Abstract: A method of installing a tendon in a duct in a slip-formed concrete structure including the steps of providing a tubular member which forms the uppermost part of the duct and whose upper end terminates at the level where the upper end of the tendon is to be anchored, said tubular member having outwardly extending abutment means at or adjacent its lower end, said abutment means being of such size and at such depth below the upper end of the tubular member as to enable the forces necessary to instal and support a tendon in the duct, at the time when the concrete structure reaches a height in the vicinity of the upper end of said tubular member, to be transmitted through the tubular member and distributed to the concrete structure by the abutment means at a level where the concrete has gained adequate strength for this purpose.