Robert J. Flatt

Last Name

Flatt

First Name

Robert J.

ORCID

0000-0002-5609-8487

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03891 - Flatt, Robert J. / Flatt, Robert J.

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Publications1 - 10 of 102

Sustainable Digital Concrete: Myth, Reality or Emerging Opportunity?
Wangler, Timothy; Patankar, Yamini; Flatt, Robert J. (2024)
Architectural Design
Unbelievably huge amounts of concrete, a major contributor to our contemporary world, are produced every year, and this continues to increase exponentially. ETH Zurich researchers Timothy Wangler, Yamini Patankar and Robert J Flatt explain the pros and cons of the digital fabrication of concrete, and the research still to be done in this relatively young and experimental subset of the construction industry and material science.
Revisiting Folded Forms with Digital Fabrication
Szabo, Anna; Lloret-Fritschi, Ena; Reiter, Lex; et al. (2019)
eCAADeSIGraDi ~ eCAADe SIGraDi 2019. Architecture in the Age of the 4th Industrial Revolution
Early-age hydration of accelerated low-carbon cements for digital fabrication
Das, Arnesh; Wenger, Cedric; Walpen, Lukas; et al. (2025)
Cement and Concrete Composites
Digital fabrication processes with concrete offer several advantages compared to conventional processes, however, a major criticism with related concrete mixes has been with regard to their high cement paste content and consequent carbon footprint. One of the ways to address this is to reduce ordinary Portland cement (OPC) content in such mixes by using supplementary cementitious materials. This paper reports on such an approach for two different digital fabrication methods: digital casting system and 3D concrete printing. Results focus on the combined use of such low carbon blends with a calcium aluminate cement (CAC) based accelerator. Two such accelerators were studied: one being mainly crystalline based and the other mainly amorphous. Their performance is assessed at different temperatures. It is concluded that crystalline CAC is more suitable for applications above 20 °C while at temperature below 20 °C, amorphous CAC should be preferred. This paper also delves deeper into the effect of amorphous CAC on the hydration of tricalcium silicate present in OPC. It shows that the effect of amorphous CAC on that silicate depends on the OPC content of the system as well as on the type and amount of calcium sulfate used in the accelerator formulation.
Eggshell Pavilion: a reinforced concrete structure fabricated using robotically 3D printed formwork
Burger, Joris Jan; Aejmelaeus-Lindström, Petrus; Gürel, Seyma; et al. (2023)
Construction Robotics
This paper discusses the design, fabrication, and assembly of the ‘Eggshell Pavilion’, a reinforced concrete structure fabricated using 3D printed thin shell formwork. Formworks for columns and slabs were printed from recycled plastic using a pellet extruder mounted to a robotic arm. The formworks were cast and demoulded, and the finished elements were assembled into a pavilion, showcasing the architectural potential of 3D printed formwork. The Eggshell Pavilion was designed and fabricated within the scope of a design studio at ETH Zurich. The structure was designed using a fully parametric design workflow that allowed for incorporating changes into the design until the fabrication. The pavilion consists of four columns and floor slabs. Each column and floor slab is reinforced with conventional reinforcing bars. Two different methods are used for casting the columns and floor slabs. The columns are cast using ‘Digital casting systems’, a method for the digitally controlled casting of fast-hardening concrete. Digital casting reduces the hydrostatic pressure exerted on the formwork to a minimum, thereby enabling the casting of tall structures with thin formwork. The floor slabs are cast with a commercially available concrete mix, as the pressure exerted on the formwork walls is lower than for the columns. In this research, 3D printed formwork is combined with traditional reinforcing, casting, and assembly methods, bringing the technology closer to an industrial application.
Do superplasticizers work the way we think? New insights from their effect on the percolation threshold of limestone pastes
Sha, Shengnan; Mantellato, Sara; Weckwerth, Stefanie Anne; et al. (2023)
Cement and Concrete Research
Superplasticizers are polymeric dispersants that play a major role in concrete technology. Despite their ubiquity and much research on their working mechanisms, many questions remain about the effects of their molecular structures on their working mechanism, in particular their ability to lower the yield stress of particulate suspensions. It is generally recognized that superplasticizers decrease attractive interparticle forces, thereby reducing or eliminating yield stress. It is also often assumed that changes in yield stress should be proportional to changes in interparticle forces. This paper takes a fresh look at this question, revisiting Yodel (YD) and modified shifting factor (MSF) models that not only incorporate interparticle forces, but also percolation thresholds. This leads us to conclude that a major impact of superplasticizers is to modify the percolation threshold in direct relation to their adsorption.
A 3D Model with Extended Reality of Lausanne Cathedral
Varga, Matej; Patankar, Yamini; Grossenbacher, Nando; et al. (2024)
SIG 2024 - Proceedings of the International Symposium on Engineering Geodesy
