Basic properties of the concrete using the low alkaline cement (HFSC) developed by JAEA

The cementitious materials are used as candidate materials for the tunnel support of the deep geological repository of high-level radioactive wastes (HLW). Generally the pH of leachate from concrete mixed Ordinary Portland Cement (OPC) shows a range of 12 to 13. The barrier function of bentonite used as a buffer material and that of host rock might be damaged by the high alkaline leachate from cementitious materials. Therefore, low alkalinity that does not damage each barrier function is necessary for cementitious materials used for the tunnel support system of the HLW geological repository. Japan Atomic Energy Agency has developed a low alkaline cement named as HFSC (Highly Fly-ash contained Silicafume Cement) which the pH of the cement leachate could lower approximately 11. We have confirmed the applicability of HFSC for the tunnel support materials, by using experimentally as the shotcreting materials to the part of gallery wall at 140 m, 250 m and 350 m depth in Horonobe Underground Research Laboratory. And moreover, HFSC has been used as the cast-in-place concrete for the shaft lining concrete at the depth of 374 m-380 m. This Data/Code summarized the past HFSC mix proportion test results about the fresh concrete properties and hardened concrete properties, in order to offer the information as a reference for selecting the mix proportion of HFSC concrete adopted to the disposal galleries et al. in the future. Appendix as CD-ROM. (J.P.N.)