In order to evaluate the corrosion of reinforcing steel in canoe with non-destructive methods is one of indispensable items for maintenance of concrete structures. It is expected that some evaluation methods are established in this subject. Through a model experiment using different sized steel plates, the change in electrochemical response of steel was grasped with non-destructive methods such as half-cell potential, polarization resistance (AC impedance), and electric current. The numerical analysis of macro-cell corrosion and calculation of micro-cell corrosion were performed by applying experiment results This study showed that it was possible to divide the corrosion into the macro-cell and micro-cell corrosion and was possible to estimate the steel corrosion from these results.

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Curing is very important for its good performance for early age. However, many reports suggest that removal of formwork is too quick for early age. Upon been exposed to the drying conditions, the cement hydration is not able to progress. In this research, the aim is to find out the effect of drying. When cement hydration was temporarily stopped, there were many large pores remaining after drying. On the other hand, when moisture was re-supplied into the specimens after drying, cement hydration was restarted and the remaining large pores became smaller. However, the compressive strength could not be recovered. The reason is that re-supplying of moisture will produce different hydration products and microstructures and also there are some cracks in the specimens.

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When RC columns receive cyclic loading with large transformation, the bearing capacity of RC columns tends to decline suddenly after flaking cover concrete. The purpose of this study is to prevent sudden decline of the bearing capacity even in large transformation, by locating hoop reinforcement inside axial reinforcement nearby the base of the RC column. We report about the ductility and extent of damage, from the result of reversal cyclic loading test to the column that is reinforced in this way.

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Water content is a critical parameter strongly affecting the durability of concrete structures. Therefore, a simple and accurate measurement is desired for quality inspection of as-delivered concrete. This paper describes a calculating method of water content of fresh concrete with the density and air content measurements. The fluctuation of material densities and the measurement error of air content were found to strongly affect the calculation results. However, the water content could be calculated with an accuracy of ±2kg/m³ by precisely measuring the air content and acculately determining the density of concrete. With a measuring time of 5 minutes, the proposed method was proven highly applicable to field measurement of water content of concrete.

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This paper is intended to investigate bearing capacity of the anchorage method for transmission tower legs into a new type foundation, which is made of a footing and a single pile, subjected to pull-out load. We found two main failure modes in this anchorage method. One is due to splitting crack stress with yield of footing's main bar. And the other is due to punching shear. We proposed bearing capacity formulas for both failure modes.

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This paper presents the experimental results on T-shaped reinforced concrete beam-to-column joint with corroded rebars. Rebars at the joint were subjected to accelerated corrosion by means of the electrolytic technique. The degree of corrosion was monitored by electrochemical methods. Then flexural and shear loads were repeatedly applied to the joint. Decrease in load-carrying capacity due to corrosion was evaluated by taking into account the cross-sectional loss of rebar and degradation of bond performance between rebars and concrete at the joint. It was clarified that local horizontal displacement of the column was affected by deterioration of bond performance.

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Ultimate failure of concrete members retrofitted by surface overlaying with polymer cement mortar may accompany sheer peeling at the bond interface under combinations of structural systems and loading conditions. By this research, the bond behavior was solved experimentally and was grasped. Experimental method was that shearing bond stress was applied to the bonding interface of the specimens retrofitted by surface overlaying method with polymer cement mortar. The stress transfer mechanism of this method was understood from strain distribution of reinforcing bar and mortar. It was shown that the peeling failure energy of retrofitted part of this method can be calculated using bond stress and displacement of bond interface.

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The antifreezing admixture fulfils large role for decreasing the traffic damage by the freezing and snowy road. On the other hand, sprinkling amount has been increasing year by year. The technology which measures the antifreezing admixture has not been established. In this study we try to construct the system of the measuring the amount of the antifreezing admixture by measuring chlorine in the antifreezing admixture using fluorescence X-ray.
The proportional counter is effective for this measurement. The measuring value is mainly depended on X-ray irradiation and specimen distance from the detector and X-ray tube.

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In the thermographical detection for the internal flaw of RC floor slabs, several way as new detection method have been discussed, such as the passive method using the fluctuation in solar radiation and the active one using the difference of temperature by the artificial heating system. However, resulting from our continuous experiment, two primary issues should be solved were obtained; first, few difference of temperature on the RC floor slab bottom on the passive method and uneven state of heating and second, set up of the scaffoldings on the active method. In this study, a new diagnosis method focused upon the pavement heat of the asphalt was proposed. As a result, the part of low-temperature at the bottom faces of specimens, which clearly indicates the flaw, was visualized and detected.

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This paper aims to develop the evaluation method of chloride penetration in cracked concrete. The method is based on a simple apparent diffusion theory of chloride through concrete, enabling the prediction by obtaining the data at periodic inspection. Considering the chloride distribution in crack and mass preservation rule of chloride ion and applying different boundary chloride conditions to cracked portion and other surface, chloride penetration in cracked concrete can be predicted numerically in case of the wetting condition and cyclic wetting and drying condition. And effects of crack widths and apparent diffusion coefficient inside crack can be evaluated numerically.

