Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687257
Title: Conversion of magnesium bearing radioactive wastes into cementitious binders
Author: Walling, Samuel
ISNI:       0000 0004 5922 9387
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Abstract:
The UK radioactive waste inventory contains sizeable portions of magnesium hydroxide rich Magnox sludges due to corrosion of historic wastes. These require disposal in suitable wasteforms, with one potential being solidification in a composite Portland cement matrix. This thesis investigates magnesium hydroxide as a key component in the production of a cementitious binder, attempting to maximise waste loading and improve wasteform integrity through integral usage of these wastes. Hydrated magnesium silicate cements were produced through reaction with amorphous silica, creating stable products comprising a poorly crystalline M-S-H gel. The formulations for this product were optimised, water contents reduced through the use of a polyphosphate dispersant, and the nature of the M-S-H binder investigated further. This was determined to be a lizardite-like structure, which is a stable mineral. This system was modified through the addition of sodium aluminate, resulting in formulations with varying ratios of silicon to aluminium, each of which produced various zeolitic phases along with a magnesium aluminium hydrotalcite phase. This addition improved the setting characteristics of the binders, but did not produce any additional magnesium silicates binders. Additionally to this, sodium carbonate activated slag cement binders blended with magnesium hydroxide were assessed. These were slower setting, low heat cements which formed stable mineral phases, largely unaffected by the addition of magnesium hydroxide. The chemistry of these binders was assessed over an 18 month period, remaining stable throughout. Ultimately it was proved that magnesium hydroxide can be utilised to form cementitious binders, but only in the absence of competing calcium based binding systems.
Supervisor: Provis, John ; Kinoshita, Hajime Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.687257  DOI: Not available
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