Stabilization/solidification of sludges containing heavy metals by using cement and waste pozzolans

The experiments were carried out with 16 mixtures of cement, fly ash slag, and shell-lime; each of these mixtures was blended with water. The research also evaluated an optimal S/S process designed to encapsulate inorganic ha zardous wastes (heavy metals) within cement, pozzolanic materials, and the accelerators which are Na2S, NH4Cl, FeSO4, and water glass, thereby creatin g a non-hazardous product. Characteristics of the stabilized/solidified pro duct, including compressive strength and metal concentration in the leachat e, were evaluated. The compressive strength of 146 kg/cm(2) is attainable f or solidification additives alone cured at 23 degrees C for 28 days. Optima l mixtures are those which contain 14 % of slag, 55 % of fly ash, 14 % of s hell-lime, and 17 % of cement. The optimal mixtures with the accelerator fo rmulations are effective in solidifying electroplating and tanning waste sl udges, alone with respect to reducing leachability. Consequently, the formu lations are effective both with respect to the achievement of acceptable co mpressive strength and the reducing leachability after the increase of ceme nt and the decrease of water-cement ratio. Appropriately blended mixture of the pozzolanic materials can serve as binding agents for solidifying waste s.