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The ultrasonic testing that is one of non-destructive method is applied to evaluate the quality of concrete structure or to determine its crack depth. However, it is clarified neither how the ultrasonic waves propagate in concrete, nor what kind of influences of boundary conditions and initial state on ultrasonic waves. In this study, therefore, not only experimental tests but also analytical examinations are carried so as to clarify the propagation of the ultrasonic wave in concrete with a crack and to aim the extension of the application range and the reliability improvement of the ultrasonic wave method as the quality-evaluation technique of concrete. From this study, the propagation of ultrasonic wave in the concrete was visualized, and the propagation of ultrasonic wave in concrete was clarified by the distributions of displacement.

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This study focuses on characteristics of concrete in tensile deformation and cracking criteria, both of which are necessary material characteristics to predict drying shrinkage crack in concrete members. The influences of loading rate and drying duration on tensile characteristics and cracking stress of concrete were investigated through conducted systematic uniaxial tensile test. Empirical equations for effective elastic modulus and cracking stress were formulated based on the test results. It was verified if these equations are applicable to induced stress and associated crack in concrete members due to actual drying shrinkage of concrete by the uniaxial restraint shrinkage test.

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Characteristics in tensile deformation and cracking criteria of concrete, both of which are necessary material properties in predicting drying shrinkage crack in concrete members, were investigated with the uniaxial restraint shrinkage tests under various condition. Influences of induced stress history due to restraint autogenous shrinkage and ratio between length of drying edge and cross sectional area of the member on characteristics in tensile deformation and cracking criteria of concrete were clarified. It was verified that the proposed prediction method for shrinkage crack could successfully simulate the various experimental results done by other researchers.

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Two kinds of finite element model, such as a smeared crack model and a discrete crack model have been proposed up to now. These elements can represent a crack that occurs in a concrete because of the strain localization. In this study, a smeared crack model with embedded localization zones was newly proposed. This element can reduce the mesh-size-dependence less than the smeared crack element proposed previously. Analytical results of RC beams failed by diagonal tension failure were compared with the experimental results. Finally, the F. E. M, analysis using the proposed element can decrease the mesh-size-dependence, and estimate an occurrence and/or a propagation of inclined cracks and a size effect of shear strength of RC beams reasonably.

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It is indispensable to know the establishment of material property evaluation method and the material influence proportion in order to understand the flow deformation resistance of the asphalt mixture. In this study, focusing on the viscoelasticity of the polymer modified bitumen and geometrical properties of coarse aggregates, their measuring and evaluation methods were examined. The examination of relation between the obtained material property values and porous mixture properties revealed that mortar consisting of asphalt and aggregate granules is highly correlated with the dynamic stability of mixture and that the flow deformation of mixture is more influenced by the microtexture of coarse aggregate surface rather than large geometrical properties such as coarse aggregate flatness.

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This paper deals with how to use a large amount of powdered industrial by-products, such as ashes from the iron casting process and reducing slag from the electric furnace, for concrete. The key in this study lies in how to reduce water content in concrete for getting proper mixing capability. The second point is how to control flash setting and expansion of concrete caused by reducing slag. The addition of proper amount of sodium chloride and gypsum in concrete can solve the problems and the application of the concrete to armour unit was done successfully in the field of sea. In addition, it is confirmed that the reducing slag can prevent hexavalent chromium dissolving out from concrete.

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Mechanical properties of young-aged concrete influence the prediction of thermal cracks of mass concrete structures. This paper presents an experimental study on the bond characteristics between the young-aged concrete and deformed bars by the axially loaded tension test in order to reproduce the tensile stress field. The experimental factors of the present study are mainly bar diameter and cover thickness, these tests were carried out through various concrete ages. As the test results, the tendency that bond characteristics change along with concrete age was confirmed, and its bond mechanism was influenced by shear failure due to reinforcement.

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The nonlinear earthquake response analysis for RC bridge piers was conducted for the purpose of verifying the validity of the static and dynamic lattice model considering the buckling evaluation of reinforcing bar. The buckling behavior of reinforcing bar is represented by a spatially averaged stress-strain relationship for reinforcing bar in compression. It has been confirmed that the static lattice model analysis considering the buckling can accurately predict the behavior of RC bridge piers. By the dynamic lattice model analysis considering the buckling, it has been found that the post-peak behavior can be captured with an appropriate accuracy as well as the static analysis in which two different types of earthquake motion were used for the verification of seismic performance of RC bridge piers.

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Asphalt concretes with high resistance to deformation, which contain large-sized aggregates, are effective in airport pavements. In this paper, its applicability in airport asphalt pavement surface courses was investigated by conducting the laboratory tests and field tests. As a result, the asphalt concrete with large-sized aggregates has higher resistance to rutting, and has the capabilities in other requirements equivalent or superior to the usual, in comparison of usual asphalt concretes. It developed that the asphalt concrete with large-sized aggregates could be applied to airport pavement surface courses.

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