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Determination of empty cylinder apparatus fresh rheological properties of self-compacting concrete

Author: ShaoQiaoXi
Tutor: ShiJianJun
School: Nanhua University
Course: Structural Engineering
Keywords: Fresh self-compacting concrete Plastic viscosity coefficient Shear
CLC: TU528
Type: Master's thesis
Year: 2010
Downloads: 89
Quote: 1
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Abstract

Self-compacting concrete (Self Compacting Concrete, referred SCC), also known as self-leveling concrete at low water-cement ratio has high fluidity without segregation, no bleeding, can not vibrated by gravity through leveling and full template and parcel of the new reinforced concrete. This new material has so far in Japan, Germany, Britain, the United States and Canada and other countries have begun to use self-compacting concrete, is expected in countries water conservancy, transportation, mining, construction and other engineering structures has broad application prospects. One of the key scientific and technological issues are: (1) self-compacting concrete rheological constitutive model; (2) SCC mix rheology new perspective to study the various components of self-compacting concrete interaction and workability of the mechanism and test methods numerical simulation. For a long time, people have been exploring simple, accurate determination of the rheological properties of test methods, but so far there is no universally acceptable standards or specifications, or have formed the scientific method. Therefore, the research and development of both a practical and easy to use, but also more scientific and reflect the rheological properties of concrete test equipment and test method has very important practical significance. In this paper, the existing research data, based on the test methods to innovate, which uses vertical continuous loading method; Meanwhile, the rheometer was also innovative design, using pulley principle, empty cylinder apparatus sidewall Act (referred to air cylinder apparatus France ). Combined with mechanical analysis, determination of fresh rheological properties of self-compacting concrete (shear stress and shear rate relationship). The specific work is as follows: (a) trials study new rheometer (hammer test, tester test cylinder, air cylinder instrument test) Determination of fresh rheological properties of self-compacting concrete feasibility. (2) study to determine the size of the new rheometer, load load load load volume and the amount of grading, etc., and to form a relatively standard method. (3) the introduction of new rheometer test different intensities of fresh self-compacting concrete for testing to determine the different intensity of fresh self-compacting concrete rheological constitutive model. (4) According to the test using the discrete element principle (ie PFC particles streaming software) on the workability of fresh concrete test trials (slump test) carried out simulation calculation and analysis. By study reached the following conclusions: (1) a feasibility study to improve test equipment to get: Improved Hammer test due to dynamic acceleration sensor can not measure weight in fresh self-compacting concrete changes in acceleration during movement failed; cylinder instrument test is based on the premise of a certain assumption cylinder walls down to determine the frictional resistance (shear stress) and the bottom surface resistance (normal stress) the size, it is difficult to determine whether consistent with the actual situation is assumed; however, based on the above two tests failed Experience based on the improvement after a reasonable trial calculations and data analysis to improve the air cylinder instrument test technology is relatively feasible. (2) in a number of assumption, based on the use of force and reaction and mechanical balance principle the test data processing, combined with mathematical tools MATLAB7.1 in Curve Fitting Toolbox CFTOOL on rheological properties of fresh SCC intends numerical value mixed together to obtain a new self-compacting concrete rheological constitutive model; literature obtained with fresh self-compacting concrete rheological constitutive model results were compared to determine the fresh determination of rheological properties of self-compacting concrete new test method, New test equipment. New test method is a continuous vertical loading method (namely the use of pulleys works, for five consecutive mass loading); new test equipment, is an empty cylinder apparatus sidewall friction law (referred to air cylinder apparatus France). (3) by the C30, C40, C60SCC test analyzes of: fresh self-compacting concrete instantaneous shear stress and shear strain rate is linear, ie the instantaneous fresh concrete shear stress increases with shear strain rate increases with shear Cutting speed reduction should be reduced. Fresh self-compacting concrete as the intensity increases, the yield stress decreased slightly, while the plastic viscosity coefficient has increased. Fresh self-compacting concrete between 70-120 Pa yield stress and plastic viscosity coefficient within 100-180 Pa · s, while the fitting error and test errors are less than 10%. (4) the theory of particle flow numerical simulation of the specimen is a process of continuously changing, and debug various micromechanical parameters (including particle size) of the process. Based on the principle of discrete element fresh SCC slump test simulation studies show that: select the maximum particle size is the minimum size of five times, choose the smallest particle diameter of 0.2cm, the simulation results more reasonable.

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