Plain concrete is weak in tension and strong in compression. Tensile property for concrete structures is obtained by incorporating steel reinforcement. The steel reinforcement is strong in both tension and compression. The tensile property provided by the steel reinforcement will prevent and minimize concrete cracks under tension loads. The coefficient of thermal expansion of steel reinforcement and concrete are similar in that they undergo similar expansions during temperature changes. This property will ensure that the concrete is subjected to minimal stress during temperature variations. The surface of the steel reinforcement bars is patterned to have a proper bond with the surrounding concrete material. The two main factors that provide strength to the concrete structures are steel and concrete. The design engineer will combine both the elements and design the structural element such a way that the steel resists the induced tensile and shear force, while the concrete takes up the compressive forces.
Designations, diameters, areas and weights of standard bars.
| Bar No. (in) | Bar No. (mm) | Diameter (in) | Cross-Sectional Area (in2) | Nominal Weight (kg/ft) |
|---|---|---|---|---|
| 3 | 10 | 0.375 | 0.11 | 0.170 |
| 4 | 13 | 0.500 | 0.20 | 0.303 |
| 5 | 16 | 0.625 | 0.31 | 0.473 |
| 6 | 19 | 0.750 | 0.44 | 0.681 |
| 7. | 22 | 0.875 | 0.60 | 0.927 |
| 8 | 25 | 1.000 | 0.79 | 1.211 |
| 9 | 29 | 1.128 | 1.00 | 1.542 |
| 10 | 32 | 1.270 | 1.27 | 1.952 |
| 11 | 36 | 1.410 | 1.56 | 2.410 |
| 14 | 43 | 1.693 | 2.25 | 3.470 |
| 18 | 57 | 2.257 | 4.00 | 6.168 |
