III. Hydration

Portland cement is essentially useless in powdered form and is only effective in binding objects together when it is mixed with water. Portland cement is a “hydraulic cement”, meaning it doesn’t harden until it is mixed with water. As stated earlier, Portland cement is made up of four major compounds. These compounds are often written in short hand form, the chart below shows the compounds formulas in shorthand form.

When the Portland cement is mixed with water the bonds of all the compounds dissolve and a large amount of heat is produced. Although the bonds break, the actually hardening doesn’t occur for many hours. This would allow people on planet Arda to transport the cement before it hardens. The Di-calcium silicate and the Tri-calcium silicate are responsible for the hardening and strength of the cement. The chemical reactions can be seen below:
Di-calcium silicates + water --->calcium silicate hydrate + lime
Ca₂SiO₅+ H₂O ---> CaO.2SiO₂ + CaC0₂
and
Tri-calcium silicate + water --->calcium silicate hydrate + lime
2Ca₃SiO₄ + 6H₂O ---> CaO.2SiO₂+ 3CaC0₂
Dicalcium silicates reacts with water very slowly, and therefore is not completely effective for up to a week. Tri-calcium silicate reacts with water much quicker, creating an initial strength in the cement, but is much less strong then product of the Di-calcium silicate with water. The other reactions that occur during hydration are very complex and are way to difficult for someone with a year of chemistry to understand.

It is apparent that although Portland cement may be to difficult to produce on planet Arda, the materials needed to do it will be readily accessible. After enough time on Arda, this much needed product can, and should be produced.

Sources

Images:

1.Limestone.5/19/03, .http://www.burrencollege.com/undergraduate-programmes/photos/limestone-beach_sm.jpg

Fuel Blending and Cement Kilns. 3/10/2002, http://www.enviornmental.usace.army.mil/library/pubs/tsdf/sec5-2/sec5-2.html

2.Pyrite. 5/18/03, http://www.fr.ch/mhn/images/mineraux/pyrite2.jpg

3.Gypsum.5/19/03, http://www.beavton.k12.or.us/greenway/leahy/00-01/rocks/gypsum.jpg

4.Cement Makin Process.5/18/03, http://www.landinst.com/infr/appls/images/a-c-map.jpg

5. Indide the Kiln.(5/17/05), http://gcisolutions.com/hcco10.gif

Books and Encyclopedias:

1. “Cement Making.”The World Book Encyclopedia. Ed. 8th ed. Vlo.3. Chicago: World Book inc, 1992.

2. True, Graham, Glassfibre Reinforced Cement Production and Uses (Scholium Intl. 1986).

3. Gladkov F., Cement (Imported Pub.1985).

Web Sites

1. Hydration of Portland Cement. 3/19/03, http://www.engr.psu.edu/ce/concrete_clinic/concmats/hydcem/hydration/hydration.htm

2.Concrete + Metal. 3/10/03,http://www.makersgallery.com/concrete/tech.html

3. Hydration Equations. 5/22/03, http://www.olemiss.edu/courses/engr313/engr314/materials.html

4. Cheny Lime and Cement Company. 3/28/03, http://www.cheyneylime.com/chemist.htm

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