Portland cement grout identified as BCT-1-FF (Bell Canyon Test 1-FF) was used in borehole plugging experiments in the Bell Canyon Tests in Hole AEC-7 at the Waste Isolation Pilot Plant site in New Mexico during September 1979 and February 1980. This grout was made with fresh water. A study of this grout was begun in August 1979 in the laboratory to evaluate the possible effects of temperature, pressure, and storage in fresh water or simulated groundwater (brine) on its phase composition and compressive strength at early ages. Phase composition was determined by X-ray diffraction. Temperatures ranged up to about 150 F and included elevation at a few hours age after mixing; pressure was as high as 1500 psi; specimens were stored in simulated groundwater (brine) or in fresh water. Data from 1 to 90 days showed: Higher temperature accelerated early strength gain. These differences essentially vanished by 90 days age. Hydration products as identified by X-ray diffraction were normal; this indicated that a temperature range of 78 to 153 F was not significant. Pressure did not affect composition. Storage in simulated groundwater (brine) or fresh water had no detectable effect. Since the BCT-1-FF grout mixture contained added sulfate, it formed more ettringite as judged by X-ray diffraction than comparable portland cement mixtures without added sulfate. (Author).

Some of the considerations involved in the development of hydraulic cement-based grout mixtures intended for use in the isolation of nuclear waste stored underground are longevity, impermeability, uniformity, ease of placement, and relevance to previously used systems. Work done at the Structures Laboratory of the U.S. Army Engineer Waterways Experiment Station on this subject has indicated that apparently adequate systems can be based on well known ingredients. Information on field testing and long-term testing of these grouts has confirmed this indication. The following conclusions are indicated: (a) Selection of control parameters such as flow time, time of setting, compressive strength, and permeability for a candidate grout mixture should be criteria used in the formulation of a grout mixture. (b) Once quantitative levels of such parameters have been established, the hydraulic cement-based grout system has adequate latitude in its formulation to accommodate these needs. (c) While longevity in nonaggressive environments and compatibility with host rocks is known in general for such systems, data for specific mixtures under specific conditions must be developed. A Standard Practice for Selecting Mixture Proportions for Hydraulic Cement-Based Materials Systems for Repository Sealing is presented as an Appendix. (Author).

Sealing of boreholes and underground excavations has not received much engineering attention until fairly recently. The growing awareness of and sensitivity to environmental concerns of the technical community as well as of the public at large has resulted in an increasing recognition of the fact that these geological penetrations may have an environmental impact. The issue of possible contamination resulting from migration along boreholes, adits, shafts or tunnels unquestionably has been raised most forcefully with in the context of nuclear waste disposal. Several nuclear waste disposal programs, notably the Civilian and the Defence programs of the US De partment of Energy, the US Nuclear Regulatory Commission and the Canadian and Swedish radioactive waste disposal programs have conducted major research efforts aimed at developing adequate seal designs for penet rations in host rock formations for high-level nuclear waste repositories. While a considerable data base has been gathered over the last two decades or so with regard to the performance of seals, most of the information is presented in research reports and widely scattered papers in journals and proceedings of conferences. Hence, the materials are not readily accessible to potential users such as designers, contractors or regulators who are not familiar with nuclear waste disposal programs.