The diffusion of reactants into the refractory substrate
and then the in situ corrosion reactions of the alkali oxide (K2O)
and alkali earth metal oxide (CaO) present in the atmosphere of
cement kiln preheater and cement raw meal with andalusite from
the refractory generated new K-aluminosilicate phases,i.e. kalsilite,
KAlSiO4 and leucite, KAlSi2O6, and Ca-aluminosilicate phase, i.e.
gehlenite, Ca2Al2SiO7. XRD diffractograms for each corroded zone
are depicted in Fig. 3