Leaching Characteristics of Lime-Treated Fly Ash

Fly ash has been used in many geotechnical applications, such as fill material in embankments and ash dyke raising. However, fly ash alone may not provide sufficient strength in every project, and its treatment is required. Fly ash has been treated with lime as it is a pozzolanic material. Fly ash, a waste material of coal burning might contain heavy metals such as lead (Pb) and chromium (Cr) as impurities. Leaching of such heavy metal ions in water results in the degradation of the quality of water. Adding lime to fly ash results in surface modification of fly ash particles. Hence, evaluating the leaching characteristics of lime-treated fly ash becomes necessary. In the present study, leaching characteristics of lime-treated fly ash were studied for lime content of 1, 2, 3, 4, and 5%. The shear strength of lime-treated fly ash was also evaluated by performing a series of unconfined compression (UC) tests. The toxicity characteristic leaching procedure (TCLP) were followed to obtain a leachate solution of lime-treated fly ash. The ICP-OES technique was used to determine the metal ion concentrations in the solutions prepared. It was observed that the concentration of Ca, Mg, and Cr ions increased in leachate with the addition of lime. The concentration of Pb and Zn decreased with the addition of lime.