In which condition is the bond strength of coated reinforcement greatest?

The bond strength of coated reinforcement is greatest with wet mortar because the presence of moisture aids in the chemical adhesion and mechanical interlocking between the reinforcing steel and the surrounding concrete. When wet, the mortar can better penetrate the surface of the coating on the reinforcement, allowing for a more effective bond to form. This is essential in ensuring that forces are adequately transferred between the steel reinforcement and the surrounding concrete, resulting in improved structural performance.

In contrast, when the steel is warm, the heat may cause some initial thermal expansion, which could temporarily affect the fit and bond. Dry mortar does not provide the necessary moisture required for optimal adhesion, leading to a weaker bond. Lastly, minimal deformations in the reinforcement can reduce the surface area available for bonding, which can also lead to a weaker connection between the steel and the concrete, thereby diminishing bond strength.