[en] Although there are several types in low alkalinity cements, highly fly ash contained silicafume cement (HFSC) has been studied in JNC. It is demonstrated that pH of pore water of the cement indicates below 10.5 as results of other TRU study. However although chemical properties and basic mechanical behavior are well understood, workability so on in constructing is little investigated. Since the underground research laboratory plays a important role in investigating constructing technology, HFSC will be adopted for supporting rock cavern so on. It is required that workability of low alkalinity cements should be assessed. Major performance of workability in tunnel construction in rock will be investigated and R and D planning will be done toward the laboratory construction. Conclusion obtained in this study is described as followings. 1) As results of laboratory test, HFSC and LHHPC developed by AECL fulfil the requirements of shotcrete using by hardening accelerator with calcium-salpho-aluminate. It is concluded that HFSC and LHHPC can be applied for shotcrete. 2) The experiment upon corrosion of re-bars by facing saline water at a offshore is planned. 3) It is noted that pH decreases significantly with rise of silicafume content and that silicafume should be used as much as OPC. 4) It is investigated where the low alkalinity cement should be applied in a actual radio waste repository and R and D program in the laboratory is planned. (author)