Long Term Performance Requirements for HDPE Drainboards

Drainboards are gaining more and more interest in residential and commercial construction, as well as in the civil engineering industry for their ability to control ground water and protect foundation walls against moisture, reduce/eliminate hydrostatic water pressure on tunnel linings, provide a waterproof membrane as well as either an air gap and/or an open drainage channel on buried structures such as foundation walls. The main objective of these products is to eliminate infiltration of water into the construction, to avoid fungus growth in basements, and to control the humidity of the protected structure’s materials in order to decrease their rates of degradation. In order to provide adequate performance and protection for the construction, the product must maintain its full integrity over the entire design life of the structure. However, it appears that current product specifications completely avoid any reference to durability and long-term performance properties of these products, although many HDPE drainboards available on the market are manufactured with recycled polyethylene, either in part or in whole. The first section of this paper describes essential advantages and possible concerns associated with the usage and design with dimple sheets and drainboards. In the second section, the common degradation mechanisms associated to HDPE sheets are described. The third section presents two years of laboratory investigations conducted on HDPE dimple sheets, focusing on the aging mechanisms identified in the second section. Details associated twith the test procedures that have been developed to reflect the specific geometrical properties of dimpled sheets are presented as well as the results obtained. Finally, a summary table presenting recommended product specifications needed to confine the aging properties of drainboards and to design a system that performs adequately throughout the entire lifetime of the structure is provided.