This paper discusses the effectiveness of zinc anode cathodic protection applied to RC beam specimens severely damaged by chloride attack. Based on the experiment, that is, the zinc anode cathodic protection is applied to the 41-year-old RC beam specimens exposed to natural marine environments, suitable application method of zinc anode is discussed. In the experiment, repair was performed in three stages. In the first stage, polymer-modified mortar was cast to replace existing concrete in the middle tensile part with zinc anodes embedded in the repair mortar. After protective current became stable value, the anodes were disconnected from steel bars for a year defined as the second stage. During the one year of second stage, the steel bar in the repair area remained be passive state, without any sign of corrosion. As for the third stage, additional zinc anodes were installed in the existing concrete part in order to protect the steel in old chloride contaminated concrete. From one-year observation after the application of zinc anodes in old concrete part, it is confirmed that “time lag application” could stop the corrosion of steel bar in both parts.

Concrete structure is usually inspected by appearance at the periodical inspection. However, highly skilled engineers are necessary for this preliminary and qualitative inspection. Considering decrease in expert and increase in deteriorated concrete structures, more quantified inspection method is needed to evaluate the performance more accurately and easily. Previous researches have presented the relationship between corrosion mass loss of reinforcing steel bar in concrete and surface crack width. These studies were often conducted by using reinforced concrete specimen which includes single longitudinal rebar. On the other hand, on-site structures include not only longitudinal rebar also transverse rebar which is located with larger cover thickness. For this reason, the accelerated corrosion test using the specimens and inspection at an on-site corroded structure were conducted to evaluate the effect of the transverse rebar and its corrosion on the behavior of surface crack. As a result, it was revealed that internally propagated crack would have a large influence on the surface crack and the index of the surface crack density could bring more accurate evaluation of the corrosion mass loss of rebar than only the crack width.

Experimental studies were conducted to clarify mechanisms of corrosion inhibition of rebar by steel fibers in steel fiber reinforced concrete, SFRC. Test specimens with an artificial crack were made from concrete and SFRC, and steel fibers were arranged in the crack for some of concrete specimens. Specimens were exposure under wet-dry cycle and salt water were poured through the artificial crack when wet condition. After prescribed cycles, rebar corrosion was evaluated and impacts of steel fibers on that were discussed. As the results, it was confirmed that steel fibers inhibited the rebar corrosion, and its effect was appeared when fibers existed in the artificial crack mostly. The corrosion inhibition was shown for large crack specimens as well as small crack ones. An electrochemical factor due to corrosion of steel fibers themselves was supposed as main mechanisms of corrosion inhibition from the experimental results.

In this study, we investigated the shrinkage and compressive properties of polymer-modified mortars using redispersible polymer powders in the range of the P/C of 10% or less at the W/C of 35% and the S/C of 1.0. As a result, Autogenous shrinkage strain after deforming of polymer-modified mortars using acrylic redispersible polymer powders was almost the same regardless of the P/C. The acrylic redispersible polymer powders affected the drying shrinkage component of polymer-modified mortars. Drying shrinkage strain of polymer-modified mortars increased with increasing the P/C. Mass loss of polymer-modified mortars varied depending on the redispersible polymer powders used and its quantity. Compressive strength and Young's modulus of polymer-modified mortars tended to decrease with increasing the P/C. The effect of redispersible polymer powders on the compressive strength and Young's modulus of polymer-modified mortars was not so large. Poisson's ratio of polymer-modified mortars using acrylic redispersible polymer powders was about 0.2 regardless of the P/C.

In order to establish a safety evaluation technique for ASR-deteriorated structures, crack observation, observation of ASR expansion such as reinforcing bar strain and concrete strain, and loading tests were conducted on RC beam specimens with ASR deterioration to evaluate the effects of ASR deterioration on the RC beam members. In addition, X-ray computed tomography (CT) images of core concrete taken from these RC beam specimens were taken to evaluate the cracking conditions in the ASR concrete. The test results showed that the ASR cracks in the specimens without shear reinforcement opened further under loading and cracks were generated, leading to shear failure. In addition, many fine cracks parallel to the loaded cracks were observed in the cores taken from the ASR specimens.

The X-ray diffraction method has been already established as one of the most effective nondestructive evaluation method of a stress in crystalline materials. Since white X-ray beam has a wide wavelength range, a diffraction angle has to fix during a measurement to obtain a lattice spacing using the Bragg’s low. Therefore, the white X-ray method has some different features from the characteristic X-ray method. For example, the information of lattice spacing of many lattice planes in a material can be obtained simultaneously on the same diffraction angle. Because all equipment are held fixed position during a measurement, it is advantageous to in-situ measurement under the special environment such as high temperature or high pressure. In the present review article, a brief history of development of the white X-ray method is covered and some factors related to the measurement accuracy is explained. Fundamentals of the measurement system using white X-ray and the energy dispersive method are presented. Applications of the method using white X-ray obtained from a rotating target type X-ray generator to the measurement of residual stress of a surface ground material and a coating material are described. Furthermore, applications of the method using high energy white X-ray generated in the synchrotron radiation facility SPring-8 to the measurement of internal strain of a material loaded by four-point bending and strain distribution in the vicinity of crack tip in a material introduced a fatigue crack are also described.

