LAUSR

Abstract Twelve selected aggregates sintered from granite-marble-sepiolite wastes containing different proportions of powdered carbon fiber (FC) and thermoplastic (P) were studied by Rietveld X-ray diffraction, microscopy and thermal techniques to assess the influence of heating temperature (1100, 1125 or 1150 °C), dwell time (4, 8 or 16 min) and additive on mineralogical and textural features. Only small proportions of quartz, plagioclase and alkali feldspar withstood the sintering process from the original mineralogy, while glass increased from 36% to 70% as temperature and dwell time were risen. Some augite (6.5%) was neo-formed at about 980–1025 °C, far below the sintering temperatures. The addition of P barely affected the mineralogy, while FC promoted glass-evolution and the development of a highly porous fiber-microsphere-holding texture in which the phenocrysts observed in other specimens were almost absent. Glass-formation was connected with lower solid-phase density, less water absorption and greater closed porosity in the aggregates.