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Title: Re-use and volume reduction of scabbled contaminated concrete arising from nuclear decommissioning
Author: Lord, Toby James Alasdair
ISNI:       0000 0004 7964 3876
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2018
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During decommissioning of nuclear sites, radioactively contaminated concrete is scabbled from the bulk, creating an intermediate level waste (ILW) stream, requiring encapsulation in a cementitious matrix prior to storage and eventual disposal. A co-disposal option was investigated, using the scabbled material as a cementitious replacement within encapsulation grouts, to immobilise other waste streams, removing the need for direct disposal and increasing the overall waste to container volume ratio. Encapsulation grouts have strict specifications on performance, and so the effect of the inclusion of scabblings on the grout was investigated. In this study, four simulant scabblings were synthesised, using a CEM I and CEM II based concrete, before they were crushed and ground, with half of the ground material from each undergoing accelerated carbonation, as the depth of scabbling is in the same range as the depth of carbonation in aged concrete. The scabblings were then used to replace predetermined percentages of the binder content in encapsulation grout mixes, with the cement to slag ratio (OPC:BFS) maintained at 1:3, and the effect on the hydration and engineering properties investigated. The scabblings were found to affect the hydration of the grout above that of solely the filler effect, with the presence of remaining anhydrous material, and calcium hydroxide for slag activation, affecting the overall hydration. Mixes with 10% inclusion showed similar overall hydration and engineering properties to a reference grout, while beyond 10% inclusion these properties were significantly affected. The carbonated scabblings were found to affect the hydration and engineering performance differently to the non-carbonated, with the presence of calcium carbonate creating a ternary blended cement, and the resultant improvement in engineering properties was found. Overall, it was found that replacement of the binder with up to 10% recycled scabblings is possible, with the grout properties remaining within the specification limits. Replacement levels above 10% are not feasible.
Supervisor: Black, Leon Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available