Image analysis: a tool for the characterisation of hydration of cement in concrete ¯ metrological aspects of magnification on measurement

This study aims at seeking what magnification is optimal in view to evaluate the hydration state of cement-based materials. When observing surfaces of flat polished sections of cement paste and mortar under SEM in BSEI mode at 100×, 200×, 400×, 600×, 1000× magnifications, an image analysis procedure, derived from the entropy maximisation, is applied to evaluate the area fraction of the anhydrous remnant cement grains AA (NH) at a given maturity