Residual stresses in astresses in small-bore butt-welded pipe of austenitic stainless steel have never been measured. It is difficult to obtain a detailed residual stress map of the root welded part, because the gauge volume in neutron diffraction is large. The stress evaluation of the welded part by synchrotron X-rays was also difficult due to the dendritic structure. In this study, a double exposure method (DEM) with high-energy synchrotron X-rays was applied to measuring the details of the residual stress of the welded part, and we succeeded in obtaining the detailed axial and radial stress maps of the root welded part of the plate cut from the welded pipe, though the stress map was under the plane stress condition. The hoop stress map of the butt-welded pipe was obtained using the strain scanning method with neutrons under the triaxial stress state. The axial and radialradius stress maps under a triaxial stress state were made up using the complementary use of the synchrotron X-rays and neutrons. As a result, the detailed stress maps of the root welded part of the butt-welded pipe were obtained. The result of the actual stress analysis sufficiently explained the initiation and propagation of SCC.

The stress in polyphenylene sulfide (PPS) resin reinforced by glass fibers of 26 mass% was measured by the diffraction method using synchrotron with energy of 18 keV. The stress in the matrix was determined by the sin2ψ method with iso-inclination optics of transmitted X-ray diffractions. Tensile coupon specimens were cut from the skin-layer of injection molded plates in three directions, parallel, perpendicular and 45°, to the molding direction. The matrix stresses in the loading and transverse directions of specimens were measured under several uniaxial applied stresses. They changed proportionally to the applied stress. The proportional constants of the matrix stresses to the applied stress were determined, and named the stress-partitioning coefficients. The elastic constant and the matrix stress of the composite were calculated theoretically using micromechanics for two cases of fiber orientation: unidirectional (UD) and varied orientation distribution (VD). Fiber orientation tensor was determined from microscopic measurement of the cross-sectional shape distribution of fibers. Compared with the calculation based on UD fiber orientation, the analytical values based on micromechanics considering the variation in fiber orientation are closer to experimental values of elastic constants and stress-partitioning coefficients.

Magnesium hydroxide layer improve corrosion resistance of magnesium alloys. Nonuniform strain on magnesium alloys surface was reported that affected to layer formation and corrosion resistance properties. Hydroxide layer formed to high pressure die cast ASTM AZ91D magnesium alloy, then investigated to correlation between hydroxide layer formation and residual stress and strain distribution on alloy surface which were measured by X-ray. Strain distribution was evaluated by full width half maximum (FWHM) value. Formed hydroxide layer was well compatible with FWHM distribution in as cast specimen. Heat treated for homogenization was carried out to inspection for correlation FWHM. FWHM was significantly lowering by heat treatment. Hydroxide layer tends to thin where FWHM value was low, therefore correlation between nonuniform strain and hydroxide layer formation was found out.

The technology of multilayer thin films to improve performance is widely used in the fields of semiconductors and functional composite materials. However, each layer of the multilayer film generates a residual stress during deposition due to differences in Young's modulus and coefficient of thermal expansion. In addition, the residual stress of the coating material is significantly affected by the mechanical load during use. In this study, the coated materials with deposited multilayer thin films were subjected to repeated bending loads, and the effects on the residual stresses in the thin films and substrates were investigated. Carbon steel (JIS: S45C) was used as the substrate material for the specimens. The thin films were deposited by sputtering. Three kinds of specimens were used, in which Cu, TiN and SiO₂ films were deposited as a single Cu layer, a Cu/TiN double layer and a SiO₂/Cu/TiN multilayer. The residual stress values of the Cu layer within the thin films were evaluated by X-ray stress measurement method using 311 and 222 diffractions of Cu. As a result, the tensile residual stress values in the Cu layers within each thin film were approximately 60~70 MPa for the single layer and 110~120 MPa for the double and multi-layer films. The residual stress values in the substrate, carbon steel, were evaluated using 211 diffractions of α-Fe. As a result, a tensile residual stress of about 30 MPa is existed. When all the coated materials were subjected to repeated bending loads, the change in the residual stress values of Cu layer showed that the residual stresses relaxed rapidly after several cycles of repeated loading and saturated to a value of about 30 MPa after 100 cycles. On the other hand, the residual stress evaluation by 222 diffractions of Cu showed that for all coated materials the residual stress values increased and decreased repeatedly with increasing number of repeated loadings. For the carbon steel substrate, the residual stress values hardly changed due to repeated loading.

In order to develop a new concrete repair method under cold and moist conditions, melt adhesion tests of carbon fiber sheet and cement mortar using thermoplastic epoxy resin were examined. Thermoplastic epoxy resins having controlled molecular weight were prepared by the addition of bisphenol A. Melt viscosity and tensile properties of the epoxy resins decreased with decreasing molecular weight. Higher adhesive strength was observed when the lower-molecular-weight resin was used. It was shown that the low melt viscosity of the epoxy resin plays an important role on achieving strong adhesion between carbon fiber sheet and mortar.