part of nozzle of injection cylinder is the most important to reveal thixotropic property of alloy slurry in semi solid forming process by injection machine. So it needs controlling of solid fraction to affect thixotropic property. In order to decrease casting defects and hold homogeneous structure, solid fraction more over 50% is needed. But when the solid fraction increases more than 50%, primary solid particles grow coarser, and then controlling method is required to suppress coarsening. In the case of less than 50% of solid fraction, liquid part preferentially fills inside the permanent mold and alloy slurry continue to fill the mold behind alloy liquid. Then large casting defects form at the boundary of both flows.
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Authors: Cong Li, Qi Cheng Liu, An Ming Chen, Jun Feng, Tao Feng
Abstract: This paper aims at solving the poor rheology of clay-water- acid-resistant overglaze slip. Natronite, tripolyphosphate sodium and composite deflocculant compounded of sodium natronite and sodium tripolyphosphate in proportion of 1:2 respectively were taken as deflocculants, and single-factor test and ring test were used to measure the variations in zeta-potential, viscosity and thixotropic. The results show that 0.3% of the composite deflocculants are better than any other single deflocculants on clay-water-acid-resistant overglaze slip, which has a better liquidity, a better thixotropy and a better stability that can avoid defects on glaze such as crawling, pinhole, hard spot, focal spot. Some factual and theoretic bases can be provided for enamel industry.
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Authors: Li Ping Guo, Lei Wang, Yi Min Zhang
Abstract: Thixotropy, which is an important rheological behavior of waxy crudes, is very important to the hydraulic characteristics and safety of the restart process of crude oil pipelines. Thixotropic behaviors of four waxy crudes were studied experimentally under three kinds of loading conditions, which were constant shear rate, stepwise increase of shear rate and cyclic change of shear rate, namely hysteresis loop. Eight thixotropic models were evaluated by least-square regressions based on experimental data. The average absolute deviation was taken as the measurement of fitness of a model. It is concluded that the model, which was established on the basis of Houska model and Cheng’s idea that wax crude oil contains both complete and partial reversibility structures, is the most suitable model to describe the thixotropy of wax crude oil
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Authors: Peng Shao, Dong Quan Wang, Chun Rong Liu, Yu Xiao Zhu
Abstract: Explosive lining is a new method to construct underground space in soil. By making the most of compressibility of soil and thixotropy of concrete under explosive loading, this method offers an efficient path to form a cavity and its concrete support layer synchronously. In order to investigate the forming effect, a series of contrastive laboratory tests, including explosive lining method and conventional explosive compaction method, were performed under same soil and explosive conditions. Results show that measured dynamic stress and displacement by explosive lining method are higher than that of by conventional explosive compaction method under same equivalent radius, and the range of compact region in soil is larger too. Similarly, the physical and mechanical performance indexes of soil, such as water content and cohesion are superior to that of by conventional explosive compaction. It is approved that an even thickness concrete support layer can be formed in one-shot forming process by explosive lining, and there is no evident cranny region in the soil around the cavity.
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Authors: S.H. Jazayeri, A. Salem, Giorgio Timellini, E. Rastelli
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Authors: Wei Wei Shan, Ju Fu Jiang, Shou Jing Luo
Abstract: Thixotropy is the most important characteristic of semi-solid materials, and it is decided by the variation of microstructure during action of handling. In this paper, for the sake of the industrial thixoforming and numerical simulation, microstructure and stress variation of semisolid magnesium alloys during isothermal compression is researched. Here, samples are heated to the desired temperature in the empty space with various holding times and compressed horizontally. Stress–strain curves during compression can be given directly by the experimental computer, and each of curves show a peak stress in a small strain and then decrease rapidly, which originally because of the thixotropy of semisolid materials. Moreover, thixotropy of semisolid magnesium alloys is clearer with the evolution of microstructures including agglomeration and deagglomeration of solid particles and the moving way of liquid at different places and strain under different conditions. Microstructures during isothermal compression show that the deagglomeration of solid particles increase with increasing the strain rate, therefore, the thixotropy of semisolid magnesium alloys increases. However, when solid volume fractions are lower, the agglomeration of solid particles doesn’t change obviously with increase or decrease factors, meaning that the thixotropy is smaller. Relationships between thixotropy and microstructure at other different conditions are also given according to the experiments and analysis.
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