The influence of gypsum on the behavior of chloride ion and corrosion of steel in mortar including ground granulated blast-furnace slag (BFS) were investigated. Gypsum was added to BFS. The decrease in the amount of bound chloride ion in mortar due to the addition of gypsum is thought to be related to the reduction of the amount of Friedel's salt. The chloride corrosion of steel by intrinsic chloride ion in mortar was accelerated by the addition of gypsum. The chloride corrosion of steel by intrinsic chloride ion was found to be related to the change in pore structure and the increase in soluble chloride content due to the addition of gypsum. The addition of gypsum had no effect on the chloride corrosion of steel by extraneous chloride ion in mortar.

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Recently the phenomena have happened in Japan that spalls of tunnel lining concrete fall from its surface. Therefore the method for diagnosing interior defects of tunnel lining concrete has been desired to develop. Several diagnostic methods have been proposed, but most of them are in the test stage and don't come to practical use. In this paper, we describe the development of the diagnostic device with low frequency elastic wave and the results of the tests by this device in real tunnel to verify the method for diagnosing existence and depth of interior defects of tunnel lining concrete. We also describe the results of the tests by this device for concrete models and of dynamic numerical analysis.

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This paper describes the validity of parameters obtained from received waveform in Impact Elastic-Wave Methods for the evaluation of grouting condition in PC structure. In this study, both experimental and FEM analysis investigation was conducted. In experiment, relation between the propagation velocity, the frequency distribution and the risetime obtained from received waveforms and volume percentage of grout or difference of component material used in specimen. FEM analysis was carried out to understand the elastic wave behavior inside the specimen, which was visually identified. Finally, experiments of a real PC tank were carried out to confirm the practical applicability of this method.

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To investigate the behavior of footing under seismic loading, three 1/3 scale monolithic specimens composed of a pier, a footing, and piles were constructed, and they were loaded by the montonic loading procedure, using the shear span ratio and reinforcement ratio in the footing as the parameters. According to the test results, dominating damage was the damage at the connection up to the maximum load regardless of the difference in the shear span ratio(a/d). Shear failure was occurred by the lateral force acting to the pile and column, after the main reinforcement was yielded.

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In order to clarify the applicability of fiber model to pile-soil interaction analysis. numerical evaluations of the past loading test results are synthetically performed using 3D FEM analytical method including the local behaviors between pile and soil. It can be concluded that the local separation between pile and soil (e.g. no tensile stress exists) is effective on the response behavior of RC piles, especially in the cases that the maximum damage occurs at deep position of the pile. In addition, the accuracy of the adopted model is verified for applying to the response evaluation of pile-soil system.

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Chloride induced corrosion of reinforcing steel is a typical cause of the deterioration of RC structure. It is known that macro-cell increases the corrosion rate of steel bar. However, the amount of deterioration caused by macrocell corrosion cannot be determined from the Stern-Geary formula.
This study aims at taking into account the effect of pre-polarization of steel caused by macro-cell when calculating macro-and micro-cell corrosion rates from polarization resistance and halfcell potential, thereby clarifying how the presence of concrete cracks generated by bending moment affects the corrosion rate of reinforcing steel.

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This paper presents an application of Free Mesh Method (FMM) to the flow analysis of fresh concrete. FMM, which is a kind of meshless method, is suitable for distributed parallel processing, adaptive analysis and moving boundary problems because it is performing the calculation from the local mesh generation to the construction of the global matrix on a node-by-node basis. In this study, flow behavior of fresh concrete has been assumed viscoplastic fluid, and the constitutive law of fresh concrete is given as the Bingam-model. As the numerical examples, the L-type flow test has been simulated by this method, and the analytical results are in good agreement with the experimental ones.

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In circum-Pacific region there are a lot of low quality coarse aggregate, i.e. volcanic aggregate and coral aggregate. However there is no research that examined the strength and material permeability resistance of concrete using these low quality coarse aggregate from the circum-Pacific region yet. Therefore the purposes of this study are to investigate the strength and the material permeability resistance of low quality coarse aggregate in the circum-Pacific region and concrete using it, and to propose the effective utilization method for low quality coarse aggregate.

