The purpose of this experimental study is the valorisation of industrial waste, specifically waste from the cutting of marble slabs and from the production of sodium silicate or sodium silicate obtained from foundry sands as reagents, for the synthesis of a concrete accelerator based on calcium silicate hydrate (C-S-H). The synthesis was carried out by precipitation from a suspension of calcium carbonate with commercial sodium silicate, controlling the nucleation and growth conditions, to obtain a nanocrystalline C-S-H precipitate. Several tests were performed to maximize the reaction yield and minimize the precipitation time, on the basis of preliminary thermodynamic simulations. Structural studies on the precipitate were carried out by X-ray diffraction on powders at defined time intervals, thus monitoring the trend of the reaction over time and the changes in phase assembly and in the C-S-H structure. Further microstructural analysis was based on images obtained by high resolution scanning electron microscopy (SEM). The study on the accelerator efficacy was conducted through calorimetric analysis, compared with a concrete hardening accelerator of the same type presently on the market. Furthermore, with the aim of limiting the crystalline growth, the use of polymeric admixtures in the formulation of the accelerator was tested, after measurements of zeta potential of the precipitate as a guide for their choice. This study constitutes a basis for future experiments with the aim of improving the performance of the accelerator and for other studies in the field of valorisation of solid precipitates from complex fluids deriving from industrial waste or by-products.
Il lavoro sperimentale svolto ha lo scopo di valorizzare gli scarti industriali, in particolare scarti del taglio di lastre di marmo (marmettola) e scarti dalla produzione del silicato di sodio o silicato di sodio ricavato da terre di fonderia, utilizzandoli come reagenti per la sintesi di un accelerante per calcestruzzo a base di silicato di calcio idrato (C-S-H). La sintesi viene condotta per precipitazione da una sospensione di carbonato di calcio con silicato di sodio commerciale, controllandone le condizioni di nucleazione e crescita, allo scopo di ottenere un precipitato di C-S-H nanocristallino. Si effettuano diverse prove allo scopo di massimizzare la resa di reazione e di minimizzare i tempi di precipitazione, sulla base delle simulazioni termodinamiche previamente condotte. Gli studi strutturali sul precipitato vengono fatti tramite diffrazione a raggi X su polveri ad intervalli di tempo definiti e puntuali, monitorando così l’andamento della reazione nel tempo e i cambiamenti nell’assemblaggio delle fasi e nella struttura stessa del C-S-H. Ulteriore analisi microstrutturale è condotta sulla base delle immagini ottenute tramite microscopia elettronica a scansione (SEM) ad alta risoluzione. Lo studio sull’efficacia accelerante del prodotto di sintesi viene condotto tramite analisi calorimetrica, confrontandolo con un accelerante della stessa tipologia attualmente in commercio. Inoltre, nell’intento di limitare la crescita cristallina si svolgono prove con l’utilizzo di additivi nella formulazione dell’accelerante, scelti in seguito a misure di potenziale zeta. Questo studio pone le basi per successive sperimentazioni con lo scopo di migliorare le prestazioni dell’accelerante in questione o per altri studi nell’ambito della valorizzazione di precipitati solidi da miscele complesse derivanti da scarti o sottoprodotti industriali.
Controllo e valorizzazione dei precipitati solidi da fluidi industriali multicomponenti complessi.
LONGO, VERONICA
2022/2023
Abstract
The purpose of this experimental study is the valorisation of industrial waste, specifically waste from the cutting of marble slabs and from the production of sodium silicate or sodium silicate obtained from foundry sands as reagents, for the synthesis of a concrete accelerator based on calcium silicate hydrate (C-S-H). The synthesis was carried out by precipitation from a suspension of calcium carbonate with commercial sodium silicate, controlling the nucleation and growth conditions, to obtain a nanocrystalline C-S-H precipitate. Several tests were performed to maximize the reaction yield and minimize the precipitation time, on the basis of preliminary thermodynamic simulations. Structural studies on the precipitate were carried out by X-ray diffraction on powders at defined time intervals, thus monitoring the trend of the reaction over time and the changes in phase assembly and in the C-S-H structure. Further microstructural analysis was based on images obtained by high resolution scanning electron microscopy (SEM). The study on the accelerator efficacy was conducted through calorimetric analysis, compared with a concrete hardening accelerator of the same type presently on the market. Furthermore, with the aim of limiting the crystalline growth, the use of polymeric admixtures in the formulation of the accelerator was tested, after measurements of zeta potential of the precipitate as a guide for their choice. This study constitutes a basis for future experiments with the aim of improving the performance of the accelerator and for other studies in the field of valorisation of solid precipitates from complex fluids deriving from industrial waste or by-products.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/47466