The purpose of this study is to estimate the aerosol chloride condition and the relation between the environmental condition and chloride penetration into concrete.
  Form the exposure test, the amount of chloride ions penetrated into specimen under the same environmental condition can be estimated by the effective diffusion coefficient. And the relative influence of the effective diffusion coefficient on chloride penetration is almost same even if exposure places differ. Based on these results, the prediction method for the amount of chloride penetration and chloride distribution under aerosol chloride condition using diffusion coefficient and chloride binding capacity of binder was discussed.

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  In order to investigate the deterioration of concrete under marine environments, both concrete cores sampled from existing structures and test specimens exposed in the outdoor pool of natural seawater were examined by Vickers hardness test, EPMA and Cl penetration and carbonation depth measurements. Correlation analysis for the distributions of various elements was carried out and following interesting behaviors were observed: 1) The depth of maximum Mg²⁺ concentration was correlated with the carbonation depth. 2) Deteriorated areas in concrete specimens based on Vickers hardness were correlated with the penetration depth of Mg²⁺. This result means that the penetration depth of Mg²⁺ can be a simple indicator of concrete deterioration under marine environments.

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  A simulation model to estimate the pore structure of cement hydrates is presented. In this paper, procedures for predicting phase compositions based on the classical hydration model of Portland cement, calculating the particle size distribution of constituent phases and evaluating the pore size distribution by stereological and statistical considerations are described. To evaluate of effectiveness of this model, simulation results were compared with experimental results of the pore size distribution measured by mercury porosimetry. As a result, it was found that the experimental and simulated results were in close agreement and simulated results indicated characterization of pore structure of cement hydrates.

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  In this study, influences of the mix proportion in mortar expressed by the mass ratio of unit weights of water, fine aggregate and cement (W : S : C), the quality and the quantity of coarse aggregate on the compressive strength of high strength concrete under same water to cement ratio were examined. As a result, the phenomenon that the compressive strength varied depending on these parameters was confirmed. The image analysis using the digital image correlation method was carried out to explain the variation of the compressive strength of concrete. The difference of compressive fracture behaviors of high strength concrete was discussed by focusing on the lateral strain magnification zone obtained by this method. Different distributions of lateral strain concentration zones and damage extents in the lateral direction were observed for each case. The relationship between the variation of the compressive strength and the fracture behaviors was concluded from the distribution and the extent of increased lateral strain zones.

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  A model for dissolution rate of CO₂ gas in high pH solution based on chemical kinetics is presented in this paper. The numerical analysis values using the dissolution rate model generally correspond to experimental results for dissolution tests of CO₂ gas in simulated pore solution containing NaOH and Ca(OH)₂. On the other hand, comparison between the dissolution rate model and an equiribrium model based on the assumption that the dissolution of CO₂ in solution immediately come to equilibrium state was carried out. As a result, it was shown that the rate-controlling factor of CO₂ dissolution process in atmosphere containing 0.06% CO₂ gas was not the diffusion rate of CO₂ in the solution but the dissolution rate of CO₂ into the solution.

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  This research has developed a real-time image analyzing system for evaluating the strain generated on the surface of RC beams during the loading test. The influential parameters on the analyzed results were also examined. The developed system was applied to the four-point bending test of slender RC beams and the maximum principle strain generating on the surface of RC beams during the test was visualized. The visualized strain distribution was able to evaluate the strain concentration area, and predict the failure mode of RC beams before the load reached the maximum.

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  Recycled fine aggregate crushed by jaw crusher has a brittle part, which contains many defects such as cracks, pores and voids. This paper describes the effect of pulverize machine on the characteristics of recycled fine aggregate, especially focusing on the selective removal of defective parts in recycled fine aggregate, as well as improving both size distribution and shape of grain. As for pulverizing machines, jaw crusher, granulator, and ball mill is used. Main action of jaw crusher is due to crushing, granulator is grinding, and ball mill is crushing and grinding, respectively.

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  Electric resistivity has attracted attention as one of the index for evaluating chloride ions permeability of concrete. However, the relationship between the apparent diffusion coefficient of chloride ions in concrete and the electric resistivity is not still clarified. In this study, this relationship was disccused from some experimental results obtained by several types of specimens. Moreover, the relational expression of the electric resistivity and the diffusion coefficient was derived from Nernst-Planck equation etc., and a quantitative evaluating method of apparent diffusion coefficient of chloride ions from electric resistivity and this relational expression was examined.

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  The study presents an investigation of the shear behavior of segmental concrete beams with external tendons considering the effect of joint opening. Joint position and prestressing force that affect the joint opening have been examined based on the results of experimental procedure and FEM. The simplified truss model with the small number of degree of freedom has been modified for segmental concrete beams with external tendons. The formulations to predict the variable angle and the thickness of struts are suggested with considering the effect of joint opening. A satisfactory prediction for the shear carrying capacity and the failure mechanism of segmental concrete beams with external tendons has been obtained.

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