Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory project (2) (Contract research)

In Horonobe Underground Research Center construction of underground facility began in 2005 and a construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. Before the HFSC is used as a tunnel support in the gallery, it is necessary to validate that the HFSC is valid under the actual construction condition. The research results in the FY 2007 are as follows. For evaluating corrosion behavior in the HFSC and the durability of the HFSC, reinforced concrete specimen with HFSC 226 have been exposed to off-shore condition in saline water and splashed zone for 6 years and analyzed the corrosion rate and the amount of chloride intrusion. The durability of the HFSC reinforced concrete was assessed to be more than 50 years until cracking due to corrosion is generated. The pH measurements and the analysis of the chemical composition of solid and liquid phase in the HFSC cocrete-water immersion experiments, which were started in the FY 2002, were carried out. Also for the experiments of cement paste for shotcreting, which were started in the FY 2005, were analyzed. Furthermore, results and findings obtained in earlier studies including this study were summarized, and based on those, method of quality control including test method, frequency, standards etc. was suggested. (author)