In July 2016, the “Guidelines on Utilization of Cast-in-Place Concrete with Slump of 12 cm” ( hereafter, “these Guidelines”) went into force for general reinforced concrete structures ordered by the Ministry of Land, Infrastructure, Transport and Tourism. These Guidelines change the standard slump from the 8 cm used for more than a half century to 12 cm. Further, these Guidelines specify the use of self-compacting concrete according to conditions. Evidently, the ultimate goal for concrete work would be completely automated concrete work using self-compacting concrete that does not require manual or mechanical compaction. That said, adoption of the new standard slump value of 12 cm is expected to greatly improve the productivity of concrete work. The “Recommendation for Mix Design of Fresh Concrete and Construction Placement related Performance Evaluation－2016” and the “Recommendation for Mix Design and Construction of Self-Compacting Concrete－2012” were extensively drawn upon as a technical basis for these Guidelines. This paper describes the relationship between these Guidelines and both above-mentioned mix design and construction guidelines.

“Technical Committee on Repair, Rehabilitation and Retrofitting of Concrete Structures over the Limit State due to Deterioration” commissioned by Nagasaki City was established in FY2015-FY2016. Following the designation of Gunkanjima as a historic site of Japan, its coal mining facilities were registered as a World Cultural Heritage component in 2015. For this reason, the Committee carried out various investigations from technological and cultural asset viewpoints concerning conservation measures for remarkably deteriorated reinforced concrete buildings that remain as ruins. In particular, specific repair methods, strengthening methods, and repair work/strengthening work execution methods were investigated with regard to buildings No.3, No.16, and No.65 (south wing). This paper gives an overview of the activities of the Committee.

The possibility of estimating the development of ASR with a new double color staining technique (gel stain method) developed for the purpose of easily revealing the presence and extent of ASR gel in concrete was investigated. This report examines the identification of the presence of ASR and its distribution based on the staining pattern caused by the application of chemicals to the fractured surface of specimens, and the relationship between the staining characteristics and the expansion process. The distribution of ASR gel inside and around coarse aggregate and fine aggregate particles was clarified using a digital microscope to examine the fracture surface coated with the chemicals in greater detail. As a result, it was found that the presence and extent of ASR can be determined from the staining characteristics of the fractured surface of concrete coated with chemicals.