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Written by: Sara McGillivray
Written on: December 9th, 2011
Tags: building & architecture, material science
Thumbnail by: Luxgineer/Wikimedia Commons
About the Author
Sara McGillivray is a fourth-year student in the USC Bachelor’s of Architecture Program from a very tiny town you’ve never heard of an hour north of USC. When not working in studio, she enjoys exploring Los Angeles and catching up on sleep.
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Volume XIV Issue II > Translucent Concrete: An Emerging Material
Another approach is the “combination of optical fibers and fine concrete”; this formula, explored by the Hungarian Architect Aron Losoncze, uses very fine aggregate to encase optical fibers that allow light to transmit from one side of a block to the other [7]. The process is slow and done by hand in a long, narrow mold; concrete and optical fibers are layered over each other creating a long beam that is cut into blocks [3]. The blocks are able to retain their strength and bond because “the proportion of the fibers is very small (4%) compared to the total volume of the blocks” [7]. They are not reinforced in the traditional sense, since the “optical glass fibres form a matrix” which creates an internal structure of reinforcement [7]. This method of producing translucent concrete has been more fully explored and is more common.

Potential Problems

Concrete mixtures must be just right in order to maintain structural strength. The same is true of translucent concrete. Some experimental translucent concrete mixes have failed to produce structural consistency. In Wittig’s case “lab tests showed that his panels were too fragile to withstand wind and rain” [3]. New construction products must be extensively tested for strength. Traditional unreinforced concrete has a compressive strength of 1000-4000 psi, and a tensile strength of 0 psi; it is reinforced to gain tensile strength [2]. Losoncze’s optical fiber concrete blocks claim a higher compressive strength of 7252 psi and a surprising tensile strength of 1015 psi even without steel reinforcing. His tests show that “glass fibers do not have a negative effect on the well-known high compressive strength value of concrete” [7]. Fiber reinforcing can make translucent concrete even stronger than traditionally reinforced concrete. Engineers can also use chemical additives to significantly increase the strength of translucent concrete [4]. It is possible to create load-bearing structures out of translucent concrete; however it would also be very expensive. It could be about five times as much to build using translucent concrete as opposed to the traditional type [1]. This is due to the rarity of the product and its experimental nature. However, as engineers continue to experiment, the cost of production will decrease, along with with an increase in demand and more widespread usage [4].

Current Production and Uses

Translucent concrete is not currently widely produced. There are only a select few companies, and the process is somewhat low-tech and slow. It can only be produced as pre-cast or prefabricated blocks and panels; it cannot be poured on site like traditional concrete [1, 7]. The blocks come in a range of sizes, the maximum for glass fiber being 1200 x 400 mm (47.2 x 15.7 inches), and the thickness can range from 25-500mm (1-20 inches) [7]. This allows translucent concrete to be used for a variety of purposes, from a thin veneer to a structural system. According to one German company, it can be used “for ventilated facade systems as well as for interior cladding” [8]. So far translucent concrete has been used to make light installations, signs, and fixed-in-place furniture such as benches, desks, and counters. In its early days, it was used mostly in art installations (see Figure 2) and material demonstrations such as the Liquid Stone exhibit at the National Building Museum [5], and a sidewalk in Stockholm that looked “like an ordinary sidewalk by day but [was] illuminated at night by lights under it” [4]. It is presently used mostly in interiors as decoration, but is making its foray into exterior structural walls.