In this paper, the two models are proposed so as to estimate corrosion rate of reinforcing bar embedded in concrete due to neutralization. In order to clarify mechanisms of reinforcing bar corrosion, the experiment that corrosion of reinforcing bar due to concrete neutralization under alternate drying and wetting conditions was carded. Measured corrosion potential, corrosion area ratio and specific resistance of concrete were used in these models. Through this analysis, it is confirmed that corrosion of reinforcing bar is oxygen control in high temperature and high humidity, specific resistance control of concrete in low temperature and low humidity. The amounts of corrosion on the theoretical analysis not only show the same tendency, but also show almost the value compare with experimental results. It is confirmed that these corrosion models of reinforcing bar is useful for calculation of corrosion amounts.

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Reinforced concrete structures such as a containment vessel, a support structure of the reactor, piping systems and facilities for storing high level radioactive waste in a nuclear power plant are exposed to a high temperature condition. Changes of physical properties of concrete and reinforcement caused by high temperature influence on mechanical behavior of these structures and internal stresses are induced by difference of thermal coefficients between concrete and reinforcement that was reported in the previous paper by the author. These are the special features in high temperature conditions. Temperature dependence of physical properties of concrete and reinforcement are summarized in the paper based on the experimental results

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In this study, the fundamental properties and mechanical behaviors of cylindrical mortar members reinforced by fiber sheet were examined. This member has compressive strength of 159MPa and tensile cracking strength of 27MPa. This high-strength member was used not only as compression diagonal member but also as tension diagonal member of PC truss beam, and then the loading test of PC truss beam was carried out. These high-strength members worked well as tension diagonals until the maximum load, and PC truss beam showed the ductile behavior even after the break of some tension diagonal members.

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This study aims to improve workability of extremely stiff consistency concrete by using some kinds of admixtures and by arranging vibrating conditions (frequency, vibration period and acceleration).
As the results of this study, it was found that flowability of the concrete under vibrating is improved by using fly ash that has spherical particles and by making the range of particle size distribution wider than that of cement. And it was made clear the relationship between workability of the concrete and the vibrating conditions.

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This paper describes the evaluation of degradation by the calcium ion leaching from concrete. Numerical model to predict the degradation of calcium leaching is constructed by the chemical equilibrium of calcium, movement analysis of diffusion and advection, and the change of mechanical properties and porosity.
From the comparison of the results of numerical simulation and the results of investigation for thirty-year through one-hundred-year old actual structures, it was concluded that the developed model could satisfactorily express the fundamental degradation mechanisms. And it was found that the water to cement ratio and calcium ion concentration at the boundary had large effect on the degradation speed.

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Shear capacity of RC beam/column member with self compacting high strength concrete and high strength steel was investigated. The following results were obtained; the increase of concrete compressive strength scarcely affects shear capacity carried by concrete in higher ranges than 50MPa, size effect became remarkable, and that concrete strength should be also carefully considered to use high strength steel as stirrup effectively. The experimental results and the current design equation were compared, and FE analyses based on a shear transfer constitutive model considering the fracture phase of high strength concrete were carried out. It was verified that the proposed analytical method could evaluate shear capacity and deformation of RC beams with high strength materials.

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The purpose of this study is to establish and propose a numerical analysis method for predicting the long-term Ca leaching from concrete. In this method, the Ca leaching ratio can be estimated using the model about ion migration and Ca leaching in concrete. Nernst-Plank equation, Debye-Huckel theory and electro-neutrality condition are used for modeling ion migration in concrete. Also, Buil's model is used for modeling Ca leaching from cement paste to pore solution. In order to verify this method, the prediction results are compared to the survey results of an existing structure used for 100 years. As a result, the numerical analysis method for predicting Ca leaching from concrete is established. Moreover, the Ca leaching from concrete for 1000 years is predicted using this method.

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In our past paper, the bond behaviour between one layer fiber sheets and concrete was investigated, and the bond strength between one layer fiber sheets and concrete was estimated. In this paper, the bond behaviour between multi-layer fiber sheets and concrete was investigated by non-linear finite element method and was checked by these experiments. The stress-strain relation of the concrete with one-layer fiber sheets proposed by our past paper was applied to this analysis, and the bond behaviour between multi-layer fiber sheet and concrete has been estimated mostly. By multi-layer fiber sheets, the effective bond length is increased. Although the bond strength of fiber sheets and concrete increases by multi-layer fiber sheets, it is not proportional to the number of fiber sheets. Furthermore, the bond strength between multi-layer fiber sheets and concrete was calculated, and experiment value has been estimated mostly.

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Pavement is modeled as an elastic structure composed of a semi-infinite body and layers of finite thickness extended infinitely in a horizontal direction. Load acting in a horizontal direction at the surface is uniformly distributed over a circular area. Navier's equation is solved analytically by employing Hankel transformation theory. Furthermore, using the principle of superposition, a program is developed, which can find the response of multiple shear loadings. Accuracy of the results is confirmed by comparing the results from BISAR using some example problems. The comparison shows that the stress outputs from BISAR yield erroneous results at the pavement surface.

