TECLA

The soil used for construction was obtained from the site, analysed, and mixed with additives. Using a 3D printing technique, a total of 350 layers consisting of sinusoidal and continuous lines were printed within a time span of 200 hours. After a drying period of approximately 3 months, the structure was fully formed. The load-bearing earth walls eliminate the need for additional framing construction. To ensure effective insulation, the wall cavities were filled with rice husk obtained from agricultural waste.

The foundation is composed of three consecutive layers of rammed earth, rice husks, and gravel. The furniture is integrated into the structure and also printed, with only a few non-printable parts sourced from Italy. In order to improve the printability and structural qualities of raw earth, other materials were mixed in. Since soil composition varies, the mix was enhanced with silica sand, which accounts for 19% of the mixture. Additionally, shredded rice husks were added to increase longevity and help bind the earth mixture on a microscopic level.

However, a significant tradeoff was made, as approximately 10% of the earth mixture by weight consists of binders (4.69% lime and 4.7% hydraulic lime). Binders cannot be considered circular or sustainable, as their production involves the downcycling of stone while emitting high amounts of CO2. Binders only exhibit their binding effect once, during their chemical reaction. In reuse, they lose their binding function and behave like any other grain. Consequently, a new binder is required for each recycling process. Furthermore, binders are produced by quarrying rock or marl, which is pulverised and then burned. Often, high-quality rocks such as limestone are reduced to powder that can only be used once, resulting in relatively low-quality materials with limited durability and strength.

62% of the material used in the project is derived from renewable bio-based sources. Rice husk, the outer shell of rice, is utilised as insulation material for both the building’s envelope and floor. Typically, rice husks are discarded as waste, but in this project, they have been repurposed into a building material, thereby reducing the CO2 footprint associated with rice husks. Normally, rice husks are either burned in fields or left to decompose, contributing to environmental emissions.

With the advancement of modern technology, the automation of labour-intensive processes has become possible, potentially changing the economics of earth structures. WASP, leveraging their experience in small and mid-scale 3D printing, has developed Crane Wasp, a modular printer system with a build area of 50 m2, starting at a price of €132,000. In the construction of Tecla, two printing arms were synchronised to lay each of the 350 12mm lines. Although the printing process took only 200 hours to complete, the earth mixture had to dry for approximately 3 months due to the use of binders.

During this drying period, the printer can be moved and used to print another building, making this technology highly cost-effective. It is conceivable that a set of printers could construct 20 personalised houses, each with its own design, within a year with only a few workers. 3D printing is often regarded as a straightforward way to automate construction processes, but it still requires specialists who can troubleshoot the technology in the event of breakdowns or inconsistent results.