<P> Rebar (short for reinforcing bar), collectively known as reinforcing steel and reinforcement steel, is a steel bar or mesh of steel wires used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and hold the concrete in compression . Concrete is strong under compression, but has weak tensile strength . Rebar significantly increases the tensile strength of the structure . Rebar's surface is often patterned to form a better bond with the concrete . </P> <P> The most common type of rebar is carbon steel, typically consisting of hot - rolled round bars with deformation patterns . Other readily available types include stainless steel, and composite sections made of glass fiber, carbon fiber, or basalt fiber . These alternate types tend to be more expensive or have lesser mechanical properties and are thus more often used in specialty construction where their physical characteristics fulfill a specific performance requirement that carbon steel does not provide . In practice, any material with sufficient tensile strength that is materially compatible with concrete could potentially be used to reinforce concrete, for example bamboo might be considered a viable substitution in regions where steel is not available . Steel and concrete have similar coefficients of thermal expansion, so a concrete structural member reinforced with steel will experience minimal stress as the temperature changes . </P> <P> Reinforcing bars in masonry construction have been used since at least the 15th century (2,500 meters of rebar was used in the Château de Vincennes). During the 18th century, rebar was used to form the carcass of the Leaning Tower of Nevyansk in Russia, built on the orders of the industrialist Akinfiy Demidov . The cast iron used for the rebar was of high quality, and there is no corrosion on the bars to this day . The carcass of the tower was connected to its cast iron tented roof, crowned with one of the first known lightning rods . However, it was not until the mid-19th century that rebar displayed its greatest strengths with the embedding of steel bars into concrete, thus producing modern reinforced concrete . Several people in Europe and North America developed reinforced concrete in the 1850s . These include Joseph - Louis Lambot of France, who built reinforced concrete boats in Paris (1854) and Thaddeus Hyatt of the United States, who produced and tested reinforced concrete beams . Joseph Monier of France is one of the most notable figures for the invention and popularization of reinforced concrete . As a French gardener, Monier patented reinforced concrete flower pots in 1867, before proceeding to build reinforced concrete water tanks and bridges . </P> <P> Ernest L. Ransome, an English engineer and architect who worked in the United States, made a significant contribution to the development of reinforcing bars in concrete construction . He invented twisted iron rebar, which he initially thought of while designing self - supporting sidewalks for the Masonic Hall in Stockton, California . His twisted rebar was, however, not initially appreciated and even ridiculed at the Technical Society of California, where members stated that the twisting would weaken the iron . In 1889, Ransome worked on the West Coast mainly designing bridges . One of these, the Alvord Lake Bridge in San Francisco's Golden Gate Park, was the first reinforced concrete bridge built in the United States . He used twisted rebar in this structure . </P>

When did they start using rebar in concrete