TRC SANDWICH SOLUTION FOR ENERGY RETROFITTING

Concerning energy improvement of existing façades, a favourable system involves prefabricated multilayer panels, made of internal insulation core and outer textile reinforced concrete layers. It is a convincing alternative to external thermal insulation composite systems (ETICS) and ventilated façades, and it meets all the requirements for façade systems. The main advantage is the possibility to apply the panel using a crane, without any scaffolding. The paper considers two solutions: the former uses expanded polystyrene (EPS) as insulating material; the latter substitutes EPS with an innovative green insulation material made of inorganic diatomite. The paper aims at comparing the solutions in terms of mechanical properties of the components and behaviour of the composite sandwich at lab-scale level. Numerical models, previously calibrated, will be instrumental for the discussion

TRC sandwich solution for energy retrofitting

Concerning energy improvement of existing façades, a favourable system involves prefabricated multilayer panels, made of internal insulation core and outer textile reinforced concrete layers. It is a convincing alternative to external thermal insulation composite systems (ETICS) and ventilated façades, and it meets all the requirements for façade systems. The main advantage is the possibility toapply the panel using a crane, without any scaffolding. The paper considers two solutions: the former uses expanded polystyrene (EPS) as insulating material; the latter substitutes EPS with an innovative green insulation material made of inorganic diatomite. The paper aims at comparing the solutions in terms of mechanical properties of the components and behaviour of the composite sandwich at lab-scale level. Numerical models, previously calibrated, will be instrumental for the discussion

REVISIONE DEI MODELLI NUMERICI ALLA MACROSCALA PER LO STUDIO DEL FENOMENO DI INFRAGILIMENTO DA IDROGENO

Il fenomeno di infragilimento da idrogeno, noto da diversi anni, rimane un argomento di grande interesse scientifico. Di recente, in letteratura l’attenzione si è spostata prevalentemente sullo sviluppo di modelli numerici in grado di riprodurre il fenomeno o di chiarire e/o interpretare alcuni aspetti che lo caratterizzano. Diverse sono le scale dimensionali considerate: scala atomistica, nano, meso, macroscala. I modelli sviluppati alla macroscala sono prevalentemente modelli ad elementi finiti di tipo coesivo il cui scopo è la valutazione della resistenza meccanica di un materiale sotto effetto combinato di sollecitazione meccanica applicata e ambiente aggressivo, in particolare ricco di idrogeno atomico. Il presente lavoro propone una revisione dei modelli numerici alla macroscala presenti in letteratura al fine di riassumere lo stato dell’arte, di valutare pro e contro dei modelli presenti e individuare quali possano essere gli sviluppi futuri per l’ottimizzazione di un approccio numerico a questa scala

Porous Geopolymer Components

Geopolymers are based on an inorganic 3D network of alumino-silicate units usually synthesized through reaction of alumino-silicate powders in presence of a silicate alkaline solution. The rheological characteristics of the reactive mixtures and the fact that these systems can consolidate at low or even room temperature, together with their intrinsic micro- and meso-porosity and mechanical properties, are the reason why they are considered for a wide range of applications, such as construction materials, thermal insulation, filters, adsorbers and so on. Open cell alkali or acid-based geopolymer foams were produced by direct foaming using different fabrication approaches. Potassium-based foams with a porosity up to 85 vol% were obtained from metakaolin, potassium silicate and potassium hydroxide, while metakaolin and phosphoric acid were used to fabricate foams containing an aluminum phosphate crystal phase already after synthesis at room temperature, and a total porosity of ~80 vol%. The strength of the foams depended on the porosity of the components as well as the heat treatment temperature. Components with designed, non-stochastic porosity were also produced by additive manufacturing, specifically Direct Ink Writing. Paste with suitable pseudo-plastic rheology were developed and we fabricated components with overhangs and spanning features, including highly porous 3D lattices

3D printed geopolymeric lattices: Effect of different filler materials on mechanical properties

Our group developed mixtures based on geopolymer for additive manufacturing of porous components via direct ink writing (DIW). We optimized the rheological properties in order to obtain suitable inks for the production of highly porous lattices. It should be noted that, as geopolymer mixtures are subjected to ongoing poly-condensation reactions, their viscosity changes with time in what can be seen as a 4D printing process. Different materials were added to the mixture, such as glass and plastic fibers, as well as fillers like sand, to produce innovative 3D printed geopolymeric composites. The influence of these materials on the mechanical properties was evaluated

