High-calcium fly ash recovery from wet-stored condition and its properties

Abstract

Fly ash can undergo changes in its properties during the wet-stored conditions, leading to reactivity variability consequently affecting its potential applications. Evaluation of the material properties is considerably essential. This work reports on an investigation of changes in physical and chemical properties of high calcium fly ash after recovering from the wet-stored conditions. Herein the high calcium lignite fly ash with calcium oxide constituent in a range of 20%–30% is the focus of this study. Important characteristics of fly ash have been studied, including physical properties, morphologies, chemical composition, and crystallographic phase transformation. Relation of oxide composition including silica, alumina, ferric oxide, and sulfur trioxide, to wet-storing period has been established to visualize the effect of short-term storage in water on changes in the content of mineral bearing species in fly ash. The strength activity indices of the recovered fly ash samples cured for 7 and 28 days has been presented. The significant amount of free lime and soluble calcium, aluminum, and sulfur-bearing minerals varying with storage times are believed to play their pronounced role governing compressive strength.

Keywords

• fly ash
• high CaO
• recovery
• wet-stored
• strength activity index
• cement application