Flat strip, in particular for the reinforcing ducts, method for making same, and ducts reinforced therewith

A flexible flat strip, comprising:

• at least one layer of longitudinal filamentary rovings agglomerated with one another in the form of a relatively flat bundle with a substantially rectangular cross-section;
• a retaining sheath surrounding and clamping the layer of filamentary rovings;
• and
• a binding material arranged at least at the interface of the retaining sheath and the longitudinal filamentary rovings;
• wherein the retaining sheath comprises connecting elements connecting the upper and lower surfaces of said flat strip through the bundle of longitudinal rovings over the entire length of said flat strip,
• wherein each longitudinal filamentary roving has a global average compactness of at least 60% and a maximum void percentage of 15%, and
• wherein the flexible flat strip, after compression, has a shortfall lower than 25%.