Segregation Characterisics of Fresh concrete

对混合料配比变化较大的混凝土进行了拖球粘度计试验、坍落度试验、漏斗试验和T形管试验，并用离散单元法进行了模拟。主要研究结果如下：(1)通过拖球式粘度计试验确定了Bingham常数与配合比之间的关系，并通过DEM分析确定了Bingham常数与DEM参数之间的关系。通过对坍落度试验、漏斗试验和T形管试验的DEM分析结果表明，只要分析中的Bingham Constans与试验结果接近，就可以较好地模拟新拌混凝土的行为。(3)然而，由于分析的偏差，Bingham常数与DEM参数之间的关系式的适用范围较窄，超出这个范围不能模拟新混凝土的行为。通过DEM分析，定性地揭示了漏斗试验和T形管试验中粗集料的离析以及由此产生的堵塞发生和扩展的位置和方式。

Dragging Ball Viscometer test, slump test, funnel test and T-shaped tube test were carried out on con- cretes of which mix propotions were changed widely, and these tests were simulated by DEM (distinct element method). The results can be summarized as follows.(1) Relations between Bingham constants and mix proportions were determined based on dragging ball viscometer tests, and relations between Bingham constants and DEM parameters were determined by DEM analysis. Equations to determine DEM parameters based on mix proportions were proposed using these results.(2) It was concluded from the results of DEM analysis on slump test, funnel test and T-shaped tube test using the DEM parameters determined as above that behavior of fresh concrete can be simulated almost satisfactorily, provided Bingham constans in the analysis are near to those in the experiments.(3) However, it was also found that applicable range of equations relating Bingham constants to DEM parameters is relatively narrow due to the deviations of analysis and that behaviors of fresh concrete can not be simulated beyond this range. Further studies are needed to set up more precise equations.(4) It was made clear qualitatively by DEM analysis where and how segregation of coarse aggregate and resulting blockade occur and propagete in funnel test and T-shaped tube test.