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Quantitative evaluation of segregation behaviors of fresh concrete and influential factors on them

新拌混凝土离析行为的定量评价及其影响因素

基本信息

批准号：
16360214
负责人：
YAMAMOTO Yasuhiko
金额：
$ 6.78万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360214/
关键词：
fresh concrete granular materials mechanical law segregation bleeding segregation resistibility model segregation test pore water pressure 材料分離数値解析せん断実験分離構成則多相モデル LAT実験

项目摘要

This research aims to clarify quantitatively the segregation behaviors of fresh concrete by a microscopic approach, and to develop a segregation resistibility test method. The results of present work can be summarized as follows.(1)One-side shear test apparatus incorporating laser irradiation device was made and used to examine, by means of Laser-Aided-Tomography, the movement of irregular particles under shear force. The observed information such as changes in contact angles and moving distance of the particles were used for later theoretical parts of this work.(2)Characteristics and behavior of granular materials in fresh concrete were theoretically investigated based on the multi-phase structural model, which had been proposed by Li, co-operator of present work, to clarify mechanical constitutive laws of fresh concrete under both non-vibrated and vibrated conditions, and a non-linear deformation resistibility model of fresh concrete was proposed.(3)Using the mechanical constitutive … More laws, segregation behaviors of coarse aggregate particles in fresh concrete were investigated to formulate their mean sedimentation rate for the cases where concrete was in a standstill or vibrated state or in the state of deforming and/or flowing. Also, effects of various factors on the segregation rate, including mean particle size, fluidity of fresh concrete, elapsed time, difference in density between coarse aggregate and matrix mortar, normal stress, and others were quantitatively clarified.(4)After formulating pore water pressure and its change with time for fresh concrete in both static and vibrated states, equations for expressing both amount and rate of bleeding were derived by applying Darcy Law to bleeding of fresh concrete, and factors influencing on the bleeding phenomena were quantitatively clarified.(5)A formula of deviation ratio of gravity center, which could be used to evaluate the degree of segregation of fresh concrete, was deduced, and a segregation resistibility model was suggested for fresh concrete in static state.(6)A series of shear tests were made to verify the mechanical constitutive law of fresh concrete using an apparatus which was a stratified shear box incorporated with an γ-ray density meter. This apparatus was proposed for testing the segregation resistibility of fresh concrete. Less

本研究旨在从微观角度定量地阐明新拌混凝土的离析行为，并建立抗离析试验方法。本文的研究结果可以总结如下。(1)制作了带有激光照射装置的单侧剪切试验装置，利用激光辅助层析成像技术检测不规则粒子在剪切力作用下的运动。观察到的信息，如接触角的变化和粒子的移动距离被用于这项工作的后期理论部分。(2)基于本文合作者Li提出的多相结构模型，从理论上研究了新拌混凝土中颗粒材料的特性和行为，阐明了新拌混凝土在非振动和振动条件下的力学本构规律，并提出了新拌混凝土的非线性抗变形模型。(3)利用力学本构定律，研究了粗集料颗粒在新拌混凝土中的离析行为，得出了混凝土处于静止状态、振动状态、变形和/或流动状态下的平均沉降速率。此外，还定量地阐明了各种因素对离析率的影响，包括平均粒径、新混凝土的流动性、经过的时间、粗骨料和基质砂浆之间的密度差、正应力等。(4)在给出静、振动状态下新拌混凝土孔隙水压力及其随时间的变化后，将达西定律应用于新拌混凝土的泌水，导出了泌水量和速率的表达式，定量地阐明了影响泌水现象的因素。(5)推导了可用于评价新拌混凝土偏析程度的重心偏差比公式，并提出了新拌混凝土静态抗偏析模型。(6)采用层状剪切箱配γ射线密度计进行了一系列剪切试验，验证了新拌混凝土的力学本构规律。提出了一种试验新拌混凝土抗离析性能的装置。少