# Bituminous geomembrane

Bituminous geomembrane (BGM) is a type of geomembrane consisting of a reinforcing geotextile to provide mechanical strength and elastomeric bitumen (often called asphalt in U.S.) to provide impermeability. Other components such as sand, a glass fleece, and/or a polyester film can be incorporated into the layers of a BGM. Bituminous geomembranes are differentiated from bituminous waterproofing materials used in buildings due in part to their wide roll width, which can exceed 5m, and their substantial thickness of up to 6.0mm.
These properties are designed for environmental protection, civil infrastructure, and mining applications.

## Properties

Typical Intrinsic Properties of Bituminous Geomembranes :
| Property | Standard | Units | Value | Application Relevance |
| Coefficient of Linear Thermal Expansion | ASTM D 696 | °C⁻¹ | 10$^{−5}$ | A low coefficient of thermal expansion prevents problematic wrinkling with exposure to temperature variation. |
| Density | ASTM D 792-20 | g/cm³ | 1.27 | High density (greater than water) is useful for submersed applications, limiting wind uplift, and safer installation in windy conditions. |
| Elongation at Break | ASTM D 7275 | % | >60 | Elongation capacity combined with tensile strength provides toughness allowing light traffic during installation and accommodating differential settlement in service. |
| Friction Angle (sand side) | NF EN 495-2 | ° | 39.5 | A high friction angle allows for safer installation and greater slope stability. |
| Cold Bending - Lowest Temperature | ASTM D 746 | °C | -20 | Cold bending relates to the ability to use and manipulate the geomembrane in cold conditions. |
| Water Permeability | ASTM E 96 | m/s | < 6.10⁻¹⁴ | The extremely low water permeability of a BGM aligns with the high standards typical of geomembranes. |
| Gas Permeability (Methane Transmission Rate) | ASTM D 1434-82 | m³/(m$^2$.d.atm) | < 2.10⁻⁴ | A useful index for gas barrier applications. |

## History

The earliest estimated use of bitumen dates back 40,000 years to the Paleolithic age and the historical use of bitumen as a waterproofing layer is extensive and well documented.
In 1926, successful experiments were conducted by the South Carolina Highway Department in which cotton fabric was installed on-site in combination with hot bitumen for road surface treatment. Continued experimentation and practical experience led to the development of prefabricated hessian woven fabrics with factory coated bitumen. Known as 'bithess' this material was made in significant quantities for rapid deployment in airfields and roads in World War II. By controlling the moisture content to maintain subgrade strength, this early geomembrane was credited by General William Slim to have played a significant role in the advance of the Burma campaign, a theater famous for its challenging jungle terrain and wet weather conditions.
Bitumen emulsion applied to polypropylene geotextiles was reported by Daniel W. Kappes P.E. to have been used in a Nevada heap leach mining installation as early as 1973. Published literature describing the modern development of the bituminous geomembrane can be traced back to the first double-liner system conceived of in 1974 by geosynthetics pioneer, J.P. Giroud. This novel bituminous geomembrane was made by spraying hot bitumen in-situ onto a polyester geotextile. Soon after these early installations, factory manufactured BGMs were developed with factory impregnation of bitumen into the geotextile allowing a high standard of quality control. Spray applied BGMs went entirely out of favor by 1988.
Partial List of Noteworthy BGM Projects :
| Project | Country | Type | Date Completed |
| Le Pont-de-Claix Water Reservoir | France | Water | 1974 |
| Ospedale Reservoir | Corsica | Water | 1978 |
| Parc des Chanteraines | France | Water | 1982, 2020 |
| Manche storage centre | France | Environmental Protection | 1994 |
| Ortolo Reservoir | Corsica | Water | 1996 |
| La Galaube Dam | France | Water | 2000 |
| Kildare Bypass | Ireland | Transportation | 2003 |
| Diavik Diamond Mine | Canada | Mining | 2007 |
| Kittilä mine | Finland | Mining | 2007, 2008 |
| Las Bambas copper mine | Peru | Mining | 2012, 2014 |
| Dolores mine | Mexico | Mining | 2013, 2014, 2017, 2020 |
| St. George Regional Airport | United States | Transportation | 2019 |
| Pench Right Canal | India | Water | 2019, 2022 |
| Stockton Mine | New Zealand | Mining | 2022 |