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EnglishCemented clays are regularly employed as cut-off walls to isolate polluted soils or in ground improvement technologies. The objective of this research was to evaluate the performance of a polymer-treated bentonite (HYPER clay) and its impact on hydraulic and mechanical properties of cement-bentonite (CB) mixtures in contact with sulfates. In this research, bender elements were installed in a hydraulic conductivity cell, to simultaneously monitor the small-strain shear modulus (G(0)) and the hydraulic conductivity (k) of cement-bentonite mixtures. Initially, during permeation with deionized water, an increase of G0 with time was observed, due to cement hydration (hardening). Conversely, after prolonged permeation with sulfates, a decrease of G0 and a gradual increase of k are expected due to degradation of the cemented material. Preliminary results show that k of mixtures containing untreated bentonite increases due to contact with sulfates; conversely, k of mixtures containing HYPER clay remains unaffected. The stiffness modulus G0 was not significantly affected after a sulfate contact period of about 100 days in none of the cement-bentonite mixtures. More extensive monitoring is required for evaluating long-term mechanical degradation. These observations suggest that the use of polymer-treated bentonites could improve the resistance of cement-bentonite mixtures to sulfate attack maintaining a low hydraulic conductivity.
| Titolo: | Hydraulic and mechanical behaviour of cement-bentonite mixtures containing HYPER clay: impact of sulfate attack |
| Autori: | |
| Data di pubblicazione: | 2015 |
| Abstract: | Cemented clays are regularly employed as cut-off walls to isolate polluted soils or in ground improvement technologies. The objective of this research was to evaluate the performance of a polymer-treated bentonite (HYPER clay) and its impact on hydraulic and mechanical properties of cement-bentonite (CB) mixtures in contact with sulfates. In this research, bender elements were installed in a hydraulic conductivity cell, to simultaneously monitor the small-strain shear modulus (G(0)) and the hydraulic conductivity (k) of cement-bentonite mixtures. Initially, during permeation with deionized water, an increase of G0 with time was observed, due to cement hydration (hardening). Conversely, after prolonged permeation with sulfates, a decrease of G0 and a gradual increase of k are expected due to degradation of the cemented material. Preliminary results show that k of mixtures containing untreated bentonite increases due to contact with sulfates; conversely, k of mixtures containing HYPER clay remains unaffected. The stiffness modulus G0 was not significantly affected after a sulfate contact period of about 100 days in none of the cement-bentonite mixtures. More extensive monitoring is required for evaluating long-term mechanical degradation. These observations suggest that the use of polymer-treated bentonites could improve the resistance of cement-bentonite mixtures to sulfate attack maintaining a low hydraulic conductivity. |
| Handle: | http://hdl.handle.net/11566/282982 |
| Appare nelle tipologie: | 4.1 Contributo in Atti di convegno |
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