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1145. Alternative alkali activators based on waste bottle glass and waste cathode-ray tube glassKatja Koenig, Katja Traven, Vilma Ducman, 2021, objavljeni znanstveni prispevek na konferenci Povzetek: Alkali-activated binders are an environmentally friendly alternative to Portland cement, particularly when locally-available raw materials are used. It is well known that alkali activation with a sodium silicate activator generates a hardened binder with higher compressive strength than a binder hardened with sodium hydroxide. As the alkali-silicate activators are produced through energy extensive processes, and their use can significantly increase the carbon footprint of the final products, it is of great significance to develop alternative alkaline activators based on locally-available waste materials. This article assesses the potential to apply waste bottle glass and waste cathode-ray tube (CRT) glass to synthesise alternative alkali activators by the hydrothermal method. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to determine silicon and aluminium content in the alternative activators. The influence of dissolution process parameters (time, temperature, particle size) on the concentrations of silicon and aluminium in the alternative activators was investigated. The alternative activators with silicon concentration up to 19 g/L and aluminium concentration up to 0.9 g/L were prepared at T = 120 °C and boiling time 24 h. The alternative alkali activators and, for comparison, also commercial sodium silicate were used in the alkali activation of fly ash powder. The formed pastes were cured at 70 °C for 72 h. Mechanical strength measurements indicated that alkali activation of fly ash with the optimal alternative activator yielded hardened paste with compressive strength of 33 MPa. However, the compressive strength of hardened paste prepared from fly ash and commercial sodium silicate reached 70 MPa. Part of this difference can be ascribed to the lower density of hardened pastes prepared with alternative activators.
Ključne besede: alkali -activated materials, alternative alkali activators, waste bottle glass, waste cathode -ray tube glass, fly ash, hydrothermal method
Objavljeno v DiRROS: 25.01.2024; Ogledov: 314; Prenosov: 183
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1146. Construction materials for a sustainable future : proceedings of the 2nd International Conference CoMS 2020/212021, zbornik recenziranih znanstvenih prispevkov na mednarodni ali tuji konferenci Povzetek: Zbornik pokriva številne, predvsem tehnične teme, ki so pomembne za trajnostni razvoj gradbenega sektorja, kot ključnega dejavnika pri doseganju ciljev EU za obvladovanje podnebnih sprememb in za prehod v brezogljično družbo. Vsebinsko naslavlja inovacije v gradbenih materialih in tehnologijah, vključno s komponentami za zdravo in udobno bivanje, ter interakcije med materiali in okoljem. Poleg energetske učinkovitosti stavb je v njem zajeto področje širšega razumevanja trajnostnega načrtovanja, gradnje in vzