Development of a particulate permeation grout consisting of ft y ash and acid mine drainage (AMD) treatment sludge was investigated. Results indicated that a mix consisting of 50 percent AMD sludge solids and 50 percent fly ash had the best characteristics with regard to flow reduction and pozzolan content. The measured hydraulic conductivity of the grout increased with increasing fly ash content and was on the order of 2 X 10-5 to 7 x 105 cm/sec. Effluent analysis indicated total alkalinity values, measured as CaC03, in the range of 12 to 97 mg/L. Total iron and manganese _were typically less than 1 mg/L for the remainder of the test period for all grout mix ratios. The aluminum concentration ranged from 1 to 1.8 mg/Land began to rise slowly as the testing proceeded. The highest value reached was between 3.6 and 4.0. The increases in aluminum concentrations closely followed the noted increases in alkalinity and pH. Results from bench scale testing indicated that grouting provided one to two orders of magnitude reduction in the hydraulic conductivity. This reduction was achieved by grouting 59 to 64 percent of the voids. Effluent analysis from the bench scale testing indicated a pH of 8.6 to 8.9 and iron, manganese, and aluminum of less than 1 mg/L for all samples collected during the testing period of approximately 2 months.

Currently, only 20 to 25 percent of approximately 50 million tons of fly ash generated each year is used (1). The remainder is disposed of mainly in landfills and slurry ponds (2). At the same time, the disposal of sludge generated from the treatment of the acid mine drainage (AMD) generated from the coalfields of the eastern and midwestern United States presents another waste management challenge. The treatment of mine water entails the addition of chemical agents, which produces large quantities of chemical floe in the form of sludge. Common chemicals added include calcium hydroxide, calcium oxide, sodium hydroxide, sodium carbonate, and ammonia (3, 4). On-site treatment of AMD with calcium oxide produces an abundant supply of sludge with potentially desirable characteristics. The sludge contains some fraction of unreacted lime, which can act as a catalyst to enhance the pozzolonic reactions in fly ash material. The need to develop new uses for fly ash and to dispose of the AMD sludge provides a strong impetus to investigate the use of both, in combination, to develop economical and effective grouts for highway applications where mass use is possible. A mix of fly ash and AMD sludge can be used to develop particulate permeation grouts for filling interstitial voids and fissures in rock or soil. In highway applications, permeation grouting is commonly used to control seepage in granular soils and fractured rock, control seepage in excavations, increase the bearing capacity of granular soils and shattered rock, improve slope stability, and strengthen brick and masonry structures (5).·