The same effect could be achieved by keeping the steel rods

The same effect could be achieved by keeping the steel rods at a higher temperature while the concrete cures and then allowing them to cool after the concrete had cured. Explain why this would again result in compression in the concrete

Solution

When the steel rods are heated to a hight temperature, expansion of the steel rods take place.So for this expansion length of steel rods, there will be a particular ;length of concrete which had cured. Therefore, when the rods are cooled to their original temperature, they will return to their original lengths. This will create some compressive stress in the concrete adjoint to the steel rods. Thus, the compression in the concrete occurs.