Ice Formwork

The ecological performance of concrete, particularly of its constituent cement, can be endlessly debated, yet there is no alternative material which can compete with its universality and availability. This, however, does not imply that the concrete can´t become a sustainable and environmental material. The ideas of lean production suggest that a performance of a technology can always be improved through a thorough analysis and optimization, e.g. through a careful reformation of the way concrete is treated it should be possible to improve efficiency and durability, reduce its embodied energy and production waste.

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

An illustration of such a decisive optimization can be found in the concept of Ice Formwork - an alternative fabrication approach studied at Royal Institute of Technology in Stockholm by Vasily Sitnikov. While proposing the use of ice as the molding material, this research pursues a development of a completely waste-free and energy efficient application of digital fabrication processes (such as CNC milling) for production of new types of precast concrete construction elements.

The principles of lean production originate from the development of automotive industry that was initially concerned only with efficient management and careful organization of manufacturing process. As more   parameters were being included in the assessment of efficiency, the concept has significantly expanded and now spans over a countless list of aspects associated with economically effective and eco-friendly industrial processes. In principal, the desired performance of production 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 production 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 formwork results in an excessive amount of non-recyclable waste. In addition to environmental issues, the economic performance of this method declines significantly due to inevitably large costs of raw material used for individual mold production.

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 digital production methods. For different reasons the predominant concept today is concrete 3D printing. Popularity of this concept is defined by the absence of any need for centering 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 tolerance of detailing – these are just a few intrinsic characteristics that directly affect the product range of 3D printed concrete.

In response to the above stated issues, a considerable amount of innovative concepts target the production of cast concrete. However, since additive manufacturing has come around, the idea of producing concrete elements in absence of any formwork 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 whatsoever. 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 material 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-performance 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 passes the benchmark of 20 MPa of compressive strength during the first day of hardening at subzero temperature. And since such cold temperatures significantly repels the exothermal reaction, HPCfr works optimally when cast in molds made of ice [2].

There are several unique advantages of Ice Formwork that need to be highlighted. First, the use of ice as formwork material resolves the problem of material waste. As supply of water and electricity are available in any inhabited area, Ice Formwork production can be set up directly on construction site. This option can save a lot of energy usually spent on the transportation of bulk material such as EPS. Moreover, water can be re-used to make ice over and over again, efficiently closing the material loop of production.

Secondly, automated formwork machining by means of CNC milling allows for production of free-form and precise geometries independent of labor. The machining of Ice Formwork is versatile and can be adjusted for a broad range of concrete designs. For instance, ice can serve to merely produce a relief pattern on the cast surface, or several ice parts can be stacked together to make a spatially formed concrete cast.

Finally, as ice naturally melts away once the concrete has harden, the manual labor usually required for demolding is reduced dramatically. Moreover, when using traditional molding systems, a complex geometry of a cast can require additional thickness of the element to reduce risk of braking at demolding. With Ice Formwork demolding is carried out autonomously and gradually due to the slow process of ice melting. And the presence of melt water at this stage eliminates effect of drying shrinkage of young concrete, providing optimal curing conditions.

The high quality of concrete elements produced with Ice Formwork has been illustrated in a set of prototypes presented on an exhibition in September 2018 at the Danish 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 attentive use of materials and digital tools, an efficient, sustainable 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 concrete, but also to break away from the aesthetic image associated with the preceding historical period of modernist precast systems.

Acknowledgements

This project is a part of the InnoChain Research Training Network. It has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 642877. The experimental 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 Sustainability of Concrete Structures. Moscow: American Concrete Institute.

Vasily Sitnikov is an architect and a PhD researcher at the architectural technology department at KTH School of Architecture, Stockholm. After attaining his architecture degree at Moscow State Institute of Architecture, Vasily Sitnikov worked in a private high-performance 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 Städelschule (Staatliche Hochschule für Bildende Künste), Frankfurt am Main. His ongoing PhD research concerns architectural technology, specifically targeting the advancements of technology of precast concrete design and production impelled by the contemporary environmental concerns and the development of digital fabrication.  vasily.sitnikov@arch.kth.se