The authors proposed a " Curing planning method based on cement hydration analysis " based on the curing concept in the current Standard Specifications for Concrete structures of Japan Society of Civil Engineers. Furthermore, as improving the productivity of concrete work has become an issue, simply identifying curing conditions to ensure performance is insufficient, and so we proposed a "Curing plan formulation method that takes into account both productivity and performance". In order to promote the practical implementation of these proposed methods, we considered developing a " Support system for creating curing plans " that can create curing plans and calculate nominal strength correction values that take productivity improvement into account without performing cement hydration analysis. This report provides an overview of the curing planning method based on cement hydration analysis, the curing plan formulation method that takes into account productivity and performance assurance, and the support system for creating curing plans.

Water is required for the corrosion of reinforcing steel bars in reinforced concrete. Therefore, it is important to clarify the permeability of concrete. Several studies have reported that concrete with blast furnace slag cement exhibits high water permeability resistance. However, the mechanisms of superior water permeability resistance and the effects of carbonation remain unclear. This study compared the permeability of the concrete core and specimens with blast furnace slag cement Type C. As a result, it was found that permeability is affected by the moisture content of concrete. Furthermore, it was found that water permeation resistance decreases indoors without water supply compared to outdoors.

This study aims to develop a non-shrink mortar that cures properly under freezing conditions around −10°C without requiring heating or insulation. Mortars containing lithium nitrite (LN) were evaluated for strength development and expansion-shrinkage behavior when cured at −10°C immediately after mixing. Aluminum powder was also added to enhance non-shrink performance. To assess field applicability, outdoor exposure tests using specimens simulating bridge bearing mortar under freezing conditions were conducted. The results showed that adding LN at 4% or more prevented initial frost damage and allowed adequate strength development despite temperature fluctuations. Aluminum powder effectively induced slight expansion, compensating for shrinkage and ensuring dimensional stability. Even when temporarily exposed to temperatures below −10°C shortly after placement, the mortar exceeded the required compressive strength after 28 days and maintained dimensional stability. These findings suggest that the developed non-shrink mortar can be applied in cold environments without costly heating or insulation, offering a practical solution for cold weather construction.

The interfacial transition zone surrounding aggregates plays a crucial role in the strength and fracture behavior of concrete. Previous studies have primarily relied on surface observations of specimens to investigate cracking around coarse aggregates, leaving the three-dimensional internal mechanisms of compressive deformation and fracture unclear. To address this issue, the authors developed an X-ray CT system capable of imaging under loading conditions and applied digital image correlation to visualize internal strains in three dimensions. In this study, this system was used to examine the three-dimensional deformation of a specimen containing a high-strength mortar sphere embedded as a model aggregate. As the results, interfacial voids and transition zones ranging from 0.1 to 1.5 mm were identified. When the applied compressive stress exceeded the apparent critical stress, image measurement showed that expansion strain increased on the side surface after microfractures developed at the upper and lower interfaces of the sphere, ultimately leading to failure. And the local strain distribution around the interface extended approximately ±2 mm.

A cement-based material, when used as an electromagnetic wave absorber, offers excellent weather resistance against rainwater and UV rays. However, since cement-based materials are porous, their moisture content is a concern because it can affect the electromagnetic wave absorption performance. In this study, we conducted experiments focusing on the water-cement ratio and the addition rates of polypropylene pellets (a dielectric material) and carbon powder (a resistive material) to suppress the effects of moisture content on electromagnetic wave absorption performance. The results showed that by setting the water-cement ratio at 30%, the polypropylene pellet content at 32%, and the carbon powder content at 6%, stable electromagnetic wave absorption can be achieved despite changes in moisture content.

Several hypotheses have been advanced to explain the mechanism of scaling in concrete subjected to freeze–thaw cycles in chloride rich environments, with the prevailing view being that scaling arises from the combined effects of multiple processes. The present study was undertaken to contribute to a more comprehensive understanding of this phenomenon by examining, in detail, the strain distribution of mortar and concrete during freeze–thaw cycles. Experimental results corroborated previous findings regarding the effects of chloride concentration in the immersion solution, air content, and water cement ratio on the severity of scaling. It was further observed that, at subzero temperatures, the coefficient of thermal expansion of mortar/concrete was approximately twice the conventional value, a behavior that can be attributed primarily to the thermal expansion properties of ice. In contrast, EPMA analyses revealed negligible chloride penetration into the mortar, indicating that the contribution of chloride to scaling is confined to the near-surface region. On the basis of these findings, it is proposed that, in addition to mechanisms previously identified in the literatures, the influence of the thermal expansion coefficient of ice should be considered as a governing factor in the development of scaling.

