This paper focuses on the corrosion of reinforcement buried in concrete mixed with seawater, based on seawater-mixed concrete research trends. In particular, the paper explains the influence of the use of seawater for concrete mixing on the long-term durability of concrete based on test results and existing research data such as long-term exposure tests, and it summarizes the current state of knowledge with regard to corrosion suppression method and the use of reinforcing materials other than carbon steel for concrete mixed with seawater. While mixing concrete with seawater tends to carry a negative image, the authors hope that this paper will contribute to the proper use of such concrete based on academic and engineering judgment as research advances are made.

In March 2016, three important public notices related to JASS 5 were amended. The notice on materials used was amended to allow the use of eco cement and recycled aggregate H. The notice on the removal of formwork was amended with additions including a method to determine the timing of removal of sheathing according to the temperature of concrete after placing. The notice on concrete strength was amended to allow management of the concrete strength of structures with standard cured specimens, besides conventional core specimens, on-site water cured specimens, on-site sealed cured specimens, and so on. This report describes the revised 2018 edition of JASS 5 along with the above public notice amendments.

More than 20 million centrifugal compaction concrete poles used as support for power distribution lines and communication lines have been installed nationwide in Japan. The authors conducted a study on progress prediction of crack width with the aim of improving the efficiency of inspection of such concrete poles as part of their maintenance. Material testing of centrifugal compaction concrete specimens was carried out and strength characteristics, creep characteristics, and drying shrinkage characteristics were analyzed. In addition, continuous loading was carried out using actual poles, and crack dispersibility, crack width, reinforcement strain, and deflection trends were measured. From these results, we summarized the characteristics of centrifugal compaction concrete for each component of the crack width calculation formula, and we propose a calculation formula simplified for application to inspection work.