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Evaluation of a landfill cover construction based on secondary construction materials
2009 (English)Student paper otherStudent thesis
Abstract [en]

Large amounts of material will be needed to install covers on closed landfill constructions due to the application of EU landfill directive 1999/31/EC. Approximately 1 million t of ashes are produced in Sweden each year. The interest in substituting conventional construction materials for landfill covers by alternative materials increases by the possibility to implement advantages, such as saving natural resources and economic benefits, using SCM. But to use SCM advantageous for the intended purpose, additional problems compared to the use of conventional materials have to be solved, such as availability, storing, preparation, planning and the construction process itself. Thorough investigations and experiments to characterize the used materials are a necessity. At Tveta Landfill in Södertälje field investigations are performed concerning different cover construction designs. During an excavation in 2007 samples from the different layers of the cover of two test fields were collected. In this study the development of the cover constructions is investigated focusing the mechanical and chemical stability of the cover constructions. During the investigations the bulk density, WHC and total composition of the material were analyzed and a diffusion test was performed. No negative development of the mechanical properties of the material due to ageing processes could be determined. The results of the analyses show that the construction process itself influences the future mechanical and chemical conditions of the cover construction. For example, the delayed covering of the protection layer of area 1 by the vegetation layer resulted in displaced concentrations for most considered components within the solid matter. The comparison of solid matter content and leaching behaviour before installation and after excavation after two and four years, respectively, indicate a trend to decreasing concentrations for most of the concerned components. The trend is only weak due to the short time the material was in place and because the amount of water that percolated through the layers was reported to be small. For some components enrichment especially in the protection layer of area 4 was determined. It could be shown that this enrichment is caused by the superimposed vegetation layer material, which contains high concentration levels for some elements. The transport path of these components leading to a contamination of the other layers by leaching could also be disclosed. The leaching behaviour of the fly ash used in area 4 was studied in a diffusion test using leachate from the protection layer as a way to understand the influence of different layers on each other. Moreover, the comparison of the results from this test with another diffusion test using distilled water reveals different behaviour depending on the used leachant. The diffusion occurs in the initial phase of the experiment for the concerned diffusion controlled components influenced by the leachate of the protection layer. A difference in the leached amounts could also be noticed. The stabilization of the mineral liner due to the formation of clay minerals could not be proved analytically, but the precursors reported to be necessary for this process could be determined. Leaching was found to have the main impact on the stabilization of the cover construction, causing the reduction of component concentrations and the approach to an equilibrium state between the cover and its environment. It was shown that the influence of leaching emissions on the environment is controllable. A risk for the environment was determined by the contaminated vegetation layer of area 4, hence uncontrolled emissions of components into the environment by plants and animals may occur. As a result of this study it is shown that the implementation of SCM is possible. Whether constructing with SCM is successful or not strongly depends on anticipatory planning and the design, the knowledge of the materials properties, their development over time and their interactions.

Place, publisher, year, edition, pages
Keyword [en]
Technology, landfill cover construction, secondary construction, materials, waste management, fly ash, diffusion, leaching, mineral transformation, ageing
Keyword [sv]
URN: urn:nbn:se:ltu:diva-57203ISRN: LTU-PB-EX--09/071--SELocal ID: de3b8d93-a212-4e7c-a0f4-1844867d034cOAI: diva2:1030590
Subject / course
Project work, other
Educational program
Student paper other
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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