Swelling characteristic of bentonite on pelletization and properties of fly ash aggregates

Earlier studies have established that aggregates could be produced from fly ash through pelletization, which has the advantages of reducing (1) environmental pollution and (2) consumption of depleting natural aggregates. Though cement, lime, and bentonite were used for improving the properties of fly ash aggregates, limited studies have been reported on the effect of binders on the pelletization process of fly ash. This paper discusses the relative performance of bentonite with two different swelling characteristics on the pelletization of fly ash. The variation of factors and its optimum level on the overall pelletization efficiency, efficiency of producing three individual size fractions, ten percent fines value, and water absorption were determined through a statistically designed experiment using response surface methodology. The maximum pelletization efficiency of fly ash aggregate was achieved with lower dosage level of high swelling bentonite. Higher factor levels facilitate enhanced ball growth, i.e., produce aggregate size fraction greater than 10 mm. Similarly, the maximum ten percent fines value and minimum water absorption result at the maximum level of the factors studied. The optimal level of factors for a given aggregate size fraction was almost similar, independent of swelling characteristics of bentonite, except for the variation in bentonite and moisture contents. © 2009 ASCE.