MICROTOPOGRAPHY OF HIGH-CALCIUM FLY-ASH PARTICLE SURFACES

Tapping mode atomic force microscopy (TM-AFM) has been used to image t he surfaces of glassy spheres from high-calcium fly ash (HCFA). TM-AFM provides high-resolution images of such spheres under ambient conditi ons (e.g no vacuum and no conductive coating), showing topographic det ails which were not accessible with conventional electron microscopy. Combined single-particle X ray diffraction and TM-AFM allows identific ation of nanometre-sized anorthite, gehlenite, anhydrite and magnetite crystals attached to the glassy spheres. Furthermore, the TM-AFM tech nique revealed that the glassy matrix is quite inhomogeneous even on t he lower nanometre scale. The spatial distribution of reactive and ine rt mineral phases attached to fly ash particle surfaces provides infor mation about their high-temperature formation, which may be relevant t o their subsequent reactivity during hydration.