Laboratory study on rockbolt corrosion

The effect of long term exposure of full size bolts to corrosive environments is presented. A special test rig was used to test four bolts under different loading conditions. Four, X-grade identical corrosioin testing using acid sulphate water. the pH value of the curculated water varied between 3.4 and 4.3. The corrosion exposure test period lasted three and half years. Two bolts were axially loaded to 10 and 20 tonnes force respectively, the third bolt was subjected to a 360 Nm torsion load and the fourth bolt was left unstressed to act as a reference bolt. After the test period ended, the bolts were strippd of their coroded coatings and weighted for weight loss. The diameter of each bolt was subsequently measured, and the loaded bolt samples were first tested non-destructively for tensile cracks and then tested for tensile failure. No cracks were found on post corrosion bolts tested non-destructively. The failure strength reduction onall four post-corroded bolts was significant, varying between 21 per cent and 39 per cent. The onset of corrosion was not confined to the targeted mid-section length of the bolt, however, the severest corrosion occurred a tthe anchored ends of the bolts.