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CONCRETE TECHNOLOGY

Lean Technology for Precast Production

Ice

˾ Vasily Sitnikov, MA, PhD Candidate, KTH School of Architecture, Stockholm

The ecological performance of concrete, particularly of its approach studied at Royal Institute of Technology in Stock- constituent , can be endlessly debated, yet there is holm by Vasily Sitnikov. While proposing the use of ice as no alternative material which can compete with its univer- the molding material, this research pursues a development sality and availability. This, however, does not imply that of a completely waste-free and energy efficient application the concrete can´t become a sustainable and environmen- of digital fabrication processes (such as CNC milling) for tal material. The ideas of lean production suggest that a production of new types of construction performance of a technology can always be improved elements. through a thorough analysis and optimization, e.g. through a careful reformation of the way concrete is treated it The principles of lean production originate from the develop- should be possible to improve efficiency and durability, ment of automotive industry that was initially concerned only reduce its embodied energy and production waste. An with efficient management and careful organization of man- illustration of such a decisive optimization can be found in ufacturing process. As more parameters were being included the concept of Ice Formwork – an alternative fabrication in the assessment of efficiency, the concept has significantly expanded and now spans over a countless list of aspects as- sociated with economically effective and eco-friendly indus- trial processes. In principal, the desired performance of pro- duction is thought to be achieved through thoughtful use of labor, material and energy. However, compliance with these principles in the construction industry is often excessively challenging. For example, the production of non-standard concrete elements according to the principle of lean produc- tion has not been resolved until now. In most cases such a production is realized through use of expanded polystyrene (EPS) formwork. EPS blocks are CNC milled and coated with protective layer of epoxy resin or poyurea in order to produce complex and accurate shapes. Given that such molds are not intended for serial production, the use of this type of form- work results in an excessive amount of non-recyclable waste. In addition to environmental issues, the economic perfor- mance of this method declines significantly due to inevitably large costs of raw material used for individual mold produc- tion.

In order to propose an effective solution to the problem stated above, a lot of research has been dedicated to analysis, experimentation, and development of various alternative dig- ital production methods. For different reasons the predomi- nant concept today is concrete 3D printing. Popularity of this concept is defined by the absence of any need for centering

Fig. 1: Concrete cladding element produced fr

Photograph: Anders Photograph: Ingvartsen with two-component Ice Formwork and HPC .

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CONCRETE TECHNOLOGY CONCRETE ˾ Vasily Sitnikov is an architect and a PhD researcher at the architectural technology depart- ment at KTH School of Architecture, Stockholm. After attaining his architecture degree at PLANT Moscow State Institute of Architecture, Vasily Sitnikov worked in a private high-performance INTERNATIONAL concrete laboratory in Moscow, where he has developed his knowledge in material science. In 2014 Vasily Sitnikov has received a postgraduate degree in art and architecture at Städel- schule (Staatliche Hochschule für Bildende Künste), Frankfurt am Main. His ongoing PhD re- search concerns architectural technology, specifically targeting the advancements of technology of precast concrete design and production impelled by the contemporary environmental concerns and the develop- ment of digital fabrication. [email protected] Our free eService:

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Photograph: Anders Ingvartsen

Fig. 2: Relief panels produced with the Ice Formwork method, 400 mm * 200 mm, HPCfr concrete. ICCX newsletter

