What is bond stress of concrete?

Bond stress is the result of the bonding between the concrete surface and the reinforcement steel. It varies depending upon the type of concrete and type of reinforcement used. If plane rounded steel is used as reinforcement then the bond stress will be less, if same concrete is used with HYSD steel as reinforcement then the bond stress is higher.

In Simple terms it is like grip, more grip if surface is rough and less grip if surface is smooth and rounded.Bond stress is defined as the shear force per unit of Nominal surface area of a reinforcement bar acting parallel to the bar on the interface between the bars and surrounding concrete.
The bond between steel and concrete is mainly due to pure adhesive resistance, frictional resistance and mechanical resistance.
The bond stress developed in concrete around the steel reinforcement is given by

Design bond stress

• For deformed bars these values shall be increased by 60 percent.
• For bars in compression can be increased by 25 percent.

To read or learn more about bond stress and important points about bond stress go to Bond stress and Development length