Lifetime assessment of exposed PVC-P geomembranes installed on Italian dams

The aim of this paper is to study the performance of plasticised polyvinyl chloride (PVC) geomembranes used in the rehabilitation of concrete and masonry dams. In such applications, the geomembranes are left exposed on the upstream face, without external protection, to environmental factors and weather conditions, especially to UV rays. Evaluation of the performance and the lifetime assessment of the geomembranes is very important from a managerial point of view. Therefore, the results from a 25-year ongoing study on the long-term performance of PVC-P geomembranes installed on the upstream face of Italian dams are presented. The sampled geomembranes have been subjected to physical and mechanical tests and the results interpreted with reference to the variation of plasticiser, tensile characteristics, foldability at low temperatures, volumic mass and water vapour permeability. In the analysed samples, the loss of plasticiser range from 14.83% to 21.86%. This decrease in plasticiser content resulted in slightly higher modulus and tensile strength. The functionality of the geomembranes was not affected, as evaluated also by on site inspection. On the basis of the experimental results, lifetime predictions of the exposed geomembranes using the function of the loss of plasticiser were made.