Control of Free Water Behavior and Improvement of Durability of Concrete by Dewatering

本文的研究成果概括如下：1.基于固结理论的真空处理法降水机理研究混凝土渗漏量对混凝土板面强度和硬度有显著影响。据报道，真空脱水是制作高密度、高强度混凝土的有效方法。在本研究中，作者指出，真空处理混凝土的强度分布和密度分布之间存在着很强的相关性，两者都是从混凝土顶面逐渐减小到15 cm左右的深度。本研究的主要目的是基于固结理论，探讨这种强度和密度分布的发生机理。本文报道了砂浆和混凝土中成分分布的调查结果。此外，还提出了一种预测真空处理混凝土强度的方法--ALS…不再讨论更多内容。真空处理混凝土中气泡行为的澄清混凝土中的气泡在真空处理过程中会膨胀，有可能影响硬化混凝土的质量。从所提出的可见模型的实验结果可以清楚地看出，当真空处理持续超过约10分钟时，混凝土中的气泡有可能增加。新拌混凝土中游离水行为的澄清本研究的主要目的是通过提出一种直观的评价方法来检验砂浆中游离水的上升行为(渗漏)。进行了Ex.1至Ex.3的一系列实验。在实验1中，观察到随着自由水注入砂浆，有色液体的上升路径。在实验2中，考察了水灰比和注入有色液体的体积对其上升距离的影响，并将内渗水的行为理想化以便于建模。在实验3中，通过使用模型材料的二维可视化实验验证了所提出的模型的适用性。结果表明，所设计的可视化评价方法可以定性地检测砂浆中的渗漏行为。此外，有色自由水的上升过程清楚地表明，所提出的方法适用于讨论实际砂浆和混凝土的渗漏行为。基于素混凝土单轴压缩强度随强度变化的三维有限元分析，探讨了Drucker-Prager模型中采用的内摩擦角对混凝土受压破坏状态的影响。通过引入内摩擦角(30°和53°)不同取值的分析，指出：1)试件沿试件纵向的破坏区域随试件尺寸的增大呈成比例减小的趋势；2)内摩擦角为53°的试件内部的等效应变分布可以代表一般的破坏形态。较少

Results of present research is summarized as follows.1._Mechanism of dewatering in vacuum processing method on the consolidation theoryThe strength and hardness of concrete slab surface is considered significantly affected by bleeding of concrete. It has been reported that dewatering by vacuum processing is quite effective to make concrete high density and high strength. In this study, the authors have pointed out that there is a strong relationship between the strength distribution and density distribution in the vacuum processed concrete, both gradually decreasing from the top surface to about 15 cm depth of concrete. Main purpose of the present study is to discuss the mechanism of the occurrence of such distribution of strength and density, based on consolidation theory. The present paper reports the results of the investigation on the distribution of ingredients in mortar and concrete. Further, a prediction method for the strength improvement of concrete by vacuum processing is als … More o discussed.2. Clarification of behavior of air bubble in vacuum processing concreteThe bubble in concrete expands when the vacuum process is carried out, and there is a possibility that the bubble influences the quality of the hardened concrete. From the result of experiments with a proposed visible model, it has become clear that there is a possibility that bubbles in concrete increase when the vacuum processing continued for a longer than about 10 minutes.3. Clarification of free water behavior in fresh concreteMain purpose of the present study is to examine the rising behavior (bleeding) of free water in mortar by using a proposed visible evaluation method. A series of experiments of ex.1 to ex.3 was carried out. In ex.1, rising path of colored liquid as free water injected into mortar was observed. In ex.2, effect of water-cement ratio and volume of the injected colored liquid on its rising distance was examined, and the behavior of the internal bleeding water idealized for modeling. In ex.3, applicability of the proposed model was verified through a 2-dimensional visualization experiment, using model materials. Consequently, it was shown by the devised visible evaluation method that the bleeding behavior in mortar can be checked qualitatively. Moreover, the rising process of the colored free water showed clearly that the proposed method is applicable to discuss the bleeding behavior in actual mortar and concrete.4. Uniaxial compression FEM analysis of cylindrical concrete with strength variation due to bleedingPurpose of the present study is to discuss the compressive failure state and the effectiveness of internal friction angle used in the Drucker-Prager model, based on the uniaxial compression 3-D FEM analysis of plain concrete with the strength variation due to bleeding. As a result of analyses which introduced the different values of internal friction angle (30 and 53 degree), it has been pointed out that 1) the failure zone along the longitudinal direction of specimen shows tendency of proportional reduction with the increase in the size of a specimen, and 2) the distribution of equivalent strain inside a specimen obtained from the analysis with internal fiction angle of 53 degree can represent the ordinary failure pattern. Less