| Budget Amount *help |
¥13,300,000 (Direct Cost: ¥13,300,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2004: ¥11,500,000 (Direct Cost: ¥11,500,000)
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| Research Abstract |
Results of present research is summarized as follows.
1._Mechanism of dewatering in vacuum processing method on the consolidation theory
The 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
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o discussed.
2. Clarification of behavior of air bubble in vacuum processing concrete
The 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 concrete
Main 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 bleeding
Purpose 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
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