In November 2022, the Architectural Institute of Japan published a new edition of JASS 5 that has been greatly revised and more clearly positioned to reflect the many changes that have taken place over the thirteen years from 2009 to 2022. These changes include changes in social conditions, and advances in materials used, construction technology and quality control methods, as well as amendments of applicable laws and regulations in the field of reinforced concrete work. The revisions were made toward the promotion of resource recycling and a low-carbon society, the rationalization and efficiency improvement of construction and quality control through digital transformation（DX）, and the realization of higher performance and higher quality concrete. This commentary introduces the main revisions of JASS 5.

To reduce the weight of the exterior PC plates, a thin exterior SFRC plate was developed. Until now, exterior SFRC plates have had issues in terms of economic efficiency and fire resistance. In this development study, the concrete mixture design was optimized to ensure the same performance as conventional concrete with a smaller amount of fiber for higher economic efficiency. Structural performance as an exterior curtain wall construction method was confirmed for the mixture design, and the fire resistance performance of exterior walls using this method was verified. For the rationalization of the fire resistant covering of adjacent steel structural members, we developed also a synthetic fire-resistant covering method that integrates exterior SFRC plates, and we obtained ministerial certification for its application to fire-resistant structures. The results obtained were applied to an actual building.

Surface observation and component analysis were conducted on rebar obtained from a 48-year-old reinforced concrete building under an environment with airborne salt in order to estimate the cause of their deterioration. Measurements included surface observation by microscope and SEM, as well as component analysis by EDS, XRD/XRF, and EPMA. Although the details of the building were purposefully concealed at the time of testing during surface observation and analysis of the specimens, a comprehensive examination of the results of each test made it possible to infer that the corrosion of rebar may have progressed due to airborne salt and carbonation, rather than internal chloride. Furthermore, although this was limited to a single case, the authors were able to show the shape and component distribution of corrosion product under an actual exposure environment.