Effective cover of reinforcement refers to the distance between the outer surface of the concrete and the nearest surface of the reinforcing bar or wire. It is an important factor in the design and construction of reinforced concrete structures as it helps protect the reinforcement from corrosion, fire, and other external factors. The correct answer to the given question is option 'D', which states that the clear cover should be half the diameter of the reinforcing bar.

Explanation:

Clear cover is the minimum distance between the outer surface of the concrete and the nearest surface of the reinforcing bar. It is important to provide an adequate clear cover to prevent the reinforcement from coming into direct contact with external elements that can cause corrosion or damage. The clear cover is typically specified in the design codes or standards.

The clear cover requirements are based on several factors such as the type of structure, exposure conditions, and the diameter of the reinforcing bar. The clear cover should be sufficient to provide protection to the reinforcement while also ensuring proper bond between the concrete and the reinforcement.

The given option 'D' states that the clear cover should be half the diameter of the reinforcing bar. This means that if the diameter of the bar is 'd', then the clear cover should be (1/2) * d.

Advantages of Option 'D':

1. Adequate protection: Providing a clear cover of (1/2) * bar diameter ensures sufficient protection to the reinforcement by keeping it away from the external environment. This helps in preventing corrosion and other forms of damage.

2. Proper bond: The clear cover also plays a crucial role in ensuring proper bond between the concrete and the reinforcement. By providing a clear cover of half the bar diameter, the concrete is able to properly surround and grip the reinforcement, enhancing its load-carrying capacity.

3. Easy construction: Option 'D' provides a clear and straightforward guideline for the design and construction of reinforced concrete structures. Contractors and engineers can easily determine the clear cover by simply measuring the diameter of the reinforcing bar and dividing it by 2.

In conclusion, the effective cover of reinforcement should be equal to half the diameter of the reinforcing bar. This provides adequate protection to the reinforcement and ensures proper bond between the concrete and the reinforcement. It is important to adhere to the specified clear cover requirements to ensure the durability and longevity of reinforced concrete structures.