**2. Sustainable geosynthetics**

*Geopolymers and Other Geosynthetics*

*Functions of geosynthetics in soil structure.*

*Functions of geosynthetics for application.*

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**Figure 3.**

**Figure 1.**

**Figure 2.**

*Abbreviations and abbreviated definitions of geosynthetics.*

Most of the geosynthetics contribute to the long-term stability of the soil structure, so that products with small changes in long-term performance are mainly used, while demand for biodegradable products emphasizing planting and environmental compatibility is also increasing (**Figures 3** and **4**).

Therefore, sustainable geosynthetics mentioned in this chapter are classified as "Usual Geosynthetics" and "Green Geosynthetics" based on required performance as shown in **Figure 5** [6, 7].

First, environmental adaptive geosynthetics, which we have previously described as "Usual Geosynthetics," have not changed much over the past 20 years but have created a paradigm of composite products using extreme strength fibers with the keyword of diversification. The environmentally adaptable geosynthetics can be introduced as "Usual Geosynthetics," which are used to reinforce the ground structure, and the initial strength retention rate should be within the given range during the service life.

In other words, usual geosynthetics are a product that requires a high resistance to instantaneous loads from the outside and also requires a hybrid function that converges to the reinforcement, protection, and blocking functions that are the basic functions of geotextiles. Since natural fibers have the advantage of being eco-friendly

**Figure 4.**

*Examples of typical geosynthetic products.*

**Figure 5.** *Schematic diagram of "Sustainable Geosynthetics".*

materials, the utility of geotextile as a raw material has begun to be reemerged in recent years such as various types of cotton, jute, coir, and straw. However, since it is not used much and cannot be mass-produced compared to synthetic fibers, it has difficulties in creating demand. Some of them use natural geotextiles as slope stabilization, erosion prevention, and drainage, but here is no big change [4].

On the other hand, polyolefin (polyolefin) and polyester (polyolefin) are the most widely used synthetic polymer materials. Polyurethane, glass, and carbon polymers are very limited. Since the polymer materials used in the manufacture of geosynthetic products are often used in large quantities by low cost. In general, manufacturing high-performance geosynthetics increases the manufacturing cost, which is economically expensive. In other words, if the performance is the same, a product with a lower manufacturing cost is economically advantageous. Considering this, geosynthetics using recycled polymer materials may be considered, but disadvantages of performance decrease compared to geosynthetics using virgin polymers rather than recycling becomes a problem. Considering the environmental aspects, it is preferable to use recycled polymer materials, but the additional cost of recycling is not recommended in terms of economic performance.

High-performance hybrid polymer materials are being used as convergence geosynthetic products are required to protect, repair, and repair the ground structure from natural disasters such as earthquakes, tsunamis, and typhoons. These convergence geosynthetic products play a pivotal role in improving the stability of geotechnical structures and expanding their applications. Carbon fibers, aramid fibers, and liquid crystal polymer fibers are being used as new materials. In addition, test methods and construction techniques related to these new materials are being developed to expand the performance of these convergence geosynthetic products.

Second, "Green Geosynthetics" refer to products that have sustainable degradable geosynthetic fiber and environmental pollution prevention and restoration functions that do not mean long-term implementation of initial performance in terms of environmental friendliness.

For the slope stabilization/protection field requiring eco-environmental properties, mesh type geocell using biodegradable resin is applied to slope vegetation, river maintenance, eco-slope composition, garden-based layer, landfill slope, and waterproof protection. This reflects the demand for eco-environmental geosynthetics and means that there is a growing need to expand biodegradable geosynthetics to civil/environmental fields. In addition, polypropylene staple fiber products have been developed in the geosynthetics and web structures to emphasize the slope reinforcement function.

In the case of fiber, "biodegradability" means decomposition by microorganisms or bacteria in the soil, which is a geotechnical structure, and the initial performance gradually decreases during the service period [5].

In order to recover the contaminated environment and to manufacture "Green Geosynthetics," a biodegradable resin should be used as a raw material, and it is differentiated from geo-fiber, which cannot be decomposed after construction. Also, when used as a filter, manufacturing of geotextiles in the form of nanofibers helps improve filtration efficiency.
