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PROJECT RESULTS / Annual Technical Results

Year 5 : ESDRED TECHNICAL RESULTS to January 2009

• Presentation
• Module 1
• Module 2
• Module 3
• Module 4

Module 4: Low pH shotcrete for rock support and plug construction technology

Summary :

The work consisted first of designing low-pH cement formulations and then of preparing several concrete designs suitable for the construction of sealing plugs and for rock support. In both cases shotcreting was used as the construction method. Afterwards tests were conducted to demonstrate the feasibility of using low-pH shotcrete for rock support and plugs.

For the ENRESA part (sub-module low-pH shotcrete plug). The selection of cement, cement formulations and concrete design were done CSIC-IETcc in Madrid. Shotcreting trials were managed by AITEMIN in León (Spain), Äspö (Sweden) and Hagerbach (Switzerland). Then a short plug and a long plug were subsequently constructed in 2 different URL's. The short plug was loaded to failure, (i.e. slippage), very quickly and monitored during the entire process (February 2006, Äspö URL). The full-scale longer plug, constructed in Grimsel URL, is still (January 2009) being loaded using the swelling pressure created by bentonite blocks which are being artificially hydrated. This is a much slower loading process more closely related to what would happen in reality (albeit still on a much faster time scale).

For the SKB – POSIVA – NAGRA part (sub-module rock support). The development of a low-pH shotcrete formula for rock support for conditions in Sweden started in September 2005. The formula developed in the CBI laboratory in Stockholm was then subjected to pilot tests in February 2006 and field tests at the Äspö HRL in April 2006. The NAGRA work for adaptation of the formula for conditions in Switzerland started after the vacation period 2006 and was finished with fields tests at the Hagerbach test facility in Switzerland in November 2006.

Work completed during the reporting period:

The Module 4 participants (AITEMIN, CSIC-IETcc, ENRESA, NAGRA, POSIVA and SKB) produced an integrated final report summarizing the work carried out in both sub-modules. It was a joint effort of all the participants, with the aid of ANDRA. The report content and responsibilities was outlined in August 2007 and all related activities ended on January 15th 2009.

Sub-module for low-pH shotcrete plug:

Once the water leakage through the long low pH plug was sealed by the bentonite buffer the operational phase restarted in November 2007. A new version of the test plan, considering an extension of the test period, was then issued in May 2008.

During the fifth year of the project the artificial hydration of the bentonite buffer progressed, water content and pressure increased, and test data were gathered and stored. At the end of December the sensors showed humidity values of 90 %, and total pressure values ranging between 1.4 and 1.8 MPa. The operational phase of the long plug test within ESDRED IP ended on December 31st, 2008 even though the monitoring of the demonstrator is still going on.

The information of the performance of the long-plug test, in the forthcoming years, will be followed through the MoDeRn project (7th Framework Programme EURATOM), in which most of the ESDRED members are involved.

The long plug test results were described in a deliverable report issued in February 2009.

Sub-module for rock support:

All the technical work was completed in Year 4.

The only rock support activity during the fifth year of the Project year has been report writing. The final technical report for Module 4 was issued on15 January 2009. Members of Module 4 have also provided input to the final report for the ESDRED Project. Elsewhere, SKB, Posiva and NAGRA have continued working in the field of low-pH cementitious material but outside the ESDRED Project.

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