Simulation Analysis of Concrete Pumping Based on Smooth Particle Hydrodynamics and Discrete Elements Method Coupling
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With an increase of suction efficiency of fresh concrete pumping in confined spaces, the laminar flow state will be damaged by the return flow caused by distribution value direction changes and concrete gravity. This is a fact, but one which is rarely studied. In this work, the flow state, flow velocity, and suction efficiency of fresh concrete pumping are simulated using the coupled smooth particle hydrodynamics and Discrete Elements Method (SPH-DEM). The rheological parameters and Herschel-Bulkley-Papanastasiou (HBP) rheological model are adopted to simulate fresh concrete in the numerical simulation model. The study reveals that the error between the slump experimental result and that obtained by the HBP model is negligible. A model is therefore established for numerical simulations of the suction efficiency of fresh concrete pumping. An experimental concrete pumping platform is built, and the pressure and efficiency data during pumping are collected. A comparison of the numerical simulation with experimental results shows that the error is less than 10%.Keywords:
Particle (ecology)
The laminar flow of a thin film past a vertical wall subjected to suction is studied. An approximate solution for small porosity is obtained in the accelerated region. A relation between film thickness and distance traveled is presented.
Laminar sublayer
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Abstract Experiments were designed to compare concrete and paste flow behavior in mixtures containing water reducing admixtures by measuring concrete slump, concrete rheology, mortar rheology, and paste rheology (using low-amplitude oscillatory shear) at times up to about 2 h after mixing. Some concretes were continuously agitated, and others were allowed to rest between tests. Stiffening was observed in most of the concretes during this time. Continuous agitation reduced this stiffening. Concrete slump and paste modulus showed a weak correlation in most mixtures. Both concrete slump and paste modulus were sensitive to agitation, especially in mixtures containing a water reducing admixture. Based on these results, it is recommended that laboratory studies simulate the agitation expected in the field.
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Concrete slump test
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Abstract The effects of the amount of early strength components, retarding components and slump-retaining components of concrete admixtures on initial fluidity, slump loss and initial setting time of concrete are compared through experiments, so as to adjust the workability of fresh concrete more pertinently.
Superplasticizer
Concrete slump test
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Concrete slump test
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Focused on the static slump and dynamic slump concrete,and the influence of the static slump and dynamic slump concrete was studied.The results show that static slump of concrete has bigger than dynamic slump of concrete;the regression curve was obtained through experimental results.
Concrete slump test
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The article analyzes the causes of concrete slump loss,explores factors influencing slump from aspects of working environment and temperature,preliminary slump,construction method,pressure pumping and raw materials and so on,and puts forward preventive measures,so as to improve the concrete slump.
Concrete slump test
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مقدمه یکی از علل شایع درد کمر فتق دیسک کمر می باشد. برای تشخیص فتق دیسک کمر تست های گوناگونی از جمله Slump و SLR وجود دارد که از آن ها برای تشخیص فشار بر روی ریشه عصب استفاده می شود. برای معاینه فیزیکی فرد در تست Slump بیمار در حالت نشسته قفسه سینه ، کمر و گردن خود را خم می کند سپس یک زانو را صاف می کند و کف پا را به عقب خم می کند. در تست SLR معاینه کننده در حالی که زانوی بیمار صاف است مفصل ران او را خم می کند(در حالت سوپاین).ام آر آی یک پروسه تشخیصی استاندارد برای فتق دیسک کمر است. هدف این مطالعه مقایسه حساسیت تست های Slumpو SLR در تشخیص فتق دیسک کمر است. روش کار این مطالعه توصیفی- تحلیلی در سال 1392 انجام شد. برای 60 بیمار 18 تا 60 ساله ، که با تشخیص فتق دیسک کمر در بیمارستان های آریا، فارابی و 22 بهمن بستری شده بودند، تست های Slump و SLR انجام گرفت و نتایج این تست ها از نظر میزان همخوانی با ام آر آی بیماران بررسی شد. اطلاعات با استفاده از SPSS تجزیه و تحلیل و حساسیت هر تست محاسبه و با یکدیگر مقایسه شد. نتایج حساسیت تست های Slump و SLR به ترتیب % 3/83 و % 7/61 با تفاوت آماری معنی دار (05/0 p <) بود. طبق نتایج مطالعه حساسترین تست در بین گروه ها و زیر گروه ها تست Slump بود .در مقایسه زیر گروه ها، تست Slump برای هرنی دیسک در کلیه سطوح و همچنین در کلیه مکان ها بیشترین حساسیت را نشان داد. نتیجه گیری به طور کلی، نتایج این مطالعه نشان داد که تست Slump حساس تر بوده و به عنوان یک ابزار ارزشمند جهت تشخیص به کار می رود.
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