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Title: Performance assessment of stabilised/solidified waste-forms
Author: Antemir, Aurora
ISNI:       0000 0004 2688 7543
Awarding Body: University of Greenwich
Current Institution: University of Greenwich
Date of Award: 2010
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A method to treat contaminated land is stabilisation/solidification (S/S), which physically encapsulates and chemically stabilises the contaminants. The current knowledge on the behaviour of S/S systems is based upon scarce and incomplete data, mostly obtained from laboratory simulations or small scale trials of the technology. The field performance of S/S soils is largely unknown. The aim of this research was to improve the understanding of the long-term performance of S/S soils, by examining samples retrieved from eight full-scale remedial operations. The sites were selected to encompass a broad range of contaminants, binder systems, environmental exposures, and ages since the remediation. Conceptual models for each site were developed, based upon historical information from the literature. The models were used to identify the environmental loads, acting at the sites, and to predict their likely impact on the S/S soils. These impacts were considered by examining the microstructure, mineralogy, leaching behaviours and mechanical properties of the aged soils. Risk indicators for the performance of S/S soils were identified and they included reactions involving sulfates, carbonation, microcracking and the presence of weathered minerals. There was no link between the age of the S/S soils and degradation. The performance of the S/S soils was site specific and was influenced by the design of the remediation formulation, the implementation of the treatment and not least the environment of exposure. The behaviour of S/S soils is commonly compared to that of concrete. However, whilst the results suggested that some degradation mechanisms occur, properties such as permeability and unconfined compressive strength differed. The S/S soils were two orders of magnitude weaker and five orders of magnitude more permeable than normal concretes. Microstructural investigations revealed that although expansive phases developed with time in the SIS soils, there was no damage associated with them. According to their mechanical properties seven out of eight soils performed to their design criteria, up to 16 years after remediation. However, three sites failed to meet the limits following pass/fail leaching tests. This was due in part to the choice of leaching test carried out for the evaluation and the use of inappropriate remedial leaching limits, such as Drinking Water Quality values. However, the pH dependent leaching test showed that the contaminants were well immobilised in the old SIS soils and their release, at the natural pH of these soils did not exceed 1 mg/1. The acid resistance of the aged SIS soil was low to moderate and was mainly assured by the carbonates present. This fact will impact on the durability of SIS soils; however, estimates from the literature indicate that the acid resistance of carbonated materials would be exhausted in thousands of years. Based upon these results, the integrity of the soils had endured, and no obvious signs of impending failure were observed.
Supervisor: Hills, Colin ; Carey, Paula Sponsor: SITA Environmental Fund ; Portland Cement Association ; French Environment and Energy Management Agency (ADEME) ; Environmental Geotechnics Ltd ; Welsh Assembly Government ; Environment Agency (England and Wales) ; United States Environmental Protection Agency (USEPA) ; Contaminated Land: Applications in Real Environments (CL:AIRE ) ; Celtic Technologies Ltd ; English Partnerships
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TD Environmental technology. Sanitary engineering