An apparatus is configured to de-ice a surface of a casing tube of a tendon that is exposed to weather influences, or to guard the case tube against ice forming on the case tube, where the tendon is anchored to a structure by an anchoring device. The apparatus includes a power device, one end of which is directly or indirectly in force transmitting engagement with the anchoring device and the other end is directly or indirectly in force transmitting engagement with the casing tube. The power device is configured to move the casing tube relative to the anchoring device in the circumferential, radial and/or axial direction in relation to the longitudinal extension direction of the casing tube.