Melt differentiation and crystallization of clinker minerals in a CaO-SiO2-Al2O3-Fe2O3 pseudoquaternary system

In the CaO-SiO2-Al2O3-Fe2O3 pseudoquaternary system, the solid solutions of Ca3SiO5 [C3S(ss)], Ca2SiO4 [C2S(ss)], Ca-2(AlxFe1-x)(2)O-5 with 0.40 <= x <= 0.57 (ferrite) and Ca3Al2O6 [C(3)A(ss)] were crystallized out of a complete melt with 52.9 mass% CaO and Al2O3/Fe2O3 = 0.70. When the melt was cooled from 1673 K at 80 K/h, the crystals of ferrite with x = 0.40, C3S(ss) and C2S(ss) would start to nucleate from the melt at 1630 K. During further cooling, the x value of the precipitating ferrite would progressively increase and eventually approach 0.57 at 1613 K. The resulting ferrite crystals showed a zonal structure, the x value of which successively increased from the cores toward the rims. Actually, the x values of 0.43 and 0.52 were confirmed for, respectively, the cores and rims by EPMA. As the simultaneous crystallization of zoned ferrite, C3S(ss) and C2S(ss) proceeded, the coexisting melt would become progressively enriched in the Al2O3 component. After the termination of the ferrite crystallization, the C(3)A(ss), C3S(ss) and C2S(ss) crystallized out of the differentiated melt. The end result was the four phase mixture of ferrite, C(3)A(ss), C3S(ss) and C2S(ss), being free from the nucleation of Ca12Al14O33 solid solution. (C) 2009 Elsevier Ltd. All rights reserved.