having a thickness of 1 2 mm and that is constituted of carbon fibers and of epoxy resin it is determined that such a reinforcement makes it possible to take up a load over one portion of a concrete structure of the order of 2 5 tonnes when it is bonded to concrete over a length of 100 mm it is determined that the bonding of a reinforcement to a portion of concrete structure as illustrated in fig2 where the fibers have been released from the matrix over a length of 100 mm and where l 2 2l 1 makes it possible to substantially double the load taken up by the reinforcement according to other embodiments illustrated in fig7 to 10 the rearrangement of the fibers released from the polymer matrix of the reinforcement consists in positioning these fibers in a mold and in mixing them with a polymer matrix in order to form by molding a reinforcement portion 25 26 27 28 29 having a shape different from the initial shape of the reinforcement of elongated shape for example in lamellar form 17 18 19 it is also possible to envision forming a reinforcement portion by mixing fibers released from the initial polymer matrix with a polymer matrix by any other forming method other than molding suitable for the manufacture or a composite portion such as for example extrusion or pultrusion fig7 represents a schematic view of a molding device 50 comprising a portion 51 that makes it possible to support a reinforcement in lamellar form 17 and a portion 52 comprising a cavity 53 into which the fibers of said reinforcement previously released from the polymer matrix are introduced these fibers are placed in.