The “Recommendation for Mix Design and Construction Practice of Concrete Filled Steel Tubular Structure” was established as a supplement to the section on concrete for filling steel tubular structures in JASS 5 “Japanese Architectural Standard Specification for Reinforced Concrete Work” of the Architectural Institute of Japan. This “Recommendation” presents the latest knowledge on concrete for filling steel tubular structures and the rational mix design and construction methods existing at the present time. In addition, in consideration of the view that bleeding tests to verify the quality of concrete are complicated to carry out, it proposes ways to rationalize such testing, along with other improvements. This report presents an outline of the above.
To clarify the mechanisms of deterioration, numerous studies have been conducted using SEM-EDX, X-ray diffraction, EPMA, and so on. However, many aspects of deterioration mechanisms still remain to be elucidated. In addition to the above analyses, the authors are also investigating the use of Raman spectroscopic analysis. This report explains the principle of Raman spectroscopy and introduces the application of Raman spectroscopy to the evaluation of the corrosion products of iron, which is a metallic material, and aggregate, which is an inorganic material. Furthermore, the authors propose a deterioration index using Raman spectroscopy based on the phenomenon of the increase of fluorescent substances when organic surface coating materials deteriorate.
This paper introduces a self-healing technology for cracks in concrete that was developed for the purpose of ensuring durability and extending the service life of concrete structures through the metabolic activities of bacteria. This technology mixes in a self-healing material composed of a special strain of the Bacillus genus and polylactic acid, which is a source of food for these bacteria, during the production of concrete. When cracks occur in the concrete after hardening, the bacteria decompose the polylactic acid, causing the precipitation of calcium carbonate, which can close cracks up to 1 mm wide. The sustainability effect of this technology was evaluated from three aspects: social, economic, and environmental. As a result, it was found that products based on this technology can greatly contribute to the creation of a sustainable society as construction materials for infrastructure and buildings.