Reuse of mining waste as aggregates in fly ash-based geopolymers

Mineral production continues to be necessary for economic development, consequently also the management of mining and mineral-processing wastes represent a considerable issue in terms of recycling and economic strategies for the future. One of the most promising reuses for coarse-grained mining wastes, especially barren waste rocks from coal and metal mining, is their application in the building and construction sector. An experimental research has been developed with the aim of studying the possible reuse of waste rocks – coming from mining activities-as fine aggregates in a fly ash based geopolymer: physical, chemical and mechanical tests have been carried out in order to analyze in detail the interaction between the geopolymer binder and the rock waste aggregates. All the mixtures, characterized by an aggregate/binder/ratio ranging between 0.05 and 1, showed a final microstructure characterized by a rather homogeneous geopolymer matrix embedding the mining waste rock. The geopolymeric matrix governs the overall mechanical behavior of the system, thanks also to the strong interaction at the interface between matrix and aggregates (mining waste). Moreover, all the geocomposites satisfy the prescribed limit for inert or non-hazardous waste