or formwork, coupled with a wide range of geometries it can be used for. However, there are several substantial issues related to the nature of 3D printed concrete that substantially narrow down the field of applications for additive manufacturing. Cold joints between deposited layers, cumbersome reinforcement techniques, low tol- Interested? erance of detailing – these are just a few intrinsic characteristics that directly affect the product range of 3D printed concrete. Register here: www.cpi-worldwide.com/registration In response to the above stated issues, a considerable amount of innovative con- cepts target the production of cast concrete. However, since additive manufacturing has come around, the idea of producing concrete elements in absence of any form- work has raised the bar of production performance. Today, to make a competition with the additive fabrication one has to propose a system of production automation of cast concrete elements of arbitrary geometry without any material waste what- soever. A potential solution to this challenge is to use ice as the molding material, a concept called Ice Formwork [1]. Essentially, Ice Formwork is an alternative mate- rial base for fabrication of precast concrete elements that employs CNC-milled ice molds. The core of the concept is the composition of frost-resistant high-perfor- mance concrete (HPCfr) developed in the course of this research. HPCfr is capable of gaining the compressive strengths over 120 MPa on the 28th day even when the initial concrete mix temperature is -10°C (minus ten degrees Celsius). Even though the low temperature inevitably slows down the strength gain of fresh concrete, HPCfr

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CONCRETE TECHNOLOGY Photograph: Anders Photograph: Ingvartsen

Fig. 3: A cast concrete element after demolding is kept in melt water to facilitate curation process.

passes the benchmark of 20 MPa of compressive strength versatile and can be adjusted for a broad range of concrete during the first day of hardening at subzero temperature. And designs. For instance, ice can serve to merely produce a relief since such cold temperatures significantly repels the exother- pattern on the cast surface, or several ice parts can be stacked mal reaction, HPCfr works optimally when cast in molds made together to make a spatially formed concrete cast. of ice [2]. Finally, as ice naturally melts away once the concrete has There are several unique advantages of Ice Formwork that harden, the manual labor usually required for demolding is need to be highlighted. First, the use of ice as formwork ma- reduced dramatically. Moreover, when using traditional mold- terial resolves the problem of material waste. As supply of ing systems, a complex geometry of a cast can require addi- water and electricity are available in any inhabited area, Ice tional thickness of the element to reduce risk of braking at de- Formwork production can be set up directly on construction molding. With Ice Formwork demolding is carried out au- site. This option can save a lot of energy usually spent on the tonomously and gradually due to the slow process of ice melt- transportation of bulk material such as EPS. Moreover, water ing. And the presence of melt water at this stage eliminates can be re-used to make ice over and over again, efficiently effect of drying shrinkage of young concrete, providing opti- closing the material loop of production. mal curing conditions.

Secondly, automated formwork machining by means of CNC The high quality of concrete elements produced with Ice milling allows for production of free-form and precise geome- Formwork has been illustrated in a set of prototypes pre- tries independent of labor. The machining of Ice Formwork is sented on an exhibition in September 2018 at the Danish

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CONCRETE TECHNOLOGY

Royal Academy of Arts. Multiple tests demonstrated the high quality of both the concrete structure and the surface quality, illustrating the variety of geometrical shapes that can be made with the Ice Formwork production method.

Only through challenging the conventional thinking and at- tentive use of materials and digital tools, an efficient, sustain- able and expressive architecture will make its way into our daily life. By optimizing the amount of cement for structural elements, and by following the standards of lean production it is not only possible to improve environmental profile of con- crete, but also to break away from the aesthetic image asso- ciated with the preceding historical period of modernist pre- cast systems.

Acknowledgements

This project is a part of the InnoChain Research Training Net- work. It has received funding from the European Union's Hori- zon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 642877. The experi- mental part of the work has been financially supported by the National Real Estate Board of Sweden (Statens Fastighetsverk) through Helgostipendier 2017 and Helge Ax:son Johnsons Foundation 2018. ˾

References

[1] Sitnikov, Vasily. 2019. “Ice Formwork for High-Performance Concrete: A Model of Lean Production for Prefabricated Concrete Industry.” Structures (In Press). [2] Sitnikov, Vasily, and Ivan Sitnikov. 2018. “Kinetics of UHPC Strength Gain at Subfreezing Temperatures.” In SP-326 Durability and Sustain- ability of Concrete Structures. Moscow: American Concrete Institute.

FURTHER INFORMATION

www.iceformwork.com www.instagram.com/iceformwork

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