Editing Reinforced concrete (section)

===Materials===
{{see also|Concrete|Cement|Construction aggregate|Rebar}}
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Concrete is a mixture of coarse (stone or brick chips) and fine (generally sand and/or crushed stone) aggregates with a paste of binder material (usually [[Portland cement]]) and water. When cement is mixed with a small amount of water, it [[Hydration reaction|hydrates]] to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid shape.<ref>{{Cite book|url=https://www.worldcat.org/oclc/19553645|title=Materials principles and practice|page=61|date=1990|publisher=Materials Dept., Open University|others=Charles Newey, Graham Weaver, Open University. Materials Department|isbn=0-408-02730-4|location=Milton Keynes, England|oclc=19553645}}</ref><ref>{{Cite book|url=https://www.worldcat.org/oclc/20693897|title=Structural materials|page=357|date=1990|publisher=Materials Dept., Open University|others=George Weidmann, P. R. Lewis, Nick Reid, Open University. Materials Department|isbn=0-408-04658-9|location=Milton Keynes, U.K.|oclc=20693897}}</ref> The aggregates used for making concrete should be free from harmful substances like organic impurities, silt, clay, lignite, etc. Typical concrete mixes have high resistance to [[compression (physical)|compressive]] [[stress (physics)|stress]]es (about {{convert|4000|psi|MPa|abbr=on}}); however, any appreciable [[tension (mechanics)|tension]] (''e.g.,'' due to [[bending]]) will break the microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension.

If a material with high strength in tension, such as [[steel]], is placed in concrete, then the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A composite section where the concrete resists compression and reinforcement "[[rebar]]" resists tension can be made into almost any shape and size for the construction industry.