Concrete

This article is about the construction material. For other uses, see Concrete (disambiguation).
Not to be confused with cement, grout, mortar, or plaster.

A single concrete block, as used for construction

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures to a solid over time. Concrete is the second-most-used substance in the world after water,[1] and is the most widely used building material.[2] Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.[3]

When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts with the water through a process called concrete hydration[4] that hardens it over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses.[5] This time allows concrete to not only be cast in forms, but also to have a variety of tooled processes performed. The hydration process is exothermic, which means ambient temperature plays a significant role in how long it takes concrete to set. Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. Most concrete is poured with reinforcing materials (such as steel rebar) embedded to provide tensile strength, yielding reinforced concrete.

In the past, lime-based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements, (water resistant) such as a calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone).[6][7] Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder. Concrete is distinct from mortar.[8] Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks, tiles and other masonry units together.[9] Grout is another material associated with concrete and cement. It does not contain coarse aggregates and is usually either pourable or thixotropic, and is used to fill gaps between masonry components or coarse aggregate which has already been put in place. Some methods of concrete manufacture and repair involve pumping grout into the gaps to make up a solid mass in situ.

  1. ^ Gagg, Colin R. (May 2014). "Cement and concrete as an engineering material: An historic appraisal and case study analysis". Engineering Failure Analysis. 40: 114–140. doi:10.1016/j.engfailanal.2014.02.004.
  2. ^ Crow, James Mitchell (March 2008). "The concrete conundrum" (PDF). Chemistry World: 62–66. Archived (PDF) from the original on 9 October 2022.
  3. ^ Manager, Samsung C&T Global PR (27 June 2018). "Concrete Matters: A Primer on the Most Popular Man-Made Material". Samsung C&T Newsroom. Retrieved 28 November 2023.
  4. ^ "Scientific Principles". matse1.matse.illinois.edu. Retrieved 24 May 2023.
  5. ^ Li, Zongjin (2011). Advanced concrete technology. John Wiley & Sons. ISBN 978-0-470-90243-1.
  6. ^ Industrial Resources Council (2008). "Portland Cement Concrete". www.industrialresourcescouncil.org. Retrieved 15 June 2018.
  7. ^ National Highway Institute. "Portland Cement Concrete Materials" (PDF). Federal Highway Administration. Archived (PDF) from the original on 9 October 2022.
  8. ^ Limbachiya, Mukesh C.; Kew, Hsein Y. (3 September 2008). Excellence in Concrete Construction through Innovation: Proceedings of the conference held at the Kingston University, United Kingdom, 9 - 10 September 2008. CRC Press. p. 115. ISBN 978-0-203-88344-0.
  9. ^ Allen, Edward; Iano, Joseph (2013). Fundamentals of building construction: materials and methods (Sixth ed.). Hoboken: John Wiley & Sons. p. 314. ISBN 978-1-118-42086-7. OCLC 835621943.