DL Construction said on the 24th that it has developed new technology for tunnel shotcrete using a PET fiber composite with a helix structure and a vibration dispersion system. A helix structure refers to fibers twisted into a spiral. The PET fiber composite is a plastic material processed into fiber.
The new technology is an innovation that surpasses existing steel fiber reinforcements in dispersion, constructability, durability, and safety, while also delivering eco-friendly effects. DL Construction jointly developed the technology with Union Mulsan and Donghae Engineering & Consultants.
Shotcrete is a method of construction that sprays concrete together with compressed air. It is mainly used for reinforcement of structures such as tunnels and underground structures, or for surface coating.
This new technology feeds a fixed quantity of the PET fiber composite through a vibration dispersion system and disperses it uniformly. Ordinary fiber composites have a low specific gravity, causing them to float when mixed with concrete. However, the PET fiber composite developed this time has a high specific gravity and does not float in water. It mixes well with concrete and does not clump, allowing it to deliver better performance than other fiber composites.
This can reduce the rebound rate (the ratio of material that bounces off instead of adhering to the surface when shotcrete is sprayed) to about 49.6%. Concrete production expense can also be reduced by 18.6%.
Soil and groundwater pollution are also reduced, waste disposal costs are cut, and recycling is possible by using waste PET. Reduced carbon dioxide (CO₂) emissions can also contribute to achieving carbon neutrality policies.
Conventional steel fibers corrode due to moisture, making storage in humid environments difficult and ensuring durability challenging when constructing in seawater sections. However, this new technology does not corrode due to moisture, enabling construction even in seawater sections with high moisture and allowing durability to be secured.
DL Construction plans to apply the technology to the Indeogwon–Dongtan Section 10 and the Okjeong–Pocheon Section 2 projects.
A DL Construction official said, "This technology ensures not only quality and economic feasibility but also safety and eco-friendliness," adding, "We will continue to strengthen ESG management through the development of eco-friendly new technologies and build sustainable construction sites."