Tension indicator for a rock bolt

A tension indication device for a rock bolt, the rock bolt including a central rod with a trailing portion provided with a nut, the tension indication device comprising:

• a support washer provided with a central hole arranged for receiving the trailing portion of the rock bolt;
• a cover member with a central hole arranged for receiving the trailing portion of the rock bolt;
• and
• an indicator substance provided in a first space, wherein
• a) the first space is provided in the cover member and wherein the indicator substance is radially outwards surrounded by a circumferential wall portion of the cover member extending about a central axis of the tension indication device, and wherein the circumferential wall portion is configured such that it is deformable by the nut upon tensioning of the central rod upon rotation of the nut such that the nut at least partly enters the first space, or
• b) the first space is provided in a recess in the support washer for facing the nut, wherein the cover member is configured to be fitted between the nut and the support washer and to normally cover the recess such that the indicator substance is not visible before tensioning of the central rod by rotation of the nut, wherein the first space is cylindrical and radially inwardly open, and wherein the first space is in the cover member and the circumferential wall portion includes slits or weakened portions.