Performance of different joining techniques used in the repair of bituminous waterproofing membranes

- Repair actions on aged OB membranes are discouraged.
- APP membrane joints showed little susceptibility to ageing of one of the membranes.
- Adhesive bonds were the most reliable and effective for repairing APP membranes.
- SBS membrane specimens failed mostly outside the joint and within the membrane.
- The flexibility/brittleness of SBS membranes should be evaluated prior to repair.

This paper presents an experimental investigation on the performance of different techniques for executing joints between aged and new bituminous membranes in order to evaluate the performance of waterproofing repair systems. Three different types of fibre reinforced membranes were considered: (i) oxidised bitumen membranes, (ii) APP-modified bitumen membranes; and (iii) SBS-modified bitumen membranes. The membranes were aged by heat weathering in a thermal chamber at 70 °C, for periods of 4, 16 and 24 weeks. To simulate the repair operations, new (unaged) membranes were subsequently bonded to the artificially aged membranes either by (i) adhesive bonding or (ii) heat welding using a gas blowtorch. The membranes were tested in tension, and the joint specimens were subjected to shear and peeling tests. The results obtained show that regardless of the joining technique the joints between oxidised bitumen membranes are significantly affected by heat ageing of one of the membranes, particularly in peeling. APP membrane joints proved to be less susceptible to the effects of ageing; the behaviour of adhesive and welded joints was different, with the former joints exhibiting higher deformability. The joints between new and aged SBS membranes were consistently stronger than the membranes themselves, with failure typically occurring at the aged SBS membrane; the results obtained confirm that these membranes are significantly affected by heat ageing.