| 1. |
- Sitnikov, I., et al.
(författare)
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Early structure formation in concrete with water-to-cement ratio 0.2
- 2018
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Ingår i: American Concrete Institute, ACI Special Publication. - : American Concrete Institute.
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Konferensbidrag (refereegranskat)abstract
- Synopsis: Concrete with w/c ratio of 0.2 and lower is indeed material of a new generation. Its properties significantly surpass such of regular concrete grades in large due to the absence of mixing water not actively involved in the physical-chemical processes of cement hydration. In a sense, w/c ratio of 0.2 signifies a threshold in the material science of concrete that no research did reach before 1990s. To move this realm even further, we have been aiming at producing UHPC that crosses this threshold we felt a necessity to define a basic phenomenology of such concrete hardening, especially on the early stages. Our analysis of the kinetics of the strength gain provides that this concrete gains its main physical-mechanical properties after 7 days, and its compressive strength exceeds 100 MPa (14 500 psi) already after 24 hours in normal conditions. At last, this type of UHPC is economically viable due to a relatively low content of cement (500kg/m3 (31.2 pcf)), the use of ordinary fine aggregate, and a possibility of using standard batching equipment in the production.
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| 2. |
- Sitnikov, Vasily, et al.
(författare)
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Kinetics of UHPC strength gain at subfreezing temperatures
- 2018
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Ingår i: American Concrete Institute, ACI Special Publication. - : American Concrete Institute.
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Konferensbidrag (refereegranskat)abstract
- Synopsis: It is well-known that cooling of fresh concrete to a subfreezing temperature interrupts the structure formation and can lead to serious damages of constructions. Most of the existing antifreeze additives reduce this destructive effect, however it should be acknowledged that the processes of cement hydration is still interrupted to an extent that the strength gain in these conditions is simply negligible. When using these admixtures, it is merely expected that concrete will not lose its integrity during the phase of cooling and that strength will be gained after the ambient temperature will reach positive values. However, in our work we aim at proving the possibility of rapid strength gain of UHPC with reduced water-cement ratio even at subfreezing temperatures. The following article presents analysis of the influence of various in-house developed admixtures on kinetics of strength gain of UHPC at negative temperatures.
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| 3. |
- Pontello, Enrico, et al.
(författare)
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Robotically Fabricated Ice Formwork : An Exploration on Casting Morphologically Programmed Complex Concrete Element with Robotically Milled Ice Formworks
- 2019
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Ingår i: International conference. - : KNOWLEDGE E. ; , s. 484-496
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Konferensbidrag (refereegranskat)abstract
- This document focuses on the exploration of casting complex concrete architectural elements with ice formwork. Replacing conventional concrete formwork with ice formwork, allows to produce architectural elements with complex geometries in a highly controlled offsite production process, with almost complete reuse of the mold material. Using digitally driven fabrication tools such as a robotic arm milling, the goal is to achieve 3d shapes made from one or more ice molds, able to be stacked, assembled and merged together in order to define architectural partitions. One of the main instigators of this research is the sustainability, showcased both through the usage of ice as a mold material that is 100% reusable, and the unique ability of the described process to produce topology optimised shapes in concrete, which reduces the use of this high carbon footprint materal to a bare minimum. Ice formwork allows furthermore, to create bespoke shapes for every single element in an efficient way. This opens new avenues for architectural design and construction. This project uses a design based research methodology, where each physical iteration is carefully evaluated against the digital model, embracing morphological material programming.
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| 4. |
- Sitnikov, Vasily
(författare)
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All That Is Porous : Practicing Cross-Disciplinary Design Thinking
- 2020
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Ingår i: Design Transactions. - London : UCL Press. ; , s. 122-127
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Bokkapitel (refereegranskat)abstract
- This chapter discusses the material systems commonly employed in the production of precast concrete elements. In particular, it presents an alternative to expanded polystyrene (EPS), a material that is often used in moulding production for complex-shaped concrete elements. Although EPS plays an important role in the production of an energy-efficient built environment, the ecological implications of its growing global use, and inevitably growing waste, raise serious environmental concerns. Putting the industrial policies of EPS use under question, the author proposes the concept of an alternative ice-based material system for concrete manufacturing. This method provides a waste-free, closed-loop recycling manufacturing process. It enables the production of intricate and formally rich structural formations in concrete, for example mesoscale trabecular concrete structures – spatial material organisations that exceed the scale of concrete microstructures, but are much smaller than the design detailing of the concrete elements. Initially intended to merely eliminate production waste, ice-based concrete manufacturing is a relatively little-explored field in material organisation. This novel opportunity to produce reduced-weight concrete elements with differential local physical properties and expressive formal language is a welcome side-effect of stepping outside standard material practices.
