In December 2021, the Subcommittee on the Revision of Guidelines for High Fluidity Concrete of the Architectural Institute of Japan revised the “Recommendations for Mix Design and Construction Practice of High Fluidity Concrete” established in 1997 for the purpose of popularizing, standardizing and systematizing high fluidity concrete in the construction field. This paper describes the background to the revision of these Recommendations, the contents of the study, and the outline of the revision of this guideline. It is hoped that these Recommendation will help further disseminate and improve the quality of high fluidity concrete technology.
The Tohoku Regional Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism has formulated the “Guide for Ensuring the Quality of Concrete Structures（Draft）”（for bridge abutments, bridge piers, culverts, and retaining walls） and the “Guide for Ensuring the Quality of Concrete Structures（Draft）”（for tunnel lining concrete） for new structures in order to ensure the quality of concrete structures for reconstruction roads, where a large number of structures are constructed in a short period of time. Both of these guides adopt a quality assurance system that aims for proper placing and compacting of concrete by using the “Check Sheet to Grasp Construction Conditions”. After formwork removal, inspection for defects is conducted and the type and severity of detected defects are evaluated by visual evaluation of the surface layer, and the construction method for the next lift is improved to suppress the occurrence of similar defects. The following is an explanation of the points to note regarding the use of these guides.
In response to the Japanese government’s carbon neutrality declaration, efforts toward carbon neutrality are accelerated in various industry sectors. In the field of cement and concrete, carbon recycling technology has been attracting attention as one of the approaches to reducing CO2 emissions, and CO2 absorbent concrete, which can reduce the amount of cement used and absorb and fix CO2 while achieving the same strength from carbonation curing as conventional products by the time of shipping, is now in practical use. This paper reviews the development and demonstration of carbonating additive, a key material for CO2 absorbent concrete, and describes the characteristics obtained from carbonating curing and the knowledge obtained thus far.
Although rebar arrangement inspection is an important part of the construction process, the preliminary preparations to be made for the series of inspection tasks, the inspection work itself, and the preparation of reports require a lot of time and effort. The authors have begun developing a rebar arrangement inspection system using stereo cameras and AI technology, and this system is currently being used at many sites. Further, the system was adopted by the Ministry of Land, Infrastructure, Transport and Tourism（MLIT） as part of the “Public/Private R＆D Investment Strategic Expansion Program（PRISM）,” which supports “projects related to the introduction and utilization of innovative technologies to dramatically enhance productivity at construction sites.” Trial application of this technology at actual construction sites earned it a rating of A for highly promising introduction effects and high feasibility of implementation in society. In anticipation of the further spread of this system in the future, the authors have developed heretofore unavailable functions for lower layer rebar arrangement measurement, wide area measurement, and sheath pipe measurement.