Explain AFM phase and AFT phase in Portland cement

What is AFM phase and AFT phase in Portland cement?

AFM Phase (Alite-Ferrite-Monosulfate Phase)

AFM Phase (Alite-Ferrite-Monosulfate Phase) is a compound formed during the early stages of cement hydration. It consists of three main mineral components:
  • Alite (C3S): Alite is the primary compound in Portland cement, accounting for the majority of its composition. It is responsible for providing strength to the cement paste.
  • Ferrite (C4AF): Ferrite is another primary compound in cement. It contributes to the overall strength and stability of the cement.
  • Monosulfate (C3A•CaSO4•12H2O): Monosulfate is a hydration product formed from the reaction of tricalcium aluminate (C3A) and calcium sulfate (CaSO4). It helps in controlling the setting time of the cement and provides some early strength.
The AFM phase plays a significant role in the initial hardening of cement and contributes to the early strength development. It also affects the setting time and influences the early hydration reactions.

AFT Phase (Alite-Ferrite-Trisulfate Phase)

AFT Phase (Alite-Ferrite-Trisulfate Phase) is a compound that forms during the later stages of cement hydration. It consists of the same mineral components as the AFM phase but with a different ratio:
  • Alite (C3S): Same as in the AFM phase.
  • Ferrite (C4AF): Same as in the AFM phase.
  • Trisulfate (C3A•CaSO4•3H2O): Trisulfate is another hydration product of tricalcium aluminate (C3A) and calcium sulfate (CaSO4). It forms later in the hydration process and contributes to the long-term strength development of the cement.
The AFT phase is associated with the development of long-term strength and durability of cement. It continues to form and transform over time, contributing to the ongoing hydration reactions and the overall performance of the cement.

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