Pricing of raw materials - lime, cement, petcoke and aluminium powder also at this time in favor of AAC blocks when compared to clay bricks. Fly ash is one of the vital raw components for AAC blocks. In India, many thermal electricity plants produce loads of coal waste (fly ash); https://aacbricksplant60245.tribunablog.com/the-basic-principles-of-aac-bricks-plant-42280149