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

目前的研究结果总结如下：1。基于固结理论的真空处理法脱水机理混凝土板表面的强度和硬度受到混凝土出血的显著影响。已有报道称，真空脱水是实现混凝土高密度高强的有效方法。在本研究中，作者指出真空处理混凝土中的强度分布与密度分布之间存在很强的关系，从混凝土顶表面到约15cm深度，两者都逐渐减小。本研究的主要目的是在固结理论的基础上，探讨这种强度和密度分布的发生机制。本文报道了砂浆和混凝土中成分分布的研究结果。此外，本文还对真空处理提高混凝土强度的预测方法进行了探讨。真空处理混凝土中气泡行为的澄清在进行真空处理时，混凝土中的气泡会膨胀，并且存在气泡影响硬化混凝土质量的可能性。从提出的可见模型的实验结果来看，很明显，当真空处理持续时间超过约10分钟时，混凝土中的气泡可能会增加。澄清新鲜混凝土中的自由水行为本研究的主要目的是通过提出的可见评价方法来检查砂浆中自由水的上升行为（出血）。进行了例1至例3的一系列实验。例1中观察了有色液体作为自由水注入砂浆的上升路径。在例2中，考察了水灰比和注入色液体积对其上升距离的影响，并对内出血水的行为进行了理想化的建模。在例3中，通过使用模型材料的二维可视化实验验证了所提出模型的适用性。结果表明，所设计的可视化评价方法可以定性地检测砂浆的出血行为。此外，有色游离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中的出血行为。柱状混凝土单轴压缩随渗漏渗漏强度变化的有限元分析本研究的目的是在素混凝土单轴压缩随渗漏渗漏强度变化的三维有限元分析的基础上，探讨Drucker-Prager模型中所采用的压缩破坏状态和内摩擦角的有效性。通过引入不同内摩擦角值（30度和53度）的分析，指出1)试件纵向破坏区域随试件尺寸的增大呈比例减小的趋势；2)53度内摩擦角分析得到的试件内部等效应变分布可以代表一般的破坏模式。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