Alkali-activation of calcined granitic waste: Reaction mechanisms and environmental implication for waste minimization

Waste management and the need for low-energy materials in the building sector are persistent challenges facing modern society. Hence, the valorization of natural, industrial or by-products waste through alkali-activation offers a reliable and sustainable solution. This paper seeks to address this challenge by examining the potential recycling of low-reactive completely decomposed granite (CDG), when applying calcination at 650 ? in an electric furnace for 2 h. In the experiment, kaolinite (Al2Si2O5(OH)(4)) was found to be the dominant mineralogical phase on the starting CDG. However, the presence of microcline (KAlSi3O8) and quartz (SiO2) minerals was predominant after calcination. Moreover, lower wavenumber band at around 985 cm(-1), linked to the stretching vibration of Si-O and Al-O groups was found in the calcined CDG, thus indicating a decrease in the long-range order of the crystalline phase as well as the formation of an amorphous structure. The dissolution of the predominant solid( 29)Si, Al-27 species showed that, calcined CDG exhibits high reactivity especially under strong NaOH concentration. Mechanical and physical properties analysis also proved the degree of compressibility and cohesiveness of the activated CDG mortars. In addition, findings from the embodied CO2 emission concluded that while CDG reactivity improvement and activation are somewhat energy intensive, the resulting products performance and their associated applications were found to be acceptable. From this point of view, this research suggested a reframing of the application of geopolymer technology in solid waste treatment, and encouraged the development of waste-derived activators.