This study explores the impact of mix proportions and CO₂ concentration during carbonation on the microstructure and mechanical properties of mortar containing ordinary Portland cement, ground granulated blast furnace slag, and powder predominantly composed of γ-phase dicalcium silicate. Mortar specimens were analyzed using compressive strength tests, mercury intrusion porosimetry, and thermogravimetric-differential thermal analysis. Key findings include: 1) minimal calcium carbonate formation and no improvement in microstructure or strength when the γ-C₂S-based powder replacement ratio was 0% or 10%, regardless of CO₂ concentration; 2) significant densification and strength enhancement when the γ-C₂S-based powder replacement ratio exceeded 30% and CO₂ concentration was above 30%; 3) a strong correlation between pores larger than 50 nm and compressive strength even after carbonation; 4) consistent pore refinement with increasing calcium carbonate content, independent of mix conditions or curing age. These results suggest that optimizing the γ-phase dicalcium silicate content and carbonation conditions can enhance the durability and performance of cementitious materials, contributing to the development of sustainable construction technologies.

Deterioration mechanisms such as alkali–aggregate reaction, chloride attack, and carbonation significantly affect the quality and durability of concrete. To address these issues, Japanese companies and organizations have undertaken a variety of initiatives. While numerous proposals and recommendations have been made in academia and disclosed through publications such as research papers, the trends in technological development within the industrial sector remain largely unexplored. This study analyzes technologies aimed at mitigating concrete carbonation by examining patent information, with the goal of clarifying industrial development trends. The findings reveal eight key insights: 1) the construction, cement, and chemical industries are actively engaged in addressing concrete carbonation; 2) industries that began filing patent applications early have made substantial contributions to problem-solving; 3) there is strong demand for technologies that prevent carbonation, enable mending or reinforcement, and facilitate deterioration assessment and diagnosis; 4) the chemical and paint industries are particularly active in specific technical domains; 5) technologies related to “Mending and Reinforcement” and “Survey and Deterioration Diagnosis,” which have seen increasing patent activity in recent years, are expected to be developed primarily by the mending industry and research institutes; 6) for the technologies examined in this study, changes in patent fees have minimal impact on patent duration; 7) technologies involving admixtures and binding materials tend to have longer lifespans; and 8) there are notable differences in technology life expectancy depending on the intended purpose.

While non-destructive testing (NDT) is applied for process control during 3D concrete printing (3DCP), systematic quality assessment of hardened printed structures is still underdeveloped. The layered structure of 3DCP can introduce anisotropic defects, such as inter-filament voids, which critically affect the mechanical performance and structural integrity. Therefore, a reliable NDT method for internal quality assurance is essential. This study investigates the applicability of elastic wave tomography (EWT) for these purposes. First, specimens with controlled inter-filament void structure were fabricated by modifying printing parameters. The influence of input wave frequency on internal void detection was systematically examined by applying impacts with steel balls of different diameters. Furthermore, the progressive fracture behaviour under compression was monitored sequentially, with EWT performed at pre-peak load steps and digital image correlation (DIC) capturing the surface strain field. Results demonstrated that EWT can effectively visualise the presence and distribution of internal voids. However, detection sensitivity and spatial resolution were found to be strongly dependent on the input frequency. Lower frequencies excelled at identifying widespread, low-quality zones by averaging material properties, while higher frequencies offered greater potential for localising discrete voids. In compressive testing, EWT captured crack propagation and visualised fracture progress. The detected area showed good agreement with the strain field obtained from DIC, demonstrating that EWT is capable of monitoring the fracture progression.

The maintenance of concrete structures is challenging owing to the corrosion of reinforcing steel bars. The expanding pressure caused by corrosion leads to corrosion-induced cracking. Several studies have investigated the relationship between surface cracks and the mass loss of steel bars to establish efficient techniques for predicting mass loss in steel based on cracks. However, the effects of voids around steel bars on the cracking and corrosion of steel bars remain underexplored. This study evaluates these effects using X-ray imaging. Mortar specimens reinforced with an axial steel bar were prepared; the steel bar was corroded using the impressed current technique. X-ray imaging was used to visualize the corrosion products filled in the voids around the steel bar. The propagation of cracks eventually diminished because of the voids in the early phase of corrosion. In addition, as the cracks progressed due to corrosion, the influence of voids around the steel bar became less pronounced.

Deck slabs of highway bridge have been deteriorated due to traffic wheel-loads and environmental factors. To improve the durability of highway bridge slabs, overlaying with steel fiber reinforced concrete (SFRC) are generally implemented. However, in recent years, it is occasionally observed that the overlaying SFRC layer are prematurely de-bonded from the substrate of existing reinforced concrete (RC) slabs. The delamination prevention of the overlaying materials is needed to ensure fatigue durability of the repaired bridge deck slabs. Hence, the study aimed at improving the adhesion of covering layer. In particular, the study focused on the applicability of thin-layering with high-performance fiber reinforced mortar (HPFRM). Direct tensile and shear tests were conducted to examine the peeling resistance of the HPFRM. The experimental study revealed that the bond-strength development at early age is significantly affected by the hardening rate of the adhesive.

