As with functions and characteristics, many geosynthetics also share common material composition. Yet, products described as sharing the same material may still differ greatly depending on their design, particular polymer formulation, and chemical additives. If you simply compare products all listed as being made from polyethylene, you’re not getting the full picture of how they differ in durability and chemical resistance. Low- and high-density polyethylene are quite different, and each new material adds dozens more variations to consider. Find out which materials are commonly used for each type of geosynthetic, so you know what to compare as you’re shopping around for the right products.
Geogrids and Geonets
Geogrids must be made from a tough, yet flexible polymer, since they’re woven from fine strands of rigid thread or yarn. Polyester is a common material used for both geogrids and geonets. However, this material isn’t always flexible enough for very steep or curved installations. Polyvinyl alcohol polymers offer greater flexibility but less stiffness for stabilizing effect. Polyethylene and polypropylene are also commonly used for this type of geosynthetic. These two options are good for installations where chemical resistance is needed. You’ll also find some geogrids where the individual fibers of polyester are coated with polyethylene for enhanced flexibility with greater tear and puncture resistance.
Geotextiles and Geomembranes
Geomembranes offer a wide variety of material options. High density polyethylene (HDPE) and low density polyethylene (LDPE) are two common options, and when they’re combined to provide the best features of each, they’re commonly known as reinforced polyethylene (RPE). Polyvinyl chloride (PVC) and thick rubber sheets known as EPDM are also widely used as liners and geomembranes for these kinds of projects. When it comes to geotextiles, both woven and non-woven options are made generally from polyester and polypropylene. These materials are durable enough to stay flexible, while holding a surprising amount of weight before tearing. They’re made from polymers that are spun or extruded into fibers before being woven or matted together.
Geocomposites
Since geocomposites all consist of at least two layers of different materials, they’re generally not made from a single polymer. Almost any combination of geomembranes, geogrids, geonets, and geotextiles can end up forming the composite. This means that you’re likely to see combinations of polypropylene, polyester, polyethylene, polyvinyl chloride, and related materials making up these products. The flexible membrane part of the composite must have the durability to withstand stretching and tearing, so the grids and nets installed in the composite are usually formed from a stiffer material.
Other Geosynthetics
Geofoams are almost exclusively made from polystyrene, although chemical additives are introduced to give the various foams different structural properties. This is the same polymer used for making basic Styrofoam blocks. However, the polystyrene used in geofoam is highly expanded. Expanded polystyrene (EPS) offers better drainage capacity due to small gaps between the foam particles and better crush resistance when buried underground. Despite all this strength and compression resistance, geofoams remain remarkably light due to this expanded design. This saves on shipping and transportation costs in addition to streamlining the installation process. Geopipes are made from harder forms of polymers like polyethylene. Without this rigidity, it would be too easy for the pipes to collapse under the weight of the soil and leave water backing up inappropriately instead of draining.
