Portland Cement: Hydraulic Reactive Components, By-Product

  • Thread starter SherlockOhms
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In summary, the major hydraulic reactive components in Portland Cement are alite and belite, as stated in the Wikipedia article on alite. The undesirable by-product during the cement hydration reaction varies depending on the application, but one potential example is calcium hydroxide, which can affect the pH and potentially facilitate the leaching and migration of radionuclides in certain applications such as storing nuclear waste in cementitious waste forms. The strength and cohesion of cement is mainly due to calcium-silicate-hydrate (CSH).
  • #1
SherlockOhms
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Could someone tell me the major hydraulic reactive components in Portland Cement and also the undesirable by-product during the cement hydration reaction? Thanks.
 
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  • #2
I believe 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.
 
  • #3
Useful nucleus said:
I believe 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.

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?
 
  • #4
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).
 
  • #5
Is calcium hydroxide an undesirable product in the cement? I know that CSH is what gives it it's strength, right?
 
  • #6
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.
 
  • #7
Thanks for the help. Great stuff!
 

1. What is Portland Cement?

Portland Cement is a type of hydraulic cement that is made by heating a mixture of limestone, clay, and other minerals in a kiln at high temperatures. It is a key ingredient in concrete, mortar, and other construction materials.

2. What are the hydraulic reactive components in Portland Cement?

The hydraulic reactive components in Portland Cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. These compounds react with water to form a strong, durable binder that holds the cement and aggregates together.

3. What are the by-products of Portland Cement production?

The by-products of Portland Cement production include carbon dioxide, which is released during the heating process, and various particulate matter such as fly ash and silica fume. These by-products can be used in the production of other materials or disposed of in an environmentally responsible manner.

4. How does Portland Cement differ from other types of cement?

Portland Cement differs from other types of cement, such as lime or gypsum cement, in its composition and production process. It contains specific proportions of the hydraulic reactive components mentioned earlier, and is produced in a kiln at much higher temperatures than other types of cement.

5. What are the main properties of Portland Cement?

The main properties of Portland Cement include high compressive strength, low shrinkage, and good durability. It also has a relatively fast setting time, making it suitable for a wide range of construction applications. However, it is important to use it properly and in the correct mixture to achieve the desired results.

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