A recent review published in the journal Buildings has spotlighted optical fiber light-transmitting concrete (LTC), a material that allows light to pass through concrete. Known for its aesthetic appeal and innovative functionality, LTC shows great potential for use in sustainable and energy-efficient construction projects.
Study: Development of Optical Fiber Light-Transmitting Concrete (LTC)—A Review. Image Credit: CoreDESIGN/Shutterstock.com
Materials and Fabrication Methods
LTC relies on optical fibers—typically made from glass or polymethylmethacrylate (PMMA)—to channel light through its structure. While both materials offer over 90% light transmission, PMMA is preferred due to its affordability, robustness, and ease of application in construction. However, the high alkalinity of conventional silicate cement can degrade these fibers. To address this, researchers recommend using alumina sulfate cement, which is less alkaline and offers high early strength, making it better suited for LTC applications.
The fabrication of LTC typically follows one of three methods:
- First-implantation: Optical fibers are placed in a mold, secured, and surrounded with fine-grained concrete, cement, and mortar. After curing, the product is cut to the desired strength.
- Post-implantation: Concrete is poured first, and fibers are inserted into pre-drilled holes after curing.
- Paving: Layers of optical fiber panels and concrete mix are alternated in a mold until the structure is complete.
Each approach has its advantages, and the choice depends on specific project requirements.
Light Transmission and Structural Benefits
LTC’s ability to transmit light is its defining feature, but the performance depends on several variables, including the diameter, spacing, and quantity of fibers. Generally, increasing fiber content improves transmittance, but larger diameters or rough fiber ends can scatter light, reducing efficiency.
Beyond aesthetics, LTC also offers improved mechanical properties compared to traditional concrete. Its flexibility and ductility are enhanced by the inclusion of optical fibers, which also boost bending strength. However, LTC’s increased porosity—caused by the fiber incorporation—makes it more water-absorbent than plain concrete.
The material’s unique combination of functionality and visual appeal has attracted significant interest from architects. Since its first major application in the Franco Church in 2004, LTC has been used in various designs, including exterior walls, interior partitions, and decorative panels. Companies like Italcementi Group, Luccon, and Litracon have commercialized LTC products, creating wall panels, ceilings, stairs, and even translucent pavements, such as Sapphire Corporation Ltd.’s 2019 display at the World Park.
Economic and Environmental Considerations
The cost of optical fibers remains a barrier to wider LTC adoption. Compared to materials like glass or resin, fibers are expensive, and their installation is labor-intensive, further driving up costs. Moreover, while production costs increase with fiber volume, higher fiber content doesn’t always equate to better light transmission.
Despite these challenges, LTC offers significant energy-saving potential. Studies show that a wall with 5 % transmittance can reduce artificial lighting needs by 16 %. Additionally, LTC with 5.6 % fiber content has been found to lower energy consumption for heating and cooling by 18 %, making it a compelling option for reducing carbon emissions in buildings.
Future Directions
LTC is steadily gaining recognition as a versatile material that blends practicality with design. However, to expand its applications, researchers must address challenges such as long-term durability and high production costs. Automating the fiber-placement process could make manufacturing more efficient and cost-effective, while exploring alternative materials like resin might also lower expenses.
Further research into the relationship between LTC’s mechanical properties and light transmission could open doors to new uses, such as in infrastructure projects like roads and tunnels. In these settings, LTC’s ability to transmit light could support structural health monitoring and improve safety.
With continued advancements, LTC has the potential to move beyond its current niche, becoming a key player in innovative and sustainable construction.
Journal Reference
Bai, J., Zhang, W., Tian, J., Wu, X., & Zheng, M. (2024). Development of Optical Fiber Light-Transmitting Concrete (LTC)—A Review. Buildings, 15(1), 104. DOI: 10.3390/buildings15010104, https://www.mdpi.com/2075-5309/15/1/104
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