[en] In Horonobe Underground Research Laboratory (Horonobe URL) Project, construction practicality test with HFSC (Highly Flyash contained Silica-fume Cement) is planned in a part of the gallery. Before HFSC is placed in the gallery, it is necessary to check that HFSC has performance as tunnel support under the actual construction. The research results in 2008 were as follows. For liner concrete of shaft in Horonobe URL, 4 types of mix proportion suggested for ordinary concrete and high strength concrete which contains polypropylene fiber or not. As early age strength, 5N/mm² is required because of concrete formwork. HFSC424 with low water binder ratio can fulfill this requirement in combination with super plasticizer. On laboratory tests in lowering behavior of pH in HFSC concrete, the pH of immersion fluid was measured and components of the immersion fluid and the solid phase were analyzed using test specimens in a long-term immersion test which had been continued since 2003. An experiment which investigates dissolution of HFSC cement hydrates to ground water around Horonobe URL was carried out. According to the experiment, dissolving depth of HFSC is 1/4 compared with the depth of Ordinary Portland Cement hydrates after 90 days. (author)