Phase equilibrium relations in a portion of the system Na-2-O-CaO-Al-2O-3-SiO-2

Abstract

A study of a portion of the system NazO-CaO-A\zOa-SiOz has been made as a step in the solution of the problem of the state of combination of NazO in portland cement clinker. Quenching data are given for compositions in the tetrahedron formed by 2CaO.Si02, CaO, NazO.AlzOa, and AIzOa, and phase diagrams are shown for three composition planes through the space model. Five invariant points were located approximately, at one of which 2CaO.SiOz, 3CaO.SiOz, 3CaO.AIz03, and NazO.8CaO.3AI20a are in equilibrium with liquid. This point, which is not a eutectic, occurs at 1,440° ± 10°C and has a composition of 3.5 percent NazO, 55.2 percent CaO, 31.0 p ercent AbOa, and 10.3 percent Si02• Evidence was obtained of the formation, under favorable conditions, of a solid solution between 3CaO.AI20 a and NazO.8CaO.3AI203 at temperatures below that of liquid formation. Present information indicates that N a20 may be present in clinker in several possible forms: (1) in glass, (2) as Na20.8CaO.3AIzOa or a solid solution of this compound and 3CaO.AIzOa, (3) in solid solution in 2CaO.Si02, (4) as inclusions of a soda-bearing phase in ,8-2 CaO.Si02 produced by ex-solution on inversion from a-2CaO.Si02.

Building research at the National Bureau of Standards

“…In 1917 Bates and Klein [240] prepared, in the pure form, tricalcium silicate, the most important constituent of Portland cement. This was followed by a systematic study of high temperature phase relationships of progressively more complex systems including the oxides of aluminum, iron, magnesium, sulphur, potassium and sodium [241][242][243][244][245][246]. The compounds found to be produced with pure materials at temperature equilibrium were characterized by optical and x-ray techniques, and compared with those observed in actual clinkers.…”

Phase-equilibrium relations of the common rock-forming oxides except water

“…above glass, a narrow field of devitrite was met, followed by a field of CaO-SiO2, The final mixture of this series had the composition 13 percent Na20, 10.0 percent CaO, 9.1 percent A12O3, 67.9 percent SiO2, liquidus 1156°C with CaO SiO2 as primary phase. Greene and Bogue (1946) studied two planes high in CaO. One was the plane CaO-2CaO SiO2and in it appear the compounds and 2Na2O -3CaO 5A12O3.…”