A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
New perspectives for geosynthetic clay liners using calcium bentonite
Recent investigations of excavated GCLs have shown that sodium (Na) bentonite undergoes an ion exchange by calcium (Ca) ions, converting it partially or fully into a calcium bentonite. As a result the original bentonite properties change, as well as the GCL permeability. It increases extremely when the converted bentonite layer dessicates getting irreversible cracks. Ca-ions causing ion exchange are usually present in most soils in situ. Initial employment of Ca-bentonite in a GCL eliminates the effect of ions exchenge right from the outset. Since 1997 after extended research and testing the utilisation of a sewn GCL containing approximately 10000 g/m2 Ca-bentonite has been started. In lab trials with Ca-enriched water the new GCL performed much better compared to the sodium GCL tested. Based on the lower water adsorption of a Ca-bentonite the moisture content in saturated state is much lower than that of a Na-bentonite and the corresponding plasticity index, too. In conclusion, the Ca-GCL needs less moisture and is less sensitive to water reductions in site compared with a Na-GCL. The range of shrinking is limited by the low swelling capacity too. The high bentonite content necessary to achieve a low permittivity makes the new GCL more resistant to mechanical and chemical effects.
New perspectives for geosynthetic clay liners using calcium bentonite
Recent investigations of excavated GCLs have shown that sodium (Na) bentonite undergoes an ion exchange by calcium (Ca) ions, converting it partially or fully into a calcium bentonite. As a result the original bentonite properties change, as well as the GCL permeability. It increases extremely when the converted bentonite layer dessicates getting irreversible cracks. Ca-ions causing ion exchange are usually present in most soils in situ. Initial employment of Ca-bentonite in a GCL eliminates the effect of ions exchenge right from the outset. Since 1997 after extended research and testing the utilisation of a sewn GCL containing approximately 10000 g/m2 Ca-bentonite has been started. In lab trials with Ca-enriched water the new GCL performed much better compared to the sodium GCL tested. Based on the lower water adsorption of a Ca-bentonite the moisture content in saturated state is much lower than that of a Na-bentonite and the corresponding plasticity index, too. In conclusion, the Ca-GCL needs less moisture and is less sensitive to water reductions in site compared with a Na-GCL. The range of shrinking is limited by the low swelling capacity too. The high bentonite content necessary to achieve a low permittivity makes the new GCL more resistant to mechanical and chemical effects.
New perspectives for geosynthetic clay liners using calcium bentonite
Neue Perspektiven für geosynthetische Ton-Auskleidungen unter Verwendung von Bentonit
Alexiew, N. (author)
2000
6 Seiten, 4 Bilder, 1 Tabelle, 15 Quellen
Conference paper
English
NEW PERSPECTIVES FOR GEOSYNTHETIC CLAY LINERS USING CALCIUM BENTONITE
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