Repair Techniques for the Upstream Face of Concrete Dams

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Title: Repair Techniques for the Upstream Face of Concrete Dams

Author(s): B. Durand, Y. Germain, J. Houde and S. Tremblay

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 1231-1246

Keywords: Exposure; repairs; tests; waterproofing.

Date: 7/1/1997

Abstract:
The aging of concrete dams is a major problem that is often the cause for partial or total repair of the structure. One of the most important parts of the dam to be repaired is the upstream face where.water infiltration through joints and cracks contributes significantly to the overall degradation. The usual repair technique consists in removing the damaged concrete then applying a new layer of either concrete with formwork and reinforcement or shotcrete. Whichever the case, however, the new concrete may be subjected to similar deterioration and also to adhesion problems. An alternative to this technique is to apply a durable watertight coating to the upstream face after removing the damaged concrete. The study described in this paper identifies various types of applicable coatings including metallic sheets, bitumen-based products and synthetic geomembranes (prefabricated or sprayed). The focus here is on the latter, which seem best suited to present needs. Eight geomembranes were subjected to tests designed to determine their characteristics and performance under different conditions : four prefabricated products (PVC-A, PVC-B, HDPE and SBS) and four sprayed (Polyurethane-A, Polyurethane-B, Methacrylate and Neoprene). The study was divided into two experimental phases. First, standard tensile, puncture and pull-off tests to verify the effects of freezing and thawing cycles, ultraviolet radiation and low temperatures on the mechanical properties of the products. Four products showing the best performance, namely PVC-B, Polyurethane-A, Polyurethane-B and Methacrylate, were selected for the second phase. Measurements of the shear strength to assess the adherence of ice to the geomembranes were conducted in a specially built test bench. In cold climates such as Canada’s, the ice that forms on the surface of the reservoir in winter applies complex forces (compression, shear and even tensile forces sometimes) on the upstream face of dams and can damage the protective geomembrane. The shear strength was therefore studied under various loads. The products tested yielded a similar performance, all substantially reducing the ice adherence on the dam face. It was concluded that the application of a geomembrane provides additional protection against the deleterious action of ice and therefore represents a valid technique for the repair of concrete dams in cold climates.