Translucent Concrete or Light-transmitting concrete is an innovative façade material, extensively used to clad interior surfaces and design products with an edge of elegance. It is a concrete-based building material with embedded Nano-optic elements, that create a light-transmissive surface. This property is attained by the uniform distribution of high numerical aperture Plastic Optical Fibers throughout the concrete mass, which support the smooth conduction of light from one end of the block to the other. The result is a rather interesting surface that intrigues its beholders with a graceful play of light and silhouettes.
Although recently popularized, the first mention of translucent concrete has been spotted in a Canadian patent dating back to 1935. With the advancement of innovations in glass and polymer-based optical fibres, the production of translucent concrete began to surface the markets in the 1990s. The material was officially patented in 2001 by the Hungarian architect Áron Losonczi, which is a traditional mix of water, sand, gravel, and cement, embedded with plastic or quartz fibres throughout its mass. Within 2 years of proposing the idea, Losonczi was able to produce the first block of LiTraCon or Light Transmitting Concrete, which was quickly adopted in countries like Italy, Germany, and China.
Constituents of the Material
The material is made up of two major components, fine concrete, and nano optic fibres. In correspondence with concrete’s rudiments, cement, aggregate, and water create the base of the material. Cement, preferably Portland cement, is the binder that sets and hardens over a definite period, and thereby imparts form to the product. Coarse aggregate such as crushed granite or hard basalt chips strengthens the material. Translucent concrete generally does not contain coarse aggregates as they damage the fibers and restrict the passage of light through the concrete block. Fine aggregates, although chemically inactive, also influences the strength of the material as it fills the voids created and reduces porosity. Sand is a commonly used fine aggregate. The water used must be free from acids, alkalis, oils, and other organic impurities. Fast setting cement is preferred for the mix, and craft clay is additionally added as a base for the optical fibres to merge with the concrete.
Optical fibers form the second most crucial component of the material, which further contains three major elements. The core is the thin glass center of the fiber through which the transmission of light occurs. An outer optical material or cladding surrounds the core and deviates the reflected light back into the core. Above this is a plastic buffer coating that protects the fiber from external damage. Some other types of fibers used include Multimode Fibre, Single-mode Fibre, Multimode Step-Index Fibre, Multimode graded-index Fibres, and so on. Superplasticizers such as Neoplast, Glenium, Polyplast SP HPC, etc are also added into the mix. Industrial waste glass, which is hammered and crushed into small pieces, is added to the material in order to increase refractivity.
The process of manufacturing translucent concrete is very similar to that of traditional concrete, with an additional introduction of 4% – 5% optical fibers into the blend. The fibers and small layers of concrete are added alternatively into the mold at intervals of 2mm to 5mm. The thinner and smaller the layer more is the light allowed to pass through. A rectangular mold of steel or wood is prepared into which clay or mud is placed along the sides for easily demolding the exposed optical fibers, that are cut in such a way that they can be placed perfectly inside the mold. The fibers are placed layer-wise and holes are driven on the steel or wooden plate to allow those fibers to pass through. The concrete mixture is then cautiously poured so that no disturbance is created to the optical fibers beneath while vibrating tables are used to avoid the accumulation of voids. The mold and the mud are removed after 24 hours and the excess length of the fibers is cut to the same size as the thickness of the pane. As this is a form of pre-cast concrete, the material is finally cut into blocks or panels, polished to finishes ranging from semi-gloss to high-gloss, and sent for use.
Translucent concrete can be applied to the interior as well as exterior walls. A greater intensity of light results when the sun’s rays hit the concrete at a lower angle, and therefore generates a shiny appearance during sunset while appearing as a regular concrete block during the day. It can be used as load-bearing walls, pavement blocks, partition walls, manufacturing furniture, and decorative fixtures. Its great light-guiding properties can be utilized to increase safety by illuminating speed breakers on highways at night, in aircraft or buildings to guide people towards emergency exits, or to even light up dark public places, such as subway stations.
Although the use of translucent concrete is not widespread yet, its application has been notable in some astounding structures, generally as a façade material. The “European Gate” is one of the most popular landmarks in Hungary due to its light-transmitting quality created by this material. The monument was built in 2004 to celebrate Hungary’s joining the European Union. The Stuttgart City Library in Germany by Yi Architects is another excellent example. Its cube shape combined with a translucent roof allows natural light to illuminate the area, creating an exceptional dynamic interior.
Pros and Cons
Since Translucent concrete allows sufficient passage of light through it, it tends to reduce power consumption, making it an eco-friendly alternative to traditional concrete. It has low thermal conductivity and density, reduces the dead weight on the building, and has a lower handling cost. Other than these economic and environmental advantages, its striking appearance enhances the visual quality and aesthetic appeal of the structure. Experts predict that this high-performance concrete can bring about a positive change in the overall market in the future.
Despite the various advantages of the material, there are a few drawbacks to its usage, especially in large-scale projects. The production of translucent concrete is expensive compared to traditional concrete due to the higher cost of optical fibers. Therefore, for translucent concrete to become a sustainable alternative, it is crucial to find cost-effective ways of manufacturing it. The infusion of optical fibers into the concrete layers requires skilled labor, but most people tend to lack the expertise and the required technology in this area. Translucent concrete is weakened due to the infused nano-optics and cannot be used for columns or beams. Material handling could be hazardous due to the excessive use of glass pieces. The material could also be considered ineffective on surfaces where the sun’s rays do not fall and from an inspection point of view.
Due to the expensive nature of Translucent concrete, it might take several years for its extensive use in the construction industry. This resulted in a surge of manufacturers who are now working towards the development of an affordable alternative of the material for both commercial and residential projects. Several companies have begun to produce translucent concrete using a wide range of production systems. Florak Bauunternehmung GmbH (Heinsberg, Germany), LBM EFO (Berching, Germany), LiTraCon Bt (Csongrád, Hungary), LUCEM GmbH (Aachen, Germany), Luccon Lichtbeton GmbH (Klaus/Austria), LiCrete by Gravelli (Czech Republic) are a few companies that are working towards creating inexpensive translucent concrete products by the introduction of licensing and large-scale production. The widespread use of this eco-friendly concrete would gradually witness lower power consumption, leading to climate betterment as more natural light would be utilized. A stark improvement in health conditions would also be visible since a large population is currently deficient in Vitamin D due to the lack of sunlight that results in reduced bone strength. In conclusion, Translucent Concrete is one of the most innovative elements to diversify the future of building materials.
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