Reinforcement in a concrete structure accounts for one third of the cost of the structure. The fabrication of the bars, tendons, and meshes used for reinforcement adds almost 20-30% to the basic cost of steel. The construction industry’s contribution, therefore, is in the fabrication of these reinforcing elements and their placement in the formwork. Steel is the predominant reinforcement material used in concrete structures. It should be well embedded in concrete to impart tensile strength.
The best of structural designs can be ruined if the design and drawing are not carried out in the field as per the design assumptions and expectations. This highlights the need for the proper fabrication and effective placement of reinforcement during construction. Proper reinforced concrete construction depends upon the workforce on the job-those who understand and design the structures, those who know the characteristics and limitations of the materials that are handled at the site, and those who fabricate the reinforcements at the site.
Concrete is strong under compression but weak under tension and shear. Whenever concrete members are likely to be subjected to tension, they are reinforced with steel. Bars, mats, or cages of steel are used as reinforcement. These can be classified as active or passive. The active ones are those used for prestressing and the passive ones are those subjected to stress upon the application of loads. Concrete structures use reinforcements of different types: reinforcing bars-plain or ribbed, welded mesh, fibre reinforcement, and prestressing wires and strands. Steel is used as reinforcement in concrete owing to its following qualities.
- High tensile strength
- Good bond with concrete
- Nearly same coefficient of expansion as that of concrete
- Adequate quality control possible during the manufacture of steel