[3] Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure.

For a strong, ductile and durable construction the reinforcement needs to have the following properties at least: French builder François Coignet  [fr ] was the first one to use iron-reinforced concrete as a building technique.

[4] In 1853, Coignet built for himself the first iron reinforced concrete structure, a four-story house at 72 rue Charles Michels in the suburbs of Paris.

[5][11] Joseph Monier, a 19th-century French gardener, was a pioneer in the development of structural, prefabricated and reinforced concrete, having been dissatisfied with the existing materials available for making durable flowerpots.

In 1877, Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders, using iron rods placed in a grid pattern.

[13] Before the 1870s, the use of concrete construction, though dating back to the Roman Empire, and having been reintroduced in the early 19th century, was not yet a proven scientific technology.

[15] One of his bridges still stands on Shelter Island in New Yorks East End, One of the first concrete buildings constructed in the United States was a private home designed by William Ward, completed in 1876.

[20][21] In 1906, a partial collapse of the Bixby Hotel in Long Beach killed 10 workers during construction when shoring was removed prematurely.

Two years later, El Campanil survived the 1906 San Francisco earthquake without any damage,[24] which helped build her reputation and launch her prolific career.

In 1908, the San Francisco Board of Supervisors changed the city's building codes to allow wider use of reinforced concrete.

When cement is mixed with a small amount of water, it hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid shape.

The relative cross-sectional area of steel required for typical reinforced concrete is usually quite small and varies from 1% for most beams and slabs to 6% for some columns.

[32] The reinforcement in a RC structure, such as a steel bar, has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity, slip or separation of the two materials under load.

This load transfer is achieved by means of bond (anchorage) and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface.

However, if the actual available length is inadequate for full development, special anchorages must be provided, such as cogs or hooks or mechanical end plates.

[34] Zinc phosphate slowly reacts with calcium cations and the hydroxyl anions present in the cement pore water and forms a stable hydroxyapatite layer.

[35] Steel-reinforced concrete moment-carrying elements should normally be designed to be under-reinforced so that users of the structure will receive warning of impending collapse.

The reinforcing steel in the bottom part of the beam, which will be subjected to tensile forces when in service, is placed in tension before the concrete is poured around it.

However, carbonated concrete incurs a durability problem only when there is also sufficient moisture and oxygen to cause electropotential corrosion of the reinforcing steel.

However it is now known that when these materials come into contact with moisture they produce a weak solution of hydrochloric acid due to the presence of chlorides in the magnesite.

This a reaction of amorphous silica (chalcedony, chert, siliceous limestone) sometimes present in the aggregates with the hydroxyl ions (OH−) from the cement pore solution.

[42] Sulfates (SO4) in the soil or in groundwater, in sufficient concentration, can react with the Portland cement in concrete causing the formation of expansive products, e.g., ettringite or thaumasite, which can lead to early failure of the structure.

The most typical attack of this type is on concrete slabs and foundation walls at grades where the sulfate ion, via alternate wetting and drying, can increase in concentration.

Fiber-reinforced normal concrete is mostly used for on-ground floors and pavements, but can also be considered for a wide range of construction parts (beams, pillars, foundations, etc.

[43] Steel is the strongest commonly available fiber,[citation needed] and comes in different lengths (30 to 80 mm in Europe) and shapes (end-hooks).

Basalt fiber is stronger and less expensive than glass, but historically has not resisted the alkaline environment of Portland cement well enough to be used as direct reinforcement.

For one thing, concrete is a highly alkaline environment, in which many materials, including most kinds of glass, have a poor service life.

Deflection limits are set to ensure that crack widths in steel-reinforced concrete are controlled to prevent water, air or other aggressive substances reaching the steel and causing corrosion.

FRP rods also have relatively lower compressive strengths than steel rebar, and accordingly require different design approaches for reinforced concrete columns.

There is growing interest in applying external reinforcement to existing structures using advanced materials such as composite (fiberglass, basalt, carbon) rebar, which can impart exceptional strength.