Performance assessment of stabilised/solidified waste-forms

Antemir, Aurora (2010) Performance assessment of stabilised/solidified waste-forms. PhD thesis, University of Greenwich.

Abstract

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.

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