Crystal Chemistry of Cement-Clinker Minerals and Melt Differentiation Reaction of Interstitial Melt

Microtextures of belite induced by polymorphic phase transitions and a remelting reaction have been reviewed, together with the melt differentiation reaction of interstitial melt. In the α-to-α'H phase transition, the α'H-phase nucleates as lamellae within the parent α-phase so as to realize a good lattice matching across the interface. The remelting reaction, in which the α-phase belite decomposes into a liquid and the α'H-phase during cooling, is necessarily preceded by the α-to-α'H phase transition. The lamella boundaries provide heterogeneous nucleation sites for the exsolving liquid. A variety of microtextures results depending on the surface tension between belite lamellae and exsolved liquid as well as on the cooling rate. As the simultaneous crystallization of zoned ferrite and belite proceeds during the cooling process of clinkers, the coexisting melt progressively increases the Al2O3/Fe2O3 ratio. After the termination of the ferrite crystallization, the aluminete and belite crystallize out of the differentiated melt.