The purpose of this study is to formulate an estimation method for airborne chloride in consideration of wind conditions and surrounding topography. The relation between wind conditions from AMeDAS or MSM (Meso Scale Model) and the amount of airborne chloride was studied. As a result, it was confirmed that the amount of airborne chloride is proportional to the square of wind velocity when the wind velocity is 4 m/s or higher. Because the frequency of the square of wind velocity of 4 m/s or higher calculated by a statistical method using Box-Cox transform follows a normal distribution, the sum total value of the square of the wind velocity for one year was estimated by interval estimation. Furthermore, the estimation of the amount of airborne chloride was performed in consideration of the surrounding topography using LightGBM, which is an algorithm for machine learning. The estimation results generally agreed with the measured values. Further, the influences of the surrounding topography on the amount of airborne chloride were visualized by using SHAP values.

Three-component concrete made using blast furnace slag cement with admixture of silica fume has been reported to greatly improve chloride penetration resistance, and its broader use is desired. In this study, silica fume slurry is post-added to concrete in a truck agitator, the concrete is further agitated, and the fundamental properties of the resulting concrete are examined. As a result, it is found that the chloride diffusion coefficient of the concrete is lowered by post-addition of silica fume slurry. This suggests that it is possible to produce three-component concrete with post-addition of silica fume slurry in a truck agitator.

A three-year exposure test was conducted in a simulated marine environment and in a simulated splash zone to evaluate the performance of concrete with expansive additive in a marine environment. The test parameters were the presence/absence of expansive additive, the grade of the restraining bar ratio, and the water-cement ratio, and the results were compared and verified in terms of physical properties and microscopic observation. As a result, it was confirmed that the performance of the concrete with expansive additive in a marine environment was almost the same as that of concrete without expansive additive. However, it was found that the effect of the restraining bar was remarkable in the evaluation, and appropriate evaluation taking into consideration the actual structure was necessary.

In seismic retrofitting of existing reinforced concrete structures, additional members are generally connected to existing members by using post-installed anchors and a roughened concrete surface. To date, however, little research has focused on these hybrid joints. In this study, shear loading tests on hybrid joint specimens under combined stress were conducted. In addition, the shear strength formula and the mechanical model of the roughened surface were proposed based on the authors’ previous findings. As a result, it was found that the shear strength of the roughened surface under combined stress can be properly evaluated. Moreover, the mechanical behavior was reasonably estimated by combining the proposed model and the authors’ previous dowel model.

A precast culvert with arcuate corners was designed for the purpose of reducing the amount of reinforcement and the production cost. By changing the shape of the corners from rectangular to arcuate, the bending moment was reduced by up to 45% compared with the normal rectangular shape in the trial design. As a result, a reduction in the amount of reinforcement of up to 40% was achieved. To confirm the performance when reversed cyclic loads are applied during an earthquake, performance verification tests were conducted on the corners. The load carrying performance was confirmed to exceed the value calculated by frame analysis, and the deformation capacity was found to satisfy the design codes. This paper describes the design outline, the results of the performance verification test and its analysis.

Stainless steel rebars are a type of highly durable steel. Their mechanical properties such as yielding behavior and strain hardening are different from those of ordinary steel rebars. In this paper, to determine the applicability of stainless steel rebars to concrete highway bridges, the bending performance of beam members made of stainless steel rebars was evaluated by bending loading tests and fiber element analysis. Comparison of stainless steel reinforced concrete beams with ordinary reinforced beams showed that yield behavior and strain hardening had little effect on member behavior, there was no significant difference in the load-bearing capacity curves, and members using stainless steel rebars had similar bending performance to that of members using ordinary steel rebars when used for a highway bridge.

The glass bead preparation method specified in JIS R 5204 for X-ray fluorescence analysis of cement and the calibration curve method specified in JIS A 6201 for the XRF-briquette method were applied to five types of fly ash, and the SiO₂, Al₂O₃, Fe₂O₃, Na₂O, and K₂O content was determined at four measuring institutions with three repetitions per sample. Although some laboratories need to review the procedure for glass bead preparation and improve the calibration curve setting accuracy for quantitative analysis using the XRF analyzer in order to improve the analysis accuracy, relatively high analysis accuracy was secured even when the briquette sample was replaced by the glass bead sample in the XRF analysis method of JIS A 6201. It was confirmed that the analysis of each of the Al₂O₃, Fe₂O₃, Na₂O, and K₂O components along with SiO₂ is possible with relatively high analytical precision even when the briquette sample is replaced by a glass bead sample in the JIS A 6201 XRF analysis method.