Textural Alterations in Coal Fly Ash due to Alkali Activation

Over the years, coal fly ash has been used as a backfill material in embankments, mines, roads and around pipelines. Recently, there has been a growing interest in its alkali activation for synthesis of both geopolymers and highly porous minerals known as zeolites. These end products find applications as cement admixtures, molecular sieves, and for contaminant depuration in aqueous media. In this regard, the textural characteristics, viz, particle size, pore size, and pore structure distribution characteristics of alkali activated fly ashes elucidate their potential as porous additives to cement and concrete, reactive media in permeable reactive barriers, and sorbents for contaminant removal. With this in view, this study investigates the particle size and pore structure modifications occurring in calcium hydroxide-based activation of coal fly ash. Furthermore, the morphological features also show the effect of alkali interaction on the reduction in larger sized particles and on the steady growth in smaller-sized crystals. (C) 2016 American Society of Civil Engineers.