The field of 3D modeling, encompassing both geometry and texture information, has been rapidly advancing, particularly with the integration of semantic information, extended reality (XR), and Building Information Modeling (BIM) capabilities. These content-rich digital models expand the scope of applications in various fields, including virtual tours, digital reconstruction, and heritage preservation. Traditionally, data collection has been a core task of geomatics, but efficient data processing, modeling, and visualization require interdisciplinary expertise. This paper presents a workflow detailing all steps from data planning and collection to the creation of a 3D model enriched with virtual capabilities, using the Lausanne Cathedral in Switzerland as a case study. Data collection was performed using terrestrial, handheld, and mobile laser scanners and RGB cameras. We discuss our decisions to ensure high-quality data collection, addressing variables such as overlap, challenging environments, and noise control. We detail the steps to reconstitute the cathedral's geometry, including registration, noise cleaning, subsampling, and addressing bottlenecks at each stage. Finally, we describe the development of VR experiences for various cathedral spaces, presenting selected case examples.
Heritage ++, a Spatial Computing approach to Heritage Conservation
Patankar, Yamini; Tennenini, Camilla; Bischof, Rafael; et al. (2024)
RILEM Technical Letters
Historic structures are affected by numerous degradation processes driven by a complex system of interconnected and mutually influencing factors. Preserving these monuments is a multidisciplinary endeavour that extends beyond one-time interventions, necessitating a comprehensive methodology that involves various stakeholders, expert consultations, monitoring tools, and impact assessments. Limitations arise due to communication barriers and difficulty in translating and transferring experience among disciplines, often compromising the collective ability to define the best possible conservation strategies.Recent advancements in 3D modelling and data management technologies offer collaborative platforms for information sharing. However, the complex interfaces of these tools often limit their accessibility, making them exclusive to specialists. Integrating Spatial Computing could address these challenges by fostering intuitive engagement and enhancing accessibility and depth in interdisciplinary interactions. This letter outlines initial efforts in using spatial computing to tackle the challenges of built heritage conservation and presents a vision for its future development.
Statistical Analysis at the Service of Conservation Practice: DOE for the Optimisation of Stone Consolidation Procedures
Praticò, Ylenia; Caruso, Francesco; Wangler, Timothy; et al. (2016)
Science and Art: A Future for Stone. Proceedings of the 13th International Congress on the Deterioration and Conservation of Stone
Ethyl silicates are extensively used in the field of conservation to treat various types of stones. It is common belief that the different conditions of temperature, humidity and techniques of application influence the resulting consolidation. In this study, a statistical Design of Experiments (DOE), that allows the exploration of the simultaneous effect of different factors in a limited number of experiments, is used to study this. It is applied to analyse the possible crossed effect of temperature, relative humidity, application procedure, concentration and pre-treatment with a swelling inhibitor on the consolidation of a swelling clay-bearing sandstone. The purpose is to obtain an optimization of the consolidation treatment under conditions that are both reliable in the laboratory and on site. The results obtained with our approach show that the consolidation is not affected by temperature, humidity or the application method. On the other hand, the curing time is strongly influenced by the above-mentioned factors. In particular, it is shown that higher initial moisture content is beneficial to the consolidation treatment as it significantly shortens the curing time.
Adapting Smart Dynamic Casting to Thin Folded Geometries
Szabo, Anna; Reiter, Lex; Lloret-Fritschi, Ena; et al. (2018)
RILEM Bookseries ~ First RILEM International Conference on Concrete and Digital Fabrication – Digital Concrete 2018
Understanding hydration reactions, mechanical properties, thermal expansion, and organic interfacial interactions of calcium sulfate hydrates from the atomic scale
Mishra, Ratan Kishore; Darouich, Samir; in 't Veld, Pieter J.; et al. (2025)
Cement and Concrete Research
Calcium sulfates such as anhydrite, hemihydrate, and gypsum are used extensively in building materials, wall board, and biomaterials. The correlation between nanoscale structure and macroscopic properties, however, remains incompletely understood. We employed molecular dynamics simulations with the Interface Force Field (IFF) to examine sensitive hydration reactions, anisotropic thermal and mechanical properties, as well as (hkl) specific adsorption of organic modifiers. Computed thermal transitions between calcium sulfate phases, directional coefficients of thermal expansion, and directional mechanical properties agree exceptionally well with partially known experimental measurements, provide missing data and mechanistic understanding at the atomic scale. Polymeric naphthalene sulfonate-formaldehyde condensates exhibit strong, selective adsorption to the hemihydrate (001) surface. The polymer conformations and facet-specific binding affinities explain the delayed hydration of calcium sulfate hemihydrate to gypsum. The simulation methods can be applied to predict crystal growth and properties of sulfate-containing multiphase materials from atoms to the micrometer scale.

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Robert J. Flatt

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