The transformation process of clay minerals into pozzolanic products for use as active additives in cement matrixes has been closely studied by both the scientific community and the cement industry.Sourcing these additions from recycled waste products is widely prioritized in environmental policies, because of their associated environmental benefits.This paper reports, the scientific aspects related to the recycling of several inert wastes (coal mining, slate, waste from drinking water treatment plants and paper sludge) as an alternative source for the obtaining of future pozzolans, based on activated phyllosilicates.