Development of magnesium-silicate-hydrate mortars using magnesium hydroxide for Magnox waste encapsulation

A novel approach to reduce the volume of the UK legacy Magnox waste is to use the Mg(OH) 2 -rich sludge as a component in a magnesium-silicate-hydrate (M-S-H) mortar. This study looks at the potential to incorporate a simulant corroded magnesium sludge (CMgS) into a mortar that achieves the encapsulation criterion. The optimum M-S-H mortar has a binder molar ratio of 0.5, resulting in 46.6 wt% of the mortar being CMgS sludge. This mortar had compressive strengths of 25 MPa at 60 days with a connected porosity of 6.5 % at 6 months, and this meets the requirements for a waste encapsulated grout. The work demonstrates the potential to use a Mg(OH) 2 -rich sludge, obtained from Magnox Swarf Storage Silos as a raw material in M-S-H mortars in waste encapsulation, with associated cost and space savings.