Use of coal mining waste as pozzolanic material in new blended cement matrixes

Research and eco-innovation geared to obtain alternative sources of raw materials from waste constitute pathways for enhancing the competitiveness of resource-intensive industries. Cement and concrete manufacture calls for new sources of new, highly pozzolanic products to improve the mechanical properties and durability of the resulting matrices, while at the same time reducing production costs and environmental impact. Spanish coal mining wastes generated in the extraction and washing steps from a mine in the Castilla-León region were investigated. Mineralogically, these wastes are composed by kaolinite (20-30%), illite (45-70%) and quartz (5-15). This composition is very interesting in order to activate, by controlled thermal activation, the present kaolinite that generates metakaolin, a highly pozzolanic product. Morphological, textural and microstructural changes affect the activity and reactivity of activated wastes. These first studies open up a new research line, practically unknown to the international research community, and stand out the important economic and environmental benefits associated with the recycling of these wastes as supplementary cementing materials for future commercial blended cements.