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| 5. |
- Sitnikov, Vasily
(författare)
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Ice Formwork : The Rationale and Potential of Ice-Based Moulding Systems for the Production of Complex-Geometry Precast Concrete
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis analyses and makes proposals about adapting the poten-tial of digital means of production to the needs of the concrete industry. More precisely, it aims at fostering the development of sustainable material cycles and the innovation in manufacturing methods in the field of architectural and structural design of ultra-high performance fibre-reinforced concrete (UHPFRC). The first part of the thesis approaches this intertwined technical problem of digital innovation in the production of concrete with an analysis of the current state of affairs in the concrete industry. As such, this analysis spans from the material science of concrete to life-cycle assessment to archi-tectural and structural design development discourse and computer-aided manufacturing. These analytical cogitations in turn lead to the experimental programme of the second part of the thesis. In the course of these research activities, a non-conventional material system based on robotically-processed ice moulds for non-standard cast concrete parts was found to support a highly economical, sustainable and automated production process, as well as to promote the advancement of concrete design in architecture and structural engineering.The Ice Formwork system is a digital fabrication method proposed, stud-ied and tested in the course of this doctoral research. The method enables production of bespoke design geometry using artificially frozen water as the moulding material in lieu of the petrochemical or engineered wood prod-ucts conventionally used for the moulding. Water replaces the conventional non-recyclable moulding materials and can be continuously reused, forming an optimal closed-loop material flow in the production process.It has been identified that the Ice Formwork method can significantly reduce the embodied energy and carbon footprint of the derivative concrete products and allows reduced cement consumption as it is compatible with UHPC, and that it fully supports the production of complex and mass-op-timized concrete structures. In addition, a unique practical advantage of Ice Formwork is the rapid and autonomous demoulding process facilitated by simple melting of the ice moulds. The method thus allows the robotic fab-rication of design geometry that would be unfeasible with other production methods.The research work has resulted in a fundamental study of the new mate-rial configuration of ice-based concrete production. The technological system has been examined in three scientific areas: the material science of concrete, the robotic mechanical processing of ice with consideration of the challenges posed by architectural design geometry, and the environmental assessment of the proposed system. These disciplinary studies have been published through peer-reviewed sources and are appended to this thesis.
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| 6. |
- Sitnikov, Vasily
(författare)
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Ice Formwork for High-Performance Concrete : A Model of Lean Production for Prefabricated Concrete Industry
- 2019
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Ingår i: STRUCTURES. - : ELSEVIER SCIENCE INC. - 2352-0124. ; 18, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- This article describes an alternative material system for the fabrication of concrete precast elements using ice-based CNC-milled formwork. The use of ice as formwork resolves several systematic problems related to sustainability which are associated with the production of free-form prefabricated concrete elements, including the issue of material waste produced with existing models of fabrication. On the one hand, automation of formwork production by means of CNC machinery allows for the production of complex and precise geometries; on the other hand, as ice naturally melts away once the concrete has structurally set, the manual labor involved in the whole cycle of production is reduced dramatically. The Ice Formwork system is based on the utilization of a frost-resistant design of high-performance concrete (HPCfr). Numerous tests have proven that the Ice Formwork method of casting provides a high quality geometric transfer from ice to concrete, ensuring that no deformation of formwork occurs during the casting process. A key question is whether the trade-off in energy spent on refrigeration to maintain subfreezing temperature throughout the process of fabrication will negate Ice Formworks validity as an alternative to traditional concrete formwork. A preliminary assessment of that question shows that the energy required to produce Ice Formwork won't outweigh the benefits of the proposed fabrication process, enabling a cost efficient and environmentally sustainable solution to casting concrete for a variety of uses.
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| 7. |
- Sitnikov, Vasily
(författare)
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Ice Formwork for Ultra-High Performance Concrete : Simulation of Ice Melting Deformations
- 2017
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Ingår i: Humanizing Digital Reality. - Singapore : Springer, Singapore. - 9789811066108 ; , s. 395-406
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Konferensbidrag (refereegranskat)abstract
- This research project asks how we can efficiently solve structural problems with much smaller masses of concrete while maintaining the same level of cement consumption through the use of Ultra-High Performance Concrete (UHPC), degradable ice formwork, and through an active involvement of digital simulation. A survey undertaken in the recent advancements of concrete-related technologies has revealed an opportunity to propose a new concept of casting. The new method of fabrication for UHPC elements employs ice as the main material of the temporary formwork construction, involves automation of the fabrication process and solves the problems of waste material and manual labour at the demoulding stage. This casting method is being developed for cases in which unique and customized concrete elements of complex geometry are needed, e.g. topology-optimized structural elements. To impose a desirable geometry onto ice, the concept considers the use of 2.5D CNC milling operations. To minimize machining time, milling is thought to be combined with controllable melting of ice that allows achievement of a high-quality surface finish on a large scale in a very simple way. The main hypothesis of the research is that the control over melting could be possible through digital simulation, that is, the melting deformations can be pre-calculated if parameters of the material system are known.
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| 8. |
- Sitnikov, Vasily, et al.
