Tome Architecture and management of a geological repository - Andra

5 – B waste repository zonelinked to granulate size and dimension and shape of the fibres. A self-placing concrete was thereforesought, which does not need vibration to position it.Two types of formulations were developed:- an initial formulation basis was defined using CEM I with the addition of 10% silica fume on theone hand and limestone filler or fly ash on the other, for a total mass of cementitious materialclose to 500 kg/m 3 and between 170 and 200 kg/m 3 of water. The W/C ratio obtained is less than0.35. Granulates and sands are Boulonnais limestone for a total mass of around 1700 kg/m 3 . Thefibres are stainless steel hooked fibres for 30 kg/m 3 (or 56 kg/m 3 for the variant withoutreinforcement).- a second formulation basis was defined using CEM V with the addition of 5% silica fume for atotal mass of cementitious material close to 500 kg/m 3 and a mass of water between 170 kg/m 3 .The W/C ratio obtained is less than 0.35. The fibres are stainless steel straight fibres for 85 kg/m 3 .Furthermore, the specific formulation for the lid of the standard package (hydrogen porosity) wasdeveloped on the basis of CEM I with limestone filler but no silica fume and only 25 kg of stainlesssteel hooked fibres.The formulations developed and used to produce demonstration models allowed to reach the fixedobjectives.5.3.3.7 Evolution of pH in a repository situationThe choice of materials and development of the formulations presented above means that a target pHfor fresh concrete can be set at 13, which will rapidly fall to around 12.5 once the concrete hasmatured. Then, depending on the evolution of the concrete and its chemical breakdown, particularlyby hydrolysis, the pH will fall very slowly to a pH of about 10.5 in degraded state [41].5.3.4 Manufacturing techniquesThis section presents the envisaged manufacturing techniques [40].In 2004 and 2005 joint work by Andra and CEA resulted in manufacturing full-scale containerdemonstrators: two variants of the standard package for B2.1 primary packages (fibred and reinforcedbody, and fibred plain body) and a variant with improved retention capacity for B5.2 primarypackages.A program for assessing the performance of the manufactured objects has also been set up, particularlyfor early characterisation, the study of the containers-lids coupling (concreting joints and cast lid) anddropping resistance.5.3.4.1 Manufacture of standard prefabricated disposal packagesThe principle for manufacturing standard packages consists of maximising the number of stagesinvolved in a non-irradiating context, so that manufacturing quality can be checked as simply aspossible and manufacturing costs optimised.Two types of element are factory-manufactured in a non-irradiating environment: bodies and lids. Thelast operations, final primary package emplacement and disposal package closure, are carried out inirradiating cells.The bodies and lids are prefabricated in steel moulds (cf. Figure 5.3.3).Dossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY126/228