Material

• Rebar is made from steel, typically carbon steel. However, to prevent rebar from rusting and degrading, it is sometimes made from stainless steel. Stainless steel contains chromium, which prevents rusting as well as corrosion, if the rebar is put into a location subject to corrosion. Steel containing chromium is often stronger than other types of steel, which makes it ideal for particularly large structures as well as locations that are prone to earthquakes. Some types of rebar are coated with epoxy, which also prevents corrosion.
  
  

Use

• Rebar is used to add strength to concrete and similar materials. Concrete has a high compression strength, but low tension strength, which means that it will collapse when under high tension. Rebar is used to compensate for this property. When building a structure that uses rebar, the rebar is put into place first and then the concrete is poured around it. The rebar inside allows builders to create very large, stable structures from concrete.
  
  

Physical Characteristics

• Rebar is formed with ridges along the sides. This is to help it stay in place inside of the concrete, as concrete will not bond or adhere to steel. These ridges increase the friction between the rebar and the concrete and makes use of the high compression strength of the concrete. The weight of the concrete also increases the friction against the rebar, holding it in place and adding stability to the structure. In addition, without these ridges, the rebar could, with enough force, be pulled from the concrete.
  
  

Thermal Characteristics

• Steel is ideal for use with concrete because of its thermal and conductive characteristics. When the external temperature changes, many materials expand and contract slightly. Rebar and concrete expand and contract at the same rate. If they expanded and contracted at different rates, then the rebar inside would crack or separate from the concrete. In addition, steel is a good heat conductor. Concrete heats as it sets, and the steel helps to distribute that heat evenly by conducting it to different parts of a structure.