Durability of Mg-Si-hydrate-based cements from brucite

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Magnesium silicate hydrate cements are a new type of cement that exploits the strength generated when magnesium oxide is made to react with a soluble silica source to form a mostly amorphous hydrated gel of magnesium silicate (M-S-H gel). It is a perfect candidate for reducing the volume of waste from the fuel ponds in Sellafield as the solids in those ponds are mostly magnesium hydroxide, which can also be converted in M-S-H gel under the right circumstances, i.e. the waste would effectively be a large component of the binder in which it is immobilised. However, while hydrated magnesium silicate gels have been known for a long time as a by-product of magnesium sulphate attack on normal Portland cement, much less is known about its durability and long term behaviour. Therefore the project would explore (i) how sludges should be pre-treated to enable the production of a suitable wasteform as too much water will reduce the mechanical properties substantially and (ii) the durability, i.e. long term stability of such cements, to ascertain whether this new type of cement is likely to remain stable especially during the initial above ground storage of the waste.