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Experiments were carried out to clarify quantitatively the effects of spraying variables on the quality of high-strength sprayed mortar-plates. Premixed mortar mixtures with adequate proportions were used for spraying, which was made on vertical surface of molds. The quality of sprayed mortar was evaluated by comparing the flexural strength, compressive strength and density of specimens that were sawed out from the mortar. In the cases of sprayed mortar with welded wire mesh embedded in, the probability of appearance of visible pores behind the mesh was also examined.
It was shown that calculated mean pressure, which represented an approximate magnitude of vertical mean pressure acting on spraying surface, could be used as an index for evaluating the total effects of spraying variables on the quality of sprayed mortar.

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This study is aimed to create a model for predicting the chloride ions migration process of concrete due to the compound interaction of salt damage and carbonation through an investigation into the immobilization of chloride ions in cement hydrates and the release of them when degradation of cement hydrates occurs due to carbonation. The available capacity of cement hydrates to immobilize chloride ions and the release of chloride ions accompanying with the carbonation of cement hydrates were determined by artificially synthesized cement hydrates which were immersed in artificial pore solution of concrete. Based on the above experiments, a model for characterizing the process of immobilization and release of chloride ions was established and its validity was verified by comparing calculated data with the data from the tests with cement paste and cement mortar specimens.

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In order to fill up experimental data on shear failure of RC members subjected to axial compression, a series of experiments were performed using beam specimens in, which parameters such as axial compression and shear span-depth ratio were varied. From the results, an increment of the capacity on the diagonal tension cracking was more remarkable as the shear span-depth ratio was smaller, and using decompression moment method which is adopted in the standard design code, the effect of axial compression on the diagonal tension failure with shear span-depth ratio could be expressed linearly. On the contrary, encouraging effect of axial compression on the shear compression capacity was decreased linearly as the shear span-depth ratio was smaller.

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This paper has been conducted to develop calibration method for funnel type flowing test apparatus for self-compacting concrete. A standard sand produced at Toyoura has been selected after carrying out selection tests of standard material for calibration. Variations due to production and types of the V type and O type testing apparatus, and selection lots of standard sand were obtained. Variation due to production of the apparatus are larger than selection lots of the standard sand. Three types of self-compacting concrete were produced to measuring flowing time by the use of O type, V type and S type testing apparatus. A calibration method was proposed for funnel type flowing test apparatus.

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This paper presents the applicability of fracture control design concepts to the repair strategy for crack injection repair in concrete structures. The mechanical behavior including crack patterns depended on the properties of injection materials. The stiffness of the repaired specimen with un-injected parts became lower than that of original one. Most repair strategies for crack injection repairs involve the injection materials each having good bonding, high strength etc. These good materials, however, gave new cracks in the bulk concrete because of higher strength of injections and its interfaces. It was also discussed that the material selection based on the fracture control design concepts might be important for the maintenance of concrete structures.

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The strengthening effect using steel plate on the structural performance of reinforced concrete beam with vertical construction joint was studied. Vertical joint was located within the shear span of the beam and steel plate was used to cover the joint so that the beam could perform structurally as normal beam without construction joint. The tensile strain of the stirrup increased noticeably at the position near the vertical joint. However, the steel plate could reduce local increase in the strain of the stirrup. In addition, it was found that the steel plate contributed to resist the part of the shear force on the beam with the stirrup resulting in the prevention from the stirrup failure.

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In order to regulate the quality of concrete, the production should be begun with accurate measurement of the specified quantities of materials. However, the accurate and quick measurement of the surface moisture of fine aggregate is difficult for most production systems currently in operation in ready-mixed concrete plants. To solve this problem, the authors devised “the immersed fine aggregate batching method, ” in which fine aggregate is immersed in water and batched in a saturated condition, to calculate accurate quantities of water and fine aggregate independent of fluctuating surface water. This paper reports on the verification tests for putting this concrete production system, in which immersed fine aggregate is batched, into practical use. Batching control of immersed fine aggregate and specifications of the equipment are also described, while reporting the quality confirmation test results made using this method.

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Marine durability of 15-year old uncracked and precracked concrete specimens made with ordinary portland (OPC), slag (Type A (SCA), B (SCB) and C (SCC)) and fly ash (Type B (FACB)) cements was investigated. Compressive strength, chloride ingress, corrosion of steel bars in concrete, and crack healing were evaluated. Chloride ingress and corrosion of steel bars in concrete are sequenced as OPC>FACB>SCA>SCB>SCC. Crack healing is observed for small crack widths (≤0.5mm) irrespective of the cement types. Large crack widths, such as 1.5, 2 and 5mm are not healed and significant loss of diameter is observed. Voids at the steel-concrete interface cause the formation of corrosion pits.

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RC deep beams with the effective depth of 200, 400 and 600mm and with the transverse reinforcement ratio varied from 0.0, 0.4 to 0.8 percent are tested. The measurement on the distribution of the local strains inside specimens for both concrete and reinforcements is performed by embedded strain gages inside the deep beams. The localized compressive failure zone of concrete in RC deep beams, which failed in shear compressive mode, is identified. Thus, the localized failure volume, V_p, and the fracture energy, G_Fc, are quantitatively evaluated. It is proved that concepts of G_Fc from the uniaxial compression tests are also applicable to concrete in RC deep beams which locally fail in compression.

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