This study aims to reveal the mechanism of mud film formation when bentonite-based slurry and polymer-based slurry infiltrate into soil pore spaces by comparing the infiltration characteristics of both slurry with different properties. While most of the previous drilling slurry research has focused on macroscopic phenomena, it is important to closely observe microscopic phenomena in mud film formation to truly achieve the objective. Therefore, this research group succeeded in visualizing and quantifying the bentonite inside the specimen, which could not be seen by previous SEM studies, by a bentonite-based slurry infiltration test, X-ray CT imaging, and image analysis. In this study, a polymer-based slurry, which had not been investigated before, was also used. The results suggest that the total volume of bentonite may be smaller and the ratio of smaller clusters may increase with more viscous drilling slurry with higher CMC concentrations. In addition, while bentonite-based slurry reduces permeability through mud film and clusters inside the specimen, polymer-based slurry does not form a clear mud film and reduce permeability mainly through viscosity.

Ultrasonic vibration is applied to a part of the mold in Resin Transfer Molding (RTM) to promote macroscopic resin flow and resin impregnation into fiber bundles. RTM has been attracting much attention to produce FRP products, because the amount of capital investment required is relatively small compared to autoclave molding method and it does not require special skills like hand lay-up method. The quality of RTM products is highly dependent on the resin impregnation into fiber preform during the mold-filling stage, and it is required to avoid the creation of molding defects such as dry spots and voids. In this study, the experimental setup is designed to apply ultrasonic vibration to a part of the RTM mold, and its effect on resin flow and impregnation is investigated. It was found that ultrasonic vibration could assist resin impregnation into fiber bundles and promote localized resin flow. Furthermore, based on resin impregnation monitoring using ultrasonic testing it was confirmed that ultrasonic vibration could improve final state of resin impregnation. The effect of vibration intensity is also discussed through microscopic observations and thermographic measurements.

Recently, advanced CFRTPs have begun to be used as lightweight structural materials in aircraft and some mobility products due to their high mechanical properties and productivity. However, it is not widely used in general products due to the high intermediate material and manufacturing costs. Therefore, it is necessary to develop an innovative technology to manufacture CFRTP products at low cost. As an effective way to meet this challenge, a hybrid insert injection molding technology was developed in this study. This method achieves complex shape formability by combining injection molding and pultrusion methods. When six CF/PP pultruded wires were arranged in a grid structure and inserted into a mold to over-mold PP, the molded product showed significant warpage. In this study, warpage deformation mechanism was investigated by experiments and finite elemental simulation, and some restrain methods were tried, thus realized by experiment. As a result, it was found that the difference in thermal shrinkage rate between CF/PP and PP was the cause of the deformation. It was also found that this manufacturing method required inserting a flat lattice structure in the center of a symmetrically shaped product to restrain the deformation. To meet this requirement, a symmetrical shaped mold for injection molding and a locally heating compression forming method for intersection of the wires to manufacture a flat grid structure were developed. As a result, using the mold and pre-forming method, the deformation was reduced by 79.2%. Finally, a stable insert injection molding process was established.

The objective of this study is to improve the efficiency of identifying fracture initiation points in tempered glass by utilizing an integrated system that combines an optical system and image processing techniques. Tempered glass enhances its mechanical strength by inducing compressive stress on its surface. Traditionally, the identification of fracture initiation points in tempered glass depends on manual inspection, which is both time-intensive and reliant on the inspector's experience. To address these challenges, we developed a system that incorporates an optical system for uniform illumination using a light guide plate along with a robust image processing workflow. The workflow includes dark subtraction, binary thresholding using Otsu's binarization method, and contour extraction with the Suzuki85 algorithm. Additionally, polygonal approximation of the contours was performed using the Douglas-Peucker algorithm, with an experimentally determined optimal tolerance value of 4.1%. By analyzing fragment characteristics such as the number of vertices, convexity, area, and aspect ratio, the system was able to identify potential initiation fragments based on criteria derived from experienced fractography inspectors. Experimental validation was conducted using ten tempered glass panels, each fractured under controlled impact conditions to ensure consistency. The developed system successfully reduced the number of fragments that inspectors need to investigate to approximately 10% for the group of fragments arranged with the in-plane direction facing upward within the capture screen. This study demonstrates the practical feasibility of integrating optical and image processing technologies to automate and enhance tempered glass fracture analysis. The proposed system has potential for adaptation to other materials and industrial applications.