concrete

concrete. Building material made by mixing fragments of hard material (aggregate—usually broken stone) with mortar (fine aggregate—usually sand, water, and a binding-agent—now usually Portland cement). Historically, concrete was made with lime, sand, and water, with brick-dust, crushed volcanic rock, and other materials added. A type of concrete was used in Roman construction called opus caementicium, consisting of undressed stones bedded in a mix of lime and pozzolan, which dried out quickly, so had to be laid in courses. By C1 ad the drying-out process could be retarded, thanks to the evolution of slow-drying mixes, and this facilitated the evolution of huge vaulted structures covering vast spaces. The Romans used types of concrete made of lime, with tufa (porous, light, volcanic rock found around Rome) and other aggregates for these vaults, often in association with brick or stone reinforcement, and this created an architecture where the inner volumes were more important, perhaps, than the exteriors. Early examples of Roman architecture covered by concrete vaults are the Domus Aurea (Golden House) by Severus, and the enormous Pantheon in Rome, with its coffered dome

Types of concrete were in use for Byzantine structures but fell from favour until revived in C18, notably in France and England. Concrete was used by Smirke in the structure of the British Museum, and concrete laid over hollow-brick vaulting was used by Henry Roberts for fire-proof construction in work-ing-class housing during the 1850s. The discovery by Joseph Aspdin (1779–1855) of Portland cement made from lime and clay facilitated the development of immensely strong concrete structures as well as the evolution of a scientifically based theory. Strong in compression, concrete is weak in tension, so the weakness has to be eliminated if concrete is to be used in members subjected to tension, such as beams. Reinforcement with metal was experimented with in the early C19, and Loudon (1832) recorded concrete floors reinforced with interlacing iron bars. Other pioneers include Coignet, Monier, and Louis-Joseph Vicat (1786–1861—who produced cements that set under water, and classified them as ‘hydraulic’), William E. Ward (1821–1906—who built a concrete house at Chester, NY, in 1873), and Thaddeus Hyatt (1816–1901). The last two published theoretical works in the USA in the 1870s, but the theoretical basis for reinforced concrete evolved from the early work of William Boutland Wilkinson (1819–1902—who patented a reinforced-concrete floor system in 1854), and Joseph-Louis Lambot (1814–87— who exhibited his system of wire-mesh reinforced concrete at the 1855 Exposition Universelle, Paris). Monier licensed his patents in Germany in 1885 through Gustav Adolf Wayss (1850–1917), who in turn commissioned Matthias Koenen (1849–1924) to research the theory of reinforced concrete, but a major advance came when Hennebique developed concrete reinforced with steel (1892). In the USA advances were made by Ernest L. Ransome (1884–1911) and Albert Kahn, leading to standardization and the mass-production of building components.

Baudot's church of St-Jean de Montmartre, Paris (1894–1902), employed steel reinforcement in its brick-and-concrete construction, and Maillart evolved designs for reinforced-concrete buildings from 1905, developing the theme of unified pier and vault known as mushroom slabs. Max Berg constructed the huge Jahrhunderthalle (Century Hall) in Breslau (now Wrocław) of reinforced concrete in 1910–13, and Auguste Perret began using reinforced concrete almost from the beginning of his career with the Rue Franklin flats, Paris (1903–4). The Royal Liver Building, Liverpool (1908–10), by W. Aubrey Thomas (1859–1934), is an early British example of reinforced-concrete construction on the Hennebique principle, while the same architect's Tower Buildings, near by (1908), expresses the frame more clearly, and is clad in faïence. Reinforced concrete enabled very large cantilevers to be constructed, but its major advantages were that it was capable of withstanding great compressive and tensile loads (as steel can), but with the important advantage of a high degree of fire-resistance. The evolution of complex reinforced-concrete structures was pioneered by Freyssinet with his bridges and parabolic vaults. In later times, Candela and Nervi further developed reinforced-concrete structures (see béton).

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