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[[File:Portland cement Type1 of Taiwan Cement 20180501.jpg|thumb|Cement bags made in Taiwan.]]

'''Cement''' is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind [[sand]] and [[gravel]] (aggregate) together. Cement mixed with fine aggregate produces [[mortar]] for masonry, or with sand and gravel, produces [[concrete]]. Concrete is the most widely used material in existence and is behind only [[water]] as the planet's most-consumed resource.

Cement is primarily produced by slaking quicklime. This involves adding the quicklime to water to convert it from CaO to CaOH. In this state  it can be used as a pickling lime, as cement, plaster, mortar or as a food additive. Though there are many forms of cement, most involve taking limestone, aragonite or seashells, heating them above 900c to remove the organics, then slaking the resultant quicklime.

== Materials needed ==

* 80% '''Limestone (calcium carbonate)'''
* 15-20% '''[[Clay]] or Shale''' 
* 0-5% '''Rust powder ([[Iron|iron oxide]])'''
* '''Gypsum (CaSO₄)''' (5% of the total mass of previous mixture)
* A '''rotary [[kiln]]'''

== Crafting instructions ==

# Grind all ingredients into a fine powder using a mortar and pestle or ball mill. Mix thoroughly to get a uniform raw meal.
# Heat mixture in a crucible or kiln to 1450°C (2642°F) for about 30 minutes, forming pellets called clinker.
# Cool rapidly to preserve mineral phases (drop into dry sand or on a steel plate).
# Grind clinker into a fine powder.
# Add  gypsum (CaSO₄·2H₂O) equal to 5% by weight and grind again to make true cement.

== Uses ==
Cement has a strong compressive strength and can be poured to fit any mold. this versatility has led to widespread use in construction including roads, buildings, bridges, and more. 

== Dependencies ==

* [[Gravel]]
* [[Sand]]
** '''Cement'''
** [[Water]]
*** [[Concrete]]

== See also ==
* [[Concrete]]
* [[Gravel]]
* [[Lime mortar]]
* [[Mortar]]

== References ==
{{wa|Cement}}

== External links ==
* [https://primitivetechnology.wordpress.com/2018/07/17/wood-ash-cement/ Wood ash cement], primitivetechnology.wordpress.com. 17 July 2018.
* [https://www.youtube.com/watch?v=9L0i6YdTtoY How to make Cement From Snail's Shell] - Pre Technology, 14 October 2021, YouTube

[[Category:Building materials]]
[[Category:Stubs]]