Geomembrane installations often cover substantial areas. Landfill cells pose enormous footprints. Oil and gas pits, industrial processing ponds, and wastewater containment ponds are large installations too, and each year they tend to be built a little larger. The scaling up of these facilities is not just a matter of achieving better operational economics for the facility owner; it’s also because geosynthetic materials perform well and strong installation practices continue to prove that another leap in project scale is attainable.
Alongside these changes to the scale of installations is the constant refinement that occurs in geomembrane manufacturing.
You can see the result of a major shift in manufacturing in many of the photos you might encounter from large lining projects. Increasingly, the materials are lighter. Instead of their traditional black color, they being specified and supplied in white, tan, and lighter gray shades.
ADVANTAGES OF LIGHTER COLORS
Lighter colored geomembranes provide some important advantages in a large installation. A solar-reflecting (white) surface reduces thermal expansion of the materials. Black liners that must be welded in the field (e.g., HDPE and LLDPE) require slack to be built into the system and the liners must be left to warm a bit in the sun before panel joining activities take place. The expansion that occurs, if not properly accounted for, could lead to wrinkles in the geomembrane system, which would subsequently pose an increased risk for damage or complicate detecting damage.
Also, when these geomembranes are installed over a geosynthetic clay liner (GCL) layer, the thermal fluctuations in a black geomembrane as it warms and cools while exposed can pull water from the soil beneath the geomembrane. This can incite a desiccation process in the GCL zone.
In better managing the impact of uv light, solar-reflecting layers can extend the life of a geomembrane by slowing surface degradation.
Furthermore, products with white layers atop black can help visually identify damage, as the black layer will show if the white surface is damaged.
Whether exposed only during the installation process or serving as an exposed liner, reflective geomembranes offer a number of practical benefits that can lead to real long-term performance advantages.
ARE THEY AS UV RESISTANT?
Carbon black is deservedly renowned for enhancing UV resistance in various materials, and it has been a major component of the success of geomembranes. But, carbon black isn’t used exclusively for surface stabilization against uv light; and there there are other ways stabilize materials.
Advances in the additive packages used in manufacturing have enabled producers to use custom formulations with light stabilizers other than carbon black on the surface. Quality control and testing programs, in-house and with independent verification, have helped manufacturers achieve the same strong UV resistance in the surface layer of these geomembranes without the need for carbon black.
The carbon black is still generally present. Co-extruded white HDPE and LLDPE geomembranes, for example, typically feature white surfaces (textured or smooth) and a core of black geomembrane that is thicker than the white surface layer(s).