Sara Mantellato

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Mantellato

First Name

Sara

ORCID

0000-0003-3941-0739

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Publications 1 - 8 of 8

Additive Digital Casting: From Lab to Industry
Lloret-Fritschi, Ena; Quadranti, Elia; Scotto, Fabio; et al. (2022)
Materials
Concrete construction harms our environment, making it urgent to develop new methods for building with less materials. Structurally efficient shapes are, however, often expensive to pro- duce, because they require non-standard formworks, thus, standard structures, which use more material than is often needed, remain cheaper. Digital fabrication has the potential to change this paradigm. One method is Digital Casting Systems (DCS), where the hydration of self-compacting concrete is controlled on the fly during production, shortening the required setting time and reduc- ing hydrostatic pressure on the formwork to a minimum. This enables a productivity increase for standard concrete production. More importantly, though, it enables a rethinking of formworks, as the process requires only cheap thin formworks, thus, unlocking the possibility to produce opti- mised structural members with less bulk material and lower environmental cost. While DCS has already proven effective in building structural members, this process faces the challenge of moving into industry. This paper covers the next steps in doing so. First, we present the benchmark and expectations set by the industry. Second, we consider how we comply with these requirements and convert our fast-setting self-compacting mortar mix into a coarser one. Third, we present the next generation of our digital processing system, which moves closer to the industrial requirements in terms of size and the control system. Finally, two prototypes demonstrate how DSC: (a) increases standard bulk production by 50% and (b) can be cast into ultra-thin formworks. We discuss the results and the short-term industrial concerns for efficiency and robustness, which must be ad- dressed for such a system to be fully implemented in industry.
Effect of processing on the air void system of 3D printed concrete
Das, Arnesh; Song, Yu; Mantellato, Sara; et al. (2022)
Cement and Concrete Research
The long-term performance of 3D printed concrete structures involves various durability issues, and in this study, we are focusing on frost damage. This can be a serious issue in cold places like Switzerland and may be particularly problematic for 3D printed structures owing to the likely presence of cold joints. 3D printing often involves processing steps such as pumping, set acceleration and extrusion, and in the present work, we consider the effect of these processing conditions on the air void system. It was found that pumping and extrusion processes significantly change the void structure while acceleration or higher setting rates can stabilize them, the latter ensuring a higher protection from frost damage. It was also seen that after extrusion, cast and printed samples have very comparable void systems and spatial distribution of voids, implying no clear impact of the presence of interfaces in the
Influence of pumping/extrusion on the air-void system of 3D printed concrete
Das, Arnesh; Song, Yu; Mantellato, Sara; et al. (2020)
RILEM Bookseries ~ Second RILEM International Conference on Concrete and Digital Fabrication. Digital Concrete 2020
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.
Early-age rheology and hydration control of ternary binders for 3D printing applications
Das, Arnesh; Reiter, Lex; Mantellato, Sara; et al. (2022)
Cement and Concrete Research
Achieving and controlling the desired strength build-up is important for 3D concrete printing. In this paper, we investigate the possibility of using calcium aluminate cement (CAC) as an accelerator for Ordinary Portland Cement (OPC) for 3D extrusion printing. Both ternary and binary cement systems were studied whereby for the former, the third component was a calcium sulfate source (C\$). Experiments are conducted on mixes both in presence and absence of retarders. They focus on hydration progress, evolution of rheological properties and microstructural development. It is concluded that CAC-C\$ can be effectively used as an accelerator to achieve the desired rates of strength build-up. Additionally, it is shown that strength build-up has is directly related to CAC dosage, irrespective of the presence of retarders. Based on microstructure characterization results, AFt and AH3 are found to be formed in the first hour after acceleration and responsible for the observed strength build-up.
Eco-Friendly, Set-on-Demand Digital Concrete
Boscaro, Federica; Quadranti, Elia; Wangler, Timothy; et al. (2022)
3D Printing and Additive Manufacturing
Digital fabrication with concrete is considered to potentially revolutionize the construction sector and is often presented as a means to reduce its environmental footprint. However, at least in the case of concrete, it encounters significant challenges in terms of material design, since high paste volumes and Portland cement contents are normally used due to process requirements. In this article, the application to layered extrusion of a recently developed low clinker cement containing 50% Portland cement and 50% supplementary cementitious materials, such as limestone, burnt oil shale, and fly ash, is presented. It is found that an accelerator paste composed by Calcium Aluminate Cement (CAC) and anhydrite provides the required hydration and structural build-up for 3D printing, while not compromising the early and long-term compressive strength. Such a low clinker mortar can be successfully retarded, processed, pumped, and extruded just after mixing it in line with the accelerator paste. This accelerated mortar formulation contains only 303 kg/m(3) of Portland cement, which is roughly half the amount used in current accelerated formulations used for digital fabrication with concrete.
Shifting factor-A new paradigm for studying the rheology of cementitious suspensions
Mantellato, Sara; Flatt, Robert J. (2020)
Journal of the American Ceramic Society
Blended calcium aluminate cements for digital fabrication with concrete
Das, Arnesh; Reiter, Lex; Mantellato, Sara; et al. (2022)

Publications 1 - 8 of 8

Sara Mantellato

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