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Polymer cement mortar retrofitting is the strengthening method of concrete structure using reinforcing bars and polymer cement mortar, which is mainly used for strengthening of the bottom side of the slabs of bridges. In this study, the strengthened RC beams were experimented to know the failure behaviors of this method. By conducting the loading tests with various shear span ratios of the RC beam, amounts of strengthening bars and thickness of polymer cement mortar layer, the failure behaviors of the strengthened beam were reviewed. After the experiments, it was found that the failure behaviors were classified into large categories of bending, shear, center peeling-off and peeling-off in the anchorage zone. This paper mainly describes both types of peeling-off failure to review their generation mechanisms and the behavior.

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The effect of steel fiber with different size on water tightness and flexural properties of concrete was investigated. From the test results of single fiber reinforced concrete, fibers used in this research were divided in two categories of longer and shorter ones. The effect of each fiber on water tightness and flexural properties was different. From the test results of hybrid fiber reinforced concrete, the effect of combination of fibers on water tightness and flexural properties were different each other. The permeability of fiber reinforced concrete had correlation with compressive strength, and the effect of combination of fibers on water tightness was quantified using by cement-void ratio theory, which explained compressive strength of concrete.

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In order to evaluate the effect of the porosity on the dissolution, alite hydrate slabs of varying porosity were leached in water. It was confirmed that the larger porosity samples was progressed of dissolution rapidly, and the increase of the porosity was correlated with the decrease of Ca(OH)₂. With the observation of the leached samples, a clear difference between the altered part and the unaltered part was shown by EPMA. The border was termed as the ‘Ca(OH)₂ (CH)-dissolution front’. The linear relationship was found between the thickness of altered zone and the square root of time. It was confirmed that the movement of Ca ion was caused by diffusion and the rate of alteration was dependent on the porosity.

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The advantage of the MLMT (Multi-Layer Multi-Tensioning) method, which was proposed by the authors, was studied on the basis of the results of numerical analyses and loading tests. The numerical results showed that the stress concentration around the end of adhesive interface was effectively reduced by using the MLMT method. Considerably high tensioning force could be consequently applied to the reinforcing sheets. The experimental results showed that the MLMT method had advantageous effects not only on the crack initiation of the concrete structures induced at lower level of loading but also on the debonding of adhesive interface induced at higher level of loading.

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In this study, the static loading and fatigue loading tests of RC beams strengthened with Carbon Fiber Reinforced Polymar (CFRP) plate were carried out in order to investigate the flexural strengthing effects, and the effects of material property of CFRP plate and strengthening methods by using CFRP plate on the bending capacity and deformability of RC beam were evaluated. By strengthening with CFRP plate, the bending capacity of RC beam was improved largely and the sufficient fatigue performance was obtained. The use of high-strength type of plate for beams strengthened with tensioned CFRP plate and the use of middle high-elasticity type of CFRP plate for beams strengthened with adhesion resin were more effective.

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Diaphragm walls for earth retaining during excavation have recently been used as a permanent component of the main body of a structure in increasing cases because of the advancement in construction technology and for economic reasons. The design method has also been established. When a diaphragm wall is applied as a component of the main body, multiple layers of longitudinal bars are arranged. In order to find a shear design method using such members, a unidirectional static loading test was conducted using beam-type specimens to make an experimental study of shear failure characteristics and shear strength where no shear reinforcement was applied. This paper reports the relationship of the number of layers of longitudinal bars and the reinforcement area to the shear failure characteristics obtained by the test, and proposes a shear strength calculation method.

