Question

If concave mirror is broken then what happens to radius of curvature

Answer 1

Nothing.

When the concave mirror is broken, the individual pieces are essentially smaller parts of the same spherical mirror.

If you imagine it like an egg shell, which is spherical in shape, the different pieces of the broken egg shell represent the concave mirror. But that will not change radius of curvature

Radius of curvature remains the same.

Hope this helps :)