Concrete

Concrete is a <a href="/facts/Composite_material/UBysQldh">composite material</a> composed of <a href="/facts/Construction_aggregate/K7XM0BAg">aggregate</a> bound together with a fluid <a href="/facts/Cement/VfDMkk12">cement</a> that <a href="/facts/Curing_(chemistry)/qHuInaQg">cures</a> to a <a href="/facts/Solid/YU0hJq6f">solid</a> over time. It is the second-most-used substance (after <a href="/facts/Water/0lkXnJPK">water</a>), the most–widely used building material, and the most-manufactured material in the world.
When aggregate is mixed with dry <a href="/facts/Portland_cement/kPj8EjnP">Portland cement</a> and <a href="/facts/Water/0lkXnJPK">water</a>, the mixture forms a fluid <a href="/facts/Slurry/erSTjthc">slurry</a> that can be poured and molded into shape. The cement reacts with the water through a process called hydration, which hardens it after several hours to form a solid matrix that binds the materials together into a durable stone-like material with various uses. 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 <a href="/facts/Exothermic_process/gCuSvpa4">exothermic</a>, which means that <a href="/facts/Room_temperature/NjHdkY4A">ambient temperature</a> plays a significant role in how long it takes concrete to set. Often, additives (such as <a href="/facts/Pozzolan/hYvjy2vQ">pozzolans</a> or <a href="/facts/Superplasticizer/Cj2YKte6">superplasticizers</a>) are included in the mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise modify the finished material. Most structural concrete is poured with reinforcing materials (such as steel <a href="/facts/Rebar/qm27fUbk">rebar</a>) embedded to provide <a href="/facts/Tensile_strength/Cv2jPplR">tensile strength</a>, yielding <a href="/facts/Reinforced_concrete/aUTUKAQF">reinforced concrete</a>.
Before the invention of Portland cement in the early 1800s, <a href="/facts/Lime_(material)/uMcVXGBM">lime</a>-based cement binders, such as lime putty, were often used. The overwhelming majority of concretes are produced using Portland cement, but sometimes with other <a href="/facts/Hydraulic_cement/VfDMkk12">hydraulic cements</a>, such as <a href="/facts/Calcium_aluminate_cements/6vGNN6Ak">calcium aluminate cement</a>. Many other non-cementitious <a href="/facts/Types_of_concrete/uhSh8hWW">types of concrete</a> exist with other methods of binding aggregate together, including <a href="/facts/Asphalt_concrete/TTp7fXA6">asphalt concrete</a> with a <a href="/facts/Bitumen/tW6EqphW">bitumen</a> binder, which is frequently used for <a href="/facts/Road_surface/m80ermWq">road surfaces</a>, and <a href="/facts/Polymer_concrete/zerqYUh3">polymer concretes</a> that use polymers as a binder.
Concrete is distinct from <a href="/facts/Mortar_(masonry)/UsDMxYAh">mortar</a>. Whereas concrete is itself a building material, and contains both coarse (large) and fine (small) aggregate particles, mortar contains only fine aggregates and is mainly used as a bonding agent to hold <a href="/facts/Brick/2CBPgDIK">bricks</a>, <a href="/facts/Tile/vk9El8Ty">tiles</a> and other masonry units together. <a href="/facts/Grout/bIHN5knM">Grout</a> is another material associated with concrete and cement. It also does not contain coarse aggregates and is usually either pourable or <a href="/facts/Thixotropic/SwtTPjlv">thixotropic</a>, 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.

Concrete open-in-new

Concrete