Valorization of construction and demolition (C&D) and industrial wastes through alkali activation

In the present experimental study, the valorization of construction and demolition (C&D) and industrial wastes, namely ferronickel slag and red mud, through alkali activation is investigated. Specimens were produced by mixing various proportions of the raw materials with NaOH and sodium silicate solutions. The paste was cast in cubic metal moulds with an edge of 5 cm, cured at 80 °C for 24 h and then aged for 7 days at room temperature. The produced specimens were subjected to compressive strength testing. The effect of the molarity of the activating solution, the mineralogy of the raw materials and the ratios of SiO2/Al2O3 and SiO2/(Al2O3 + CaO) on the compressive strength of the final products was investigated. Also, the effect of high temperature heating (400-800 °C) on the structural integrity of the produced specimens was assessed. The use of analytical techniques, namely X-ray diffraction, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy provided insights on the morphology, structure and thermal resistance of the produced specimens.