Erratum to: Textile Reinforced Concrete: experimental investigation on design parameters

Textile Reinforced Concrete (TRC) is an advanced cement-based material in which fabrics used as reinforcement can bring significant loads in tension, allowing architects and engineers to use thin cross-sections. Previous research projects, developed during the last 10 years mainly in Germany, Israel and the USA, have shown the capabilities of such a material. In this paper an extensive experimental investigation of TRC is presented: tensile tests were carried out to obtain a complete mechanical characterization of the composite material under standard conditions, considering the influence of different variables such as reinforcement ratio, fabric geometry, curing conditions, displacement rate and specimen size. ******* Due to an unfortunate turn of events this article was published with wrong citations in the text to the references at the end of the article. In order to provide the correct information this article is hereafter published in its entirety with the correct citations and should be regarded as the final version by the reader

Follicle-like environment for domestic cat vitrified oocytes.

The in vitro development of vitrified oocytes (VOs) is still suboptimal (Mandawala et al., 2016) and the traditional two-dimensional (2D) culture systems might not be adequate to fully exploit VOs potential. The use of three-dimensional (3D) follicle-like structures, i.e. a combination of granulosa cells (GCs) and semipermeable 3D matrices, could mimic the physiological microenvironment and enhance VOs maturation and embryo development.The aim of this study was to assess the steroidogenic ability (estradiol and progesterone secretion) of GCs encapsulated in 3D barium alginate microcapsules (follicle-like structure) compared to GCs cultured in a 2D monolayer and the maturation outcomes of VOs cultured in these systems.After purification (Simsek & Arikan, 2015), cat GCs retrieved from isolated ovaries were in vitro cultured for 6 days in 3D microcapsules (Vigo et al., 2005) or in 2D monolayers. On days 2 and 6, conditioned medium was collected and hormonal determination by enzyme-linked fluorescent assay was performed. On the same days, 3D and 2D cultured GCs were used as artificial milieu for in vitro maturation of VOs obtained by Cryotop protocol. Nuclear maturation was assessed by bis-benzimide staining.Steroidogenesis was observed in 3D follicle-like structures as well as in 2D monolayers; hormonal concentration increased over time and on day 6 it significantly differed between systems (p=0.02). Vitrified oocytes resumed meiosis in presence of GCs cultured for 2 days (3D: 45.5%; 2D: 56.7%), while GCs cultured for 6 days significantly hindered VOs meiosis progression in monolayers (21.7%, p=0.007), but supported high proportions of full maturation in follicle-like structures (26.7%, p=0.07).Granulosa cells in 3D microcapsules maintained their physiological features and these follicle-like structures were able to restore VOs developmental abilities. However, further advancements in VOs culture methods would optimize the use of these valuable resources

Analytical and numerical prediction of the bending behaviour of textile reinforced concrete sandwich beams

This paper concerns the investigation of the behaviour of sandwich beams previously tested in four point bending through analytical and numerical models. Modelling is a fundamental resource to predict the mechanical response of the element and to investigate the mechanisms that act during the evolution of the test. The sandwich beams here taken into account are characterised by external textile reinforced concrete (TRC) layers and an insulation material (expanded polystyrene, EPS) able to transfer shear stresses. Bond between the layers is obtained during production thanks to an in-pressure casting technique, and no particular device is used in order to transfer shear stresses between the layers. Two beam slenderness values are taken into account. An analytical and a numerical approach have been used in order to predict the experimental behaviour: concerning the analytical approach, a model based on the Stamm and Witte sandwich theory has been developed including material non-linearity; concerning the numerical analysis, a finite element (FE) model has been built in ABAQUS including material and geometry non-linearity. The assumption of perfect bond is used in both cases. The non-linear analytical and finite element models have been validated, as a good agreement with experimental results has been achieved. The experimental identification of material parameters - TRC in tension, mortar in compression and EPS in tension, compression and shear - is crucial for the definition of proper constitutive laws for the models and is here presented and discussed. For both approaches, the assumptions of modelling TRC in bending as homogeneous and assuming perfect bond between TRC and EPS (even when behaviour becomes highly non-linear) have been proved to be reliable. Analytical and FEM results show that EPS non-linear behaviour and TRC membrane and bending behaviour govern the response. The FE analysis also highlights the mechanisms involved in specimen failure