(författare)
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IceFormwork for Cast HPFRC Elements Process-Oriented Design of a Light-Weight High-Performance Fiber-Reinforced Concrete (HPFRC) Rain-Screen Facade
- 2019
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Ingår i: Ubiquity and Autonomy - Paper Proceedings of the 39th Annual Conference of the Association for Computer Aided Design in Architecture, ACADIA 2019. - : ACADIA. ; , s. 616-627, s. 616-627
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Konferensbidrag (refereegranskat)abstract
- The following paper introduces a design implementation of an innovative fabrication method that aims at enabling an environmental and automated production of geometrically challenging cast concrete elements. The fabrication method is based on the use of ice as the molding material for cast concrete. Empirical testing of ice CNC-processing, and a concrete mix capable of hardening at subzero temperatures was undertaken during previous research stages. The current paper illustrates a practical application of ice formwork. A facade rain screen has been developed using algorithmic modeling to illustrate a common case in which a non-repetitive geometrical pattern requires individual formwork to be produced for each element. Existing industrial methods capable of delivering such a project for formidable costs are based on CNC-processed expanded polystyrene (EPS), wood-based materials, or industrial wax formwork. These materials have been found to be either difficult to recycle, expensive, insufficiently strong, energy-or labor-intensive to produce. Preliminary evaluation has shown that ice, used in their place, facilitates a much cleaner, economic, and an even more energy-efficient process. Moreover, a very gentle demolding process through ice-thawing eliminates any shock stresses exposed on newly cast concrete and provides optimal curing conditions. As a result, the thickness of facade elements can be reduced while still fulfilling all structural requirements.
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| 9. |
- Sitnikov, Vasily, et al.
(författare)
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Preliminary Assessment of Environmental Performance of Ice Formwork Production Method for Irregular Architectural Elements of Concrete
- 2024
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Ingår i: International Journal of Space Structures. - : Sage Publications. - 0956-0599.
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Tidskriftsartikel (refereegranskat)abstract
- The present article communicates knowledge in sustainability of a method of digital fabrication in precast concrete production. The method, known as Ice Formwork, serves in production of ultrathin lightweight architectural elements – a novel design typology that has emerged with the development of High-Performance Fibre-Reinforced Concrete (HPFRC). This class of prefabricated concrete structures is expected to reduce cement consumption, adopt digital fabrication processes, and increase design flexibility. In practice however, this production employs suboptimal methods of mould-making, using petrochemical or engineered wood products for single-use moulds. Thus, the excessive amount of non-recyclable waste raises the question of qualities of the advanced digital precast concrete production. The current work builds on the research and development of a novel production method Ice Formwork facilitated through single-use moulds made of artificially frozen water. Previously published work on the subject has covered topics such as cement hydration at subfreezing temperature (Sitnikov and Sitnikov 2018), subtractive digital processing of ice (Sitnikov 2019), and a case of practical application illustrated with the production of a prototype of a lightweight façade rain screen (Sitnikov et al. 2019). Yet, since artificial refrigeration and processing of large amounts of water is essential for Ice Formwork production, the environmental performance of this method requires a thorough examination. Thus, the current piece of work attempts to address two major issues, namely:Energy consumption of industrial refrigeration in production of Ice Formwork.Changes in water mineral content after a cycle of Ice Formwork concrete production.For both topics, the research work required development of an original experimental methodology. This aspect has been given great attention and required development of new technical solutions on many levels. Further research and development is needed to come to a comprehensive environmental assessment, and the results of the current study merely provide a preparatory overview that can help to orient and properly set the objectives for the following research stages.
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| 10. |
- Sitnikov, Vasily, et al.
(författare)
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Preliminary assessment of environmental performance of ice formwork production method for irregular architectural elements of concrete
- 2021
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Ingår i: International Journal of Space Structures. - : SAGE Publications. - 0266-3511 .- 0956-0599 .- 2059-8033. ; 36:1, s. 78-87
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Tidskriftsartikel (refereegranskat)abstract
- The present article communicates knowledge in sustainability of a method of digital fabrication in precast concrete production. The method, known as Ice Formwork, serves in production of ultrathin lightweight architectural elements – a novel design typology that has emerged with the development of High-Performance Fibre-Reinforced Concrete (HPFRC), and helps to reduce cement consumption, adopt digital fabrication processes, and increase design flexibility. In practice, however, this production employs suboptimal methods of mould-making, using petrochemical or engineered wood products for single-use moulds, entailing excessive amounts of non-recyclable waste. The current work builds on the research and development of a novel production method Ice Formwork facilitated through single-use moulds made of artificially frozen water. Previously published work on the subject has covered topics such as cement hydration at subfreezing temperature, subtractive digital processing of ice and a case of practical application illustrated with the production of a prototype of a lightweight façade rain screen. Yet, since artificial refrigeration and processing of large amounts of water is essential for Ice Formwork production, the environmental performance of this method requires a thorough examination. Thus, the current piece of work attempts to address two major issues, namely: (1) Energy consumption of industrial refrigeration in production of Ice Formwork. (2) Changes in water mineral content after a cycle of Ice Formwork concrete production. For both topics, the research work required development of an original experimental methodology. This aspect has been given the great attention and required development of new technical solutions on many levels. Further research and development is needed to come to a comprehensive environmental assessment, and the results of the current study merely provide a preparatory overview that can help to orient and properly set the objectives for the following research stages.
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