HYDRAULIC CONDUCTIVITY AND LEACHATE CHARACTERISTICS OF STABILIZED FLY-ASH

Disposal of fly ash on land amounts to sacrificing precious land space . Recycling of fly ash is one of the methods of solving the disposal p roblem. Stabilization of a low lime fly ash with lime and gypsum was s tudied through large scale tests on the stabilized material designed t o simulate field recycling conditions as closely as possible, and foun d to be a very effective means to control hydraulic conductivity and l eachate characteristics. The effects of moulding water content, lime c ontent, gypsum content, curing period, and flow period on hydraulic co nductivity, and on leachate of metals flowing out of the stabilized fl y ash are reported herein. With proper proportioning of the mix, and a dequate curing, the values of hydraulic conductivity on the order of 1 0(-7) cm/s were achieved. The concentrations of As, Cd, Cr, Cu, Fe, Hg , Mg, Ni, Pb, and Zn in the effluent emanating from the hydraulic cond uctivity specimens of mixes with higher proportions of lime or lime an d gypsum were below threshold limits acceptable for contaminants flowi ng into ground water.