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Which of the following is/are not the characteristic(s) of an ideal reinforcing material? A. It should be easily available in bulk at low prices. B. It should not possess high tensile stress and elasticity C. It should be free from loose mill scales, loose rust, and a coat of paint. 

Which of the following is/are not the characteristic(s) of an ideal reinforcing material? A. It should be easily available in bulk at low prices. B. It should not possess high tensile stress and elasticity C. It should be free from loose mill scales, loose rust, and a coat of paint.  Correct Answer Only B

Explanation:

Characteristics of ideal reinforcing material:-

  • It should be easily and cheaply available in bulk.
  • It should possess high tensile stress and elasticity.
  • Its thermal coefficient of expansion should be nearly equal to that of concrete to minimize thermal stress.
  • It should be free from loose mill scales, loose rust, and a coat of paint, which reduces the bond.
  • It should be capable of forming a perfect bond or grip with concrete so that stresses are transferred from one material to the other.
  • It should have a long and durable life so that it can render service for a longer time.

Note: 

Steel is used as an ideal reinforcing material because it has high tensile strength and elasticity. Also used as a deformed bar and twisted bar.

Deformed bar:

  • This type of bar has some- type of projections that act as keys for concrete and check the flipping of bars.
  • The deformations are spaced along the bar at equal distances and thus the bar develops a greater bond by mechanical resistance to sliding.

Twisted bars: 

  • Bond may also be improved by using twisted bars which are cold worked.
  • Cold twisted bars in­crease the yield stress by about 50% and thus save the reinforcing material by 33%.
  • The increase in stresses is due to the path of twist. The most suitable pitch is 9 cm. to 12 cm.
  • If the pitch exceeds 12 cm, the stress reduces.
  • In twisted bars, hooks are generally not provided and thus saving in steel and labor.
  • On account of increased bond strength, the struc­tures do not experience cracks. This is why twisted reinforce­ment is very useful for water retaining structures.

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