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Concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concrete's behavior, rebar is cast into it to carry the tensile loads. Most steel reinforcement is divided into primary and secondary reinforcement:
However, other materials are often used to reinforce concrete e.g. organic and inorganic fibres, composites in different forms. While compared to its compressive strength, concrete is weak in tension. Thus adding reinforcement increases the strength in tension.
Rebar is the most common form of concrete reinforcement. It is typically made from steel, manufactured with ribbing to bond with concrete as it cures. Rebar is versatile enough to be bent or assembled to support the shape of any concrete structure. Carbon steel is the most common rebar material.
Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed (concrete in compression, reinforcement in tension), so as to improve the behavior of the final structure under working loads.
Initiation and propagation periods of steel rebar corrosion in a reinforced concrete structure (Tutti diagram). [2] [3] Initially, the chemical reactions that normally occur in the cement paste, generate an alkaline environment, bringing the solution in the cement paste pores to pH values around 13. In these conditions, passivation of steel ...
A Johnson bar (also Johnson corrugated bar) is a type of corrugated high-carbon steel [1] rebar used to reinforce concrete.. The Johnson bar was invented by A.L. Johnson [2] of the St. Louis Expanded Metal Company.
The rebar spacers are fixed before the concrete is poured and remain within the structure. The main categories of rebar spacers are: Linear Spacers (Section profiles, H-section profiles, or 3-dimensional shapes), Point Spacers (wheel spacers, various tower or chair-like shapes) Rebar spacers can be divided into three raw materials categories:
Example of flat piece of concrete having dislodged with corroded rebar underneath, Welland River bridge across Queen Elizabeth Way in Niagara Falls, Ontario. The expansion of the corrosion products (iron oxides) of carbon steel reinforcement structures may induce internal mechanical stress (tensile stress) that cause the formation of cracks and disrupt the concrete structure.