Mechanical transformation of phyllite mineralogy toward its use as alkali-activated binder precursor

Abstract

The mechanical activation of phyllite for use as an alkali-activated material was studied. Prolonged milling of phyllite resulted in reduced particle size and a structural reorganization of the material, leading to incremental increases in amorphous content, which further resulted in the improved reactivity of phyllite in an alkaline environment. Quantitative X-ray diffraction results showed that the phyllite consisted of quartz, muscovite, chamosite, albite, and X-ray amorphous phases. Among the crystalline phases, muscovite and chamosite underwent the most structural reorganization, leading to a more disordered structure due to prolonged and intensive milling. The structural reorganization was also established through Fourier-transform infrared spectroscopy. Dissolution tests in 6 M NaOH showed incremental increases in leached Al and Si elements with increased milling time. After geopolymerization of mechanically activated phyllite, calorimetric studies showed exothermic reactions, and a 28-day compressive strength of 25 MPa was achieved for paste samples cured at room temperature. This study ascertained the potential utilization of phyllite mineral waste in sustainable cement applications.