Dicalcium ferrite phase

Dibutylstibinic acid, 3 73 Dibutyltin diacetate, 24 823 Dibutyltin dilaurate, 24 823 Dicadmium triantimonide, 4 510 Dicalcium alumino monosilicate, phase in Portland cement clinker, 5 472t Dicalcium ferrite, phase in Portland cement clinker, 5 472t Dicalcium hexaborate pentahydrate,... 

As the magnetic properties of dicalcium ferrite Ca2Fe2C>5 are already known, it was considered interesting to investigate the magnetic behaviour of these solid solutions and to correlate it with the vacancy order-disorder transition. Thermomagnetic analyses were carried out to determine the Neel temperatures of these phases. 

In ordinary Portland clinker (corresponding to ASTM type I Portland cement) tricalcimn silicate is the most abundant phase, present in amormts between about 50% and 70%. Dicalcium silicate usually constitutes 15-30% of the clinker. Typical amounts of tricalcium aluminate are 5-10%, and of the ferrite phase 5-15%. In special Portland clinkers the individual clinker pliases may be present in increased or reduced amounts, or may be absent entirely. Free lime, free MgO and alkali sulfates are minor constituents of Portland clinker that are present only in small amounts or may be absent entirely. Calcium sulfate is only rarely a constituent of Portland clinker, but is intergroimd in limited amounts with it, to obtain Portland cement. In Table 2.1 different types of Portland cement are compared. 

High-iron clinkers contain well-developed acicular or prismatic crystals of the caldtrm alirminoferrite phase, as well as dicalcium ferrite. The A/F molar ratio in the alirminoferrite phase may be as low as 0.11 (Stark et ai, 1997b). 

Belite (or belitic) cements are produced by grinding belitic clinkers with limited amounts of calcium sulfate (gypsum or anhydrite). Such clinkers contain belite (dicalcium silicate) as their sole or main calcium silicate phase. In addition, they contain tricalcium aluminate and the ferritic phase. Alite (tricalcium silicate) may also be present in some belitic clinkers, but only in very limited amounts. They differ both from ordinary Portland clinker and from Portland clinker with an elevated C2S content (see section 2.4) by having a lower CaO content, which results in a lime saturation factor of not more than LSF=80. 

Alite-fluoroaluminate cement, also called regirlated set cement (in the USA) or jet-cemerrt (in Japan), contains tricalciirm silicate (50-75%) and calcitrm fluoroaluminate (20-30%) as its main corrstituents. Other corrstituertts may include the ferrite phase, dicalcium silicate, and free CaO. 

Abbattista, R, Burdese, A., Maja, M., High-Temperature Equilibria Involving Wustite, Iron, Calcium Oxide, and Dicalcium Ferrite Determination of Oxygen Pressure Using the Emf of Solid Electrolytic Cells (in Italian), Metall. Ital, 65, 675-678 (1973) (Phase Relations, Thermodyn., 16)... 

The corrosion process is seen in a field near the immediate hot face (Figure 20). Here dicalcium ferrite (bright phase) and dicalcium silicate penetrate around individual MgO crystals from aggregate particles. Several smaller rounded MgO crystals are in the final phase of dissolution. Even though dicalcium silicate is a compatible phase with MgO, it will still dissolve MgO—as... 

In the process formation two stages can be distinguish at the range of lower temperature to about 1300 °C, when the reactions proceed, as a rule, in the sohd state, in the presence of very low quantities of the liquid phase, and at higher temperature, at which it is already about 25 % of the melt. It is assumed that the dicalcium sihcate and calcium aluminate and ferrite are formed principally as the result of reactions in the sohd state. However, tricalcium silicate is formed by ciystalhzation from the liquid phase. 

Portland cement clinker is composed of fora principal phases alite, which is close to tricalcium orthosilicate Ca3[Si04]0, belite close to dicalcium orthosilicate Ca2[SiOJ, tricalcium aluminate Ca3[Al20g] and ferrite C2(A, F). Chemical composition of these phases is complicated by solid solutions, which have the decisive influence on their reactivity with water. For the elements from which chrrker phases are composed isomorphism is typical and very developed phenomenon. The highest concentration of isomorphic elements is encountered in tricalcium aluminate (about 12-13%), and then in alumino-ferrites (about 10-11%), belite (about 6%), and the lowest in alite (about 4 %). 

---