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Title: The Influence of the Different Factors on the Stability of the AFt and AFm Phases

Author(s): Svetlana Samchenko and Evgeny Makarov

Publication: Symposium Paper

Volume: 326


Appears on pages(s): 83.1-83.10

Keywords: AFt and AFm phases, decomposition, crystallization, structure formation

DOI: 10.14359/51711066

Date: 8/10/2018


The crystallization of the AFt and AFm phases plays an important role in the structural formation and hydration of cement stone. Presently, significant attention is paid to the stability of the AFt and AFm phases in the different conditions; and, to the properties of its reconstruction due to impacts from temperature and reductions in moisture. This paper describes the stability of the AFt and AFm phases in these different conditions. The stability of the AFt and AFm phases has studied by their solubility in water and in aqueous solutions of sodium chloride and sodium sulfate at low and high temperatures. As a result, the AFt phases are least affected by water at high temperatures. The saturation of the liquid phase with ions proceeds very slowly. The extended state of the AFm phases in water leads to partial decomposition and crystallization of the ettringite. The AFt phase solubility increases with an increase of temperature and concentration of NaCl solution. In conditions of prolonged exposure to solutions with concentrations of 1 and 5% of NaCl and at temperatures of 20°C [68 °F] and 50°C [122 °F], a small amount of Friedel salt is formed. In conditions of exposure to a solution of Na2SO4 the AFt phases are in equilibrium with the sulfate medium and the dissolution of its crystals does not occur at any temperature.