High-volume, high-value usage of Flue Gas Desulfurization (FGD) by-products in underground mines Phase 1: Laboratory investigations. Quarterly report, July 1994--September 1994

During the quarter a second series of samples were collected and partially characterized chemically and mineralogically. The samples were collected at the disposal site operated by Freeman United Coal Co. The second collection was necessary because of deterioration due to hydration of the original samples. A study of the hydration characteristics was completed during the quarter. Important reactions included the immediate formation of ettringite and portlandite. The hydration and transformation was found to be a slow process. A second phase of gypsum formation from ettringite deterioration was identified. The slow hydration of anhydrite with its resultant swell is a potential problem which will be addressed further. Geotechnical characterization, during the quarter included completion of the preliminary characterization, analysis of the findings, experimentation with sample preparation for the final characterization/mix design, and design of the final experimental program. The analysis of the coals collected during the core drilling and hydrologic planning were completed. Also during the quarter a meeting was held with representatives of the shotcrete industry to discuss transport systems for emplacement. The pros and cons of pneumatic and hydraulic systems were discussed and plans formulated for further investigations