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In this paper, the mechanisms of the chemical and physical degradation of hardened cement due to acid rain condition were investigated. HNO₃ and H₂SO₄ solution were prepared and blended which referred from the surveying result of rain in Niigata area. The cement paste specimens, carefully cured and sliced as 20×40×2mm, were exposed into the acid conditions. After exposing, Ca(OH)₂, CSH and AFm were measured as the chemical properties. Also, the bending strength and total pore volume were measured as the physical properties of specimen. As the results, the decreasing process of cement hydrates, and the relation between chemical and physical degradation were clarified.

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A new pure-shearing machine for concrete element is developed in the present study. The machine can subject the pure shearing force to concrete element by changing the direction of uni-axial force. Pure shearing strengths of various concrete were tested and correlations between pure shearing strength and other strengths were investigated in this paper. All specimens were fractured from a cleavage failure induced from the vertical crack due to principal stress. The test results indicated that pure shearing strengths of lightweight concrete were higher than tensile strength from the conventional test, which is different from the tendency of normal concrete.

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In order to clarify the seismic behavior of RC rigid frame structures in which the beam was strengthened by externally bonding FRP sheets and steel plates, reversed cyclic loading tests were conducted using RC model specimens. It was found from the tests that the ductility of the RC rigid frame structures was improved by strengthening the beam with FRP sheets. There was a good agreement in the mechanical behavior of such strengthened structures between the tests and analysis using 2D-FEM. In addition, to make clear the influence of strengthening the beam on the seismic behavior of actual structures under strong earthquakes, dynamic response analyses were also conducted.

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In this study, we proposed a method for creep evaluation in high-strength concrete under changing stress at early ages. We used creep recovery ratio obtained from creep tests for estimation of creep behavior accompanying with stress unloading, beside decreased values of precedent sustained stress to consider the stress unloading in applying super position method. Application of the method was examined through a few examples of calculation.

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After the Hanshin-Awaji earthquake, large amount of lateral reinforcement is commonly used to improve seismic performance of the RC structures. Although large amount of and closely spaced lateral reinforcement will be effective to prevent elastic buckling of the axial reinforcement, it can hardly prevent plastic buckling. Therefore, under strong earthquake, axial reinforcement will be subjected to the repeated loading of large deformation reversals ranging from tensile plastic region to compressive buckling region. The authors carried out low cycle fatigue test of deformed bars, and examined the failure criterion of them.

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In this study, both the amount of airborne chlorine and the chloride ingress into concrete were measured for the bridge on the coast in the Sea of Japan. From the results, it has been found that the amount of airborne chlorine has a good correlation with the calculated energy value of waves at the bridge, and that the surface chloride content (Co) indicating the degree of saline environment can be determined based on both the distance from the seashore and the height of structure. Also, it is clarified that the diffusion coefficient for chloride ions (Dc) is not a constant value for the concrete with the same water to cement ratio, which varies depending on the value of Co. Furthermore, the method estimating the chloride ingress into concrete in the bridge was proposed.

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A series of laboratory tests was conducted to evaluate the moisture susceptibility of asphalt mixtures, including moisture damage of asphalt-aggregate bond, and the influence of water immersion on the properties of asphalt mixtures. Furthermore, the effectiveness of various anti-stripping additives was investigated through a variety of tests. It was found that both the asphalt and aggregate types have dominating influences on the moisture susceptibility of asphalt mixtures; hydrated lime slurry is an effective anti-stripping additive for improving the moisture susceptibility; and the net adsorption test, Lottman test and immersed wheel tracking test are effective tools to evaluate the moisture susceptibility.

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The pavement condition assessment (PCA) based on fuzzy set theory is presented. A method to determine membership functions used in PCA is proposed. The effects of inclusion or omission, weight changes and linguistic rating terms' range values changes of pavement parameters on PCA using fuzzy weighted average (FWA) operation are analyzed. The proposed method is compared with the MCI model.
In developing this case, it is found that the proposed method gives more reliable results. Inclusion or omission, weight changes and linguistic rating terms' range values changes of pavement parameters can cause the differences in PCA. The recommendations with respect to PCA using FWA operation are given.

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