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Estimation of Longevity of Portland Cement Grout Using Chemical Modeling Techniques

  • S. R. Alcorn (a1), W. E. Coons (a1) and M.A. Gardiner (a2)

Abstract

Portland cement has been identified as a likely candidate seal material by programs investigating the deep burial of nuclear waste as a disposal mechanism. The longevity of performance of cement grout is currently being investigated, along with bentonite, under the auspices of the Stripa Project. Coordinated laboratory, field, and modeling studies are underway to produce fundamental data, practical experience, and estimates of long-range performance, respectively. Long-term performance of cement grout is of particular concern. Since most of the solid phases of which grout is comprised are metastable, it is likely that grout performance will decrease with time. The question is whether performance will still be acceptable after this decrease. This issue is being addressed with the coupled use of geochemical and permeability modeling. For a simplified cement system, two mechanisms for chemical degradation have been considered: phase change and dissolution. For dissolution, both equilibrium (slow flow) and open (fast flow) systems have been analyzed as bounding scenarios. Granitic terrain groundwaters ranging from fresh to saline have been used in the analyses. To assess the consequences in terms of flow, an empirical relation between cement permeability and porosity has been developed. Performance changes with time have been predicted by making conservative estimates of local hydraulic head conditions for successive periods of repository history. For the granitic rock environments considered, preliminary results indicate that cement grout performance may be acceptable for tens of thousands to millions of years, providing its initial hydraulic conductivity is on the order of 10−12 m/s. Other conditions favoring long-term performance include minimizing the ettringite content of the grout, and emplacement at a site where the groundwater has an elevated TDS, and where the local hydraulic gradient is flat or repository resaturation times are short.

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[1] Alcorn, S. R.; Myers, J.; Gardiner, M. A.; and Givens, C. A., 1989, “Chemical Modeling of Cementitious Grout Materials Alteration in HLW Repositories,” in Waste Management '89, Tucson, Arizona, February 26-March 3, 1989, Arizona Board of Regents.
[2] Coons, W. E. and Alcorn, S. R., 1989, “Estimated Longevity of Performance of Portland Cement Grout Seal Materials,” Proceedings of the Joint NEA/CEC Workshop, May 22-25, 1989, Braunschweig, FRG.
[3] Bogue, R. H., 1955, The Chemistry of Portland Cement, Second Edition, Reinhold Publishing Corporation, New York, 793 pp.
[4] Deer, W. A.; Howie, R. A.; and Zussman, J., 1977, Introduction to the Rock-Forming Minerals, Longmans, London, 528 PP.
[5] Onofrei, M.; Gray, M.; Keil, D.; and Pusch, R., 1989, In Press, “Studies of Cement Grouts and Grouting Techniques for Sealing a Nuclear Fuel Waste Disposal Vault,” Material Research Society, Proceedings from 1988 Annual Meeting.
[6] Licastro, P. H.; Fernandez, J. A.; and Roy, D. M., 1989, “Mechanical Compatibility Between Selected Cementitious Material and Topopah Spring Member Tuff,” Sandia National Laboratories, SAND86-0558, 87 pp.
[71 Taylor, H. F. W., ed., 1964, The Chemistry of Cements, vol. 1, Academic Press, New York, 460 pp.
[8] Wolery, T. J., 1983, “EQ3NR, A Computer Program for Speciation-Solubility Calculations: User's Guide and Documentation,” Lawrence Livermore National Laboratory, UCRL-53414, 191 pp.
[9) Sarkar, A. K.; Barnes, M. W.; and Roy, D. M., 1982, “Longevity of Borehole an Shaft Sealing Materials: Thermodynamic Properties of Cements and Related Phases Applied to Repository Sealing,” Technical Report, Battelle Project Management Division, Office of Nuclear Waste Isolation, 52 pp.
[10] Atkinson, A.; Hearne, J. A.; and Knights, C. F., 1987, “Aqueous Chemistry and Thermodynamic Modelling of CaO-SiO2-H20 Gels,” United Kingdom Atomic Energy Authority, Harwell Laboratory, AERE R 12548, 21 pp.
[11] Onofrei, M. and Gray, M., 1989, “Cement Grout Longevity-Laboratory Studies, Interim Report to the Task Force on Sealing Materials and Techniques, Stripa Project, Ludvika, Sweden, March 1989,” Atomic Energy of Canada Ltd.
[121 Onofrei, M. and Gray, M., 1988, “Cement Grout Longevity-Laboratory Studies,” report to the Task Force on Sealing Materials and Techniques, Stripa Project, London, February, 1988, Atomic Energy of Canada Ltd.
[13] Gartner, E. M., and Jennings, H. M., 1987, “Thermodynamics of Calcium Silicate Hydrates and Their Solutions,” J. Am. Ceram. Soc., vol. 70, pp. 743–49.

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