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Title:
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Performance testing of a self-forming & self-repairing seal
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Author(s):
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Published by:
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Publication date:
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ECN
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1-8-2001
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ECN report number:
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Document type:
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ECN-C--01-082
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ECN publication
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Number of pages:
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Full text:
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17
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Download PDF
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Abstract:
A Self-Forming & Self-Repairing seal system (SF&&R) has been developed by the geotechnical research team from Dong-Ah Construction Industrial Co. Ltd. The system is to be applied as a top isolation for landfills. The seal system is based on the formation of a CaC03 and Ca0.Si02 precipitate in the pores on the interface of the two adjacent layers (top layer and bottom layer) of the SF&SR system. The SF&SR system consists of two layers placed upon each other, eachlayer has a specific composition. The reactive agents present in the top layer and bottom layer are transported to the interface of both layers to form a precipitate which in time will seal the pores on the interface. This will cause an increasing resistance to water percolation. A crack of the seal will result in restart of the precipitation reaction thereby demonstrating the self-repairing properties of the SF&SR system.
The permeability and permeability development with time of the SF&SR seal were measured using a permeability measurement instrument based on the falling head method. The starting permeability of the SF&SR system was low (1.5*l0-18 and 1.8*10-10 m/s) and transport of the reactants towards the precipitation zone was probably controlled by diffusion rather than by percolation processes due to this low permeability. This has also resulted in a somewhat slower formation of the SF&SR seal than in situations where the reactants were transported by
percolation.
After cracking the seal, the permeability increased to a value of approximately the starting permeability. In the period after cracking the seal the permeability was monitored again and it was clear that the system has self-repairing properties. The permeability decreased again with approximately the same speed as before cracking the seal.
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