People tend to view concrete as being a strong and durable material, but in reality it has several shortcomings. The two main areas where concrete falls short is its 'tensile strength' and its 'ductility.' An object's tensile strength is its susceptibility to breaking when it gets pulled apart by its two ends (or elongated). An object's ductility is its ability to withstand rupturing while undergoing plastic deformation (or being bent). In short, concrete is unfortunately brittle.

 

Concrete, however, can be reinforced to make it stronger. Steel bars called 'rebar' are placed inside the concrete while it is forming to give it greater tensile strength and ductility. If you were to watch the building process for reinforced concrete from beginning to end, you would first see a steel cage built and then a concrete block be cast surrounding it. Usually the steel bars will be corrugated (grooved at regular intervals) to make the bond between the concrete and the steel more substantial.

 

There are two ways to make reinforced concrete even stronger: 'pre-stressing' and 'post-stressing.' Pre-stressing involves adding tension to the materials during the building process - the steel bars are held firmly in place as the concrete sets and the setting concrete is compressed to make it grow more solid. When pieces of rebar are pulled taut during the construction of reinforced concrete, they are called 'tendons.' Post-stressing involves added permanent elements to the building or piece of infrastructure that will keep the rebar under tension and the concrete compressed.

 

In a symbiotic manner, the concrete in a piece of reinforced concrete protects the steel as the steel strengthens the concrete. Steel begins to corrode when it is subjected to a substance that has a pH level (acidity) below 10. Cement paste is party made up of alkaline chemicals, which have a high pH level. Reduction of corrosion due to the elements is called 'passivating.' Cement, which has a pH between 12.5 and 13.5, forms a passivating film around steel in reinforced concrete.