a prescribed prestressing process is employed to construct precast concrete beams and girders . the process is utilized where an early concrete strength is too low for transfer of the full pre - tensioning force on a daily schedule to avert an otherwise serious and costly production delay . the process described provides the producer a reliable way of making beams and girders that are prestressed to take advantage of the higher concrete strength characteristics . the consequent economic advantage of higher structural capacity beams and girders is thereby realized . additionally , beam or girder camber is controlled by the process , fostering production of a superior quality product .