Applications of rejected fly ash in stabilization and solidification processes

Cement-based stabilization/solidification (S/S) systems with partial replacement of cement by pulverized fuel ash (PFA) have been widely used to minimize leaching of contaminants from hazardous wastes prior to land disposal. Traditionally, low-grade PFA (rFA) from the ash classifying process is largely rejected and unused due to its high carbon content and large particle size. This paper presents experimental results of a study on the applications of rFA in the cement-based S/S of a synthetic heavy metal waste. Results were compared to mixes containing the classified and finer ash (fFA). The compressive strength results show that cement-based waste forms with rFA replacement are suitable for disposal at landfill. The leaching test results indicate that rFA can be used in cement-based S/S wastes without compromising the performance of the S/S product and the long-term performance of cement-rFA waste form can be better than the cement-fFA waste form.