curved connection between transversal and or edge ribs nb nt 1 further said circular joint comprises two parallel walls that are concentric with radial traction plates that may be applied in a central position with respect to the area delimited by intersections of edge ribs and transversal ribs there is an opening for the passage of a containing rod further there are openings nf on edge ribs nb preferably of circular shape having one ore more diametrically opposite grooves nf 1 said openings nf are arranged along edge ribs nb regularly spaced and in such a position that if various modular formwork panels are coupled the corresponding openings nf of the coupled formwork pamnels are perfectly aligned different modular formwork panels are joined with suitable closing keys c fig2 3 show respectively as a side view and as a perspective view a closing key c comprising a cylindrical body c 1 with a handgrip c 2 at one end and two or more radial relieves c 3 at the opposite end body c 1 of closing key c has a shape that is essentially cylindrical with a diameter substantially equal to the diameter of opening nf of edge ribs nb of the modular.