Reinforced concrete: steel is embedded in concrete in such a way that the two materials combinedly act together in resisting forces.
The reinforcing steel could be in the form of rods, bars or mesh and absorbs the tensile, shear, and sometimes the compressive stresses in a concrete structure.
In 19th century the invention of concrete took the construction industry by storm it changed the way we built our urban jungles and in no time, it became one of the world’s most common building materials.
But this concrete had its own shortcomings, it couldn’t easily withstand tensile and shear stresses caused by wind, earthquakes, vibrations and is therefore unsuitable in most of structural applications.
Then the reinforced concrete came into picture, in reinforced concrete, the tensile strength of steel and the compressive strength of concrete work together to allow the member to sustain these stresses over considerable spans.
The above figure illustrates the failure of plain concrete beam.
Following are the major reasons for using Steel rebars:
- Steel is highly ductile material. It could be deformed without ever losing its toughness
- Young’s Modulus of steel is equal in both tension and compression (2.0 – 2.1 x 105 N/mm2). It means increase/decrease in length of steel bar on pulling/pushing will be same.
- Coefficient of thermal expansion (increase in length corresponding to increase in temperature) of concrete and steel is almost equal. This ensures the bond strength during thermal expansion, thus preventing bond failure. Moreover, if not same the bar will contract/expand more than concrete and will create problem.
- Steel undergoes the same strain or deformation as the surrounding concrete in order to prevent discontinuity, slip or separation of the two materials under load.
- It can be recycled easily
- It can be welded easily.
- Widely and cheaply available compared to other ductile metals.
Seeing above advantages, it can be said that using steel for reinforcement is the best alternative for Reinforced Concrete.
Effects of steel on concrete: