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SMART CONCRETE FOR URBAN AREAS: IMPROVED PERFORMANCE AND SUSTAINABILITY OF FUNCTIONALIZED GRAPHENE RELATED MATERIALS IN CEMENTITIOUS PRODUCTS
Get PDFQuesto lavoro riassume i più interessanti risultati sperimentali raggiunti durante il dottorato industriale promosso in collaborazione tra Italcementi S.p.A. ed il Dipartimento di Scienze Chimiche dell'Università degli Studi di Padova.
I compositi cementizi (pasta cementizia, malta e calcestruzzo) sono i materiali da costruzione più performanti e largamente impiegati in campo edilizio. D'altro canto, in un'ottica di miglioramento continuo, rientra la progettazione di mix design sempre più innovativi, con ambizione almeno duplice. Da un lato, lo sforzo resta orientato sull'incremento della resistenza a trazione e della capacità di deformazione, per ridurne la fragilità. Dall'altro, diventa prioritario affiancare, alla proposta di applicazioni tecnicamente avanzate, soluzioni che soddisfino gli attuali requisiti di sostenibilità ambientale e sociale (oltre che economica) del loro impatto.
L’utilizzo di nanomateriali sembrerebbe essere tra le migliori risposte ad ambo le urgenze; in particolare, se impiegati in combinazione con agenti superfluidificanti atti a favorirne una più omogenea dispersione in matrice cementizia.
Grazie alle loro elevate aree superficiali e resistenza alla trazione, i graphene based materials (GBMs) sono considerati i nanomateriali più promettenti per migliorare le proprietà meccaniche dei materiali compositi cementizi (CCMs). Se ben dispersi, i GBMs possono promuovere l'edilizia sostenibile, permettendo di realizzare malte e calcestruzzi con ridotti contenuti di cemento e minore impronta carbonica, preservandone le consolidate proprietà meccaniche e di durabilità. A causa della loro scarsa dispersione in mezzi acquosi, un'efficace distribuzione di GBMs in matrice cementizia è particolarmente impegnativa.
Tra le più sfidanti soluzioni per migliorare la dispersione dei GBMs in ambiente acquoso la funzionalizzazione covalente con gruppi idrofili riveste un ruolo di particolare rilievo.
Questa ricerca di dottorato si è concentrata sulla funzionalizzazione covalente di GBMs commerciali, per ottenere nanomateriali idrofili in grado di essere omogeneamente dispersi in matrice cementizia.
In primo luogo, abbiamo funzionalizzato il grafene a strato singolo (SLG) legandolo chimicamente con diverse aniline para-sostituite. Più in dettaglio, abbiamo modificato i SLG tramite la reazione di Tour, introducendo gruppi solfonati, catene polietilenglicole o gruppi ammonio quaternari. Abbiamo altresì replicato questa reazione utilizzando diversi GBMs: pregiati grafene few layers, grafene nanoplatelest di alta e bassa qualità, individuando i GBM e i gruppi funzionali più adatti per ottenere rese di funzionalizzazione elevate.
Successivamente, abbiamo studiato il ruolo dei GBMs funzionalizzati per migliorare le prestazioni meccaniche dei CCMs, preparando campioni di malta con diverse percentuali di prodotti a base di grafene. Inoltre, abbiamo valutato due diverse procedure di miscelazione, combinando approcci meccanici e chimici per potenziare ulteriormente la dispersione dei GBM nella matrice cementizia.
I risultati della ricerca condotta in questo percorso di dottorato delineano nuove prospettive per un uso più efficace e consapevole dei GBMs nella progettazione ed applicazione di materiali cementizi non solo tecnologicamente avanzati ma anche ambientalmente sostenibili.This work resumes the most interesting experimental results achieved during the industrial PhD signed between Italcementi S.p.A and the Department of Chemical Sciences of the Università degli Studi di Padova.
Cement composite materials (CCMs), that include paste, mortar, and concrete, are the most widely used and highly performing construction materials. Nevertheless, extensive efforts are still necessary to improve their tensile strength and strain capacity, and to reduce their brittle nature. Several studies have been focused to address these problems, concerning the addition of specific admixtures, nanomaterials, or their combined use. Among them, Graphene Based Materials GBMs (graphene, graphene oxide, graphene nanoplatelets, etc.), thanks to their high surface areas, tensile strength, and aspect ratio, represent the ideal candidates to enhance the properties of cementitious materials. If well dispersed into cementitious matrix, GBMs can promote sustainable building, consuming less cement (preserving mechanical properties), emitting less CO2, showing excellent durability, and reducing construction cycle time thanks their high early strength.
Despite their excellent intrinsic properties, the incorporation of GBMs in cementitious matrix is particularly challenging due to their poor dispersion in aqueous media.
A possible solution to improve the dispersibility of GBMs in water environment is their covalent functionalization with hydrophilic groups, that requires the addition of specific moieties that form covalent bonds on the basal plane of the carbon lattice.
This doctoral research was focused on the covalent functionalization of commercial GBMs, increasing their hydrophilicity and preparing new compounds able to be homogeneously dispersed in cementitious matrix.
Firstly, we functionalized single layer graphene (SLG) attaching different para-substituted anilines. More in detail, we modified SLG by the Tour reaction, introducing sulfonate group, polyethylene glycol chain, or a quaternary ammonium group. We also replicated this reaction using different GBMs: few layers graphene, high-quality graphene nanoplatelets, and low-quality graphene nanoplatelets, finding the most suitable GBMs and functional groups to obtain high functionalization yields.
Subsequently, we investigated the role of functionalized GBMs to improve mechanical performance of CCMs by preparing mortar samples with different percentage of graphenic products. Moreover, we evaluated two different mixing procedures, combining mechanical and chemical approaches to further enhance the dispersibility of GBMs in the cementitious matrix.
The fruitful research carried out in the PhD path provides new perspectives for a more effective and aware use of GBMs in performing as well as sustainable cementitious building materials
Composito fotocatalitico a base di Kassite e Perovskite e prodotti cementizi che lo contengono
No full textFunctionalized graphene-based materials for cementitious applications
No full textGraphene-based materials (GBM) are promising cementitious composite additives that can significantly improve the mechanical characteristics and durability of concrete due to their unique properties, such as high surface area and aspect ratio and excellent tensile strength, to name a few. To display their full potential, GBM have to be homogeneously dispersed into the aqueous environment of cement-based matrices. The present study addresses the issue of limited dispersibility in the aqueous media of GBM through the chemical functionalization of mono- and few-layer graphene structures with hydrophilic aryl sulfonate groups and shows that a series of mortar samples containing modified GBM exhibit increased flexural and compressive strength by up to 17% and 30%, respectively, compared to mortar references without additives.Few-layer graphene, functionalized with covalently attached arylsulfonate groups, is proposed as an additive to improve the compressive and flexural strength of concrete towards smart and sustainable building materials
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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