Portland Cement.

  1. Could someone tell me the major hydraulic reactive components in Portland Cement and also the undesirable by-product during the cement hydration reaction? Thanks.
  2. jcsd
  3. I belive alite (and to some extent belite) are the majot reacive phases in portland cement.
    See: http://en.wikipedia.org/wiki/Alite

    Regarding the other question, "undesirable" in what sense? For every application there is a corresponding undesirable byproduct.
  4. Thanks for that. To be honest, I'm not sure. I was just reading a past exam question and it stumped me. I have a feeling it may be Sodium Hydroxide because I think I remember our lecture mentioning that before. Does that sound correct?
  5. Sodium compounds do not play a role in portland cement. Calcium and Silicon dominate the scene in cement. Before mixing with water, the klinker is mainly alite and belite. After mixing with water, the cement paste is dominated by calcium-silicate-hydrate and Ca(OH)2 (portlandite).
  6. Is calcium hydroxide an undesirable product in the cement? I know that CSH is what gives it it's strength, right?
  7. I cannot give a general statement about Ca(OH)2 in all applications. But one application I'm familiar with is storing nuclear waste in cementitious waste forms for ultimate disposal in geological repositories. In such application it is highly undesirable to have Ca(OH)2 because its presence elevates the pH in the system and so can facilitate the leaching and migration of radionuclides.

    And you are right cement cohesion and strength is mainly due to C-S-H.
  8. Thanks for the help. Great stuff!
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