SEM/EDX Characterization of the Hydration Products of Belite Cements from Class C Coal Fly Ash

Abstract

This paper presents the microscopic characterization of two types of fly ash belite cements and their hydration products by means of scanning electron microscopy, energy-dispersive X-ray microanalysis, and X-ray diffraction analysis. The cements were obtained from ASTM class C coal fly ash by the hydrothermal–calcination route in water (FABC-2-W) and NaOH 1Msolution (FABC-2-N). The hydration was studied during a period of 180 days at 211C and 495% RH. The results showed significant incorporation of aluminum (Al) into the C–S–H gel and other minor elements, with a presumable position close to that of aluminum-tobermorite. The C–S–H composition of the FABC-2-W is more stable over the hydration time than that of the FABC-2-N cement. Portlandite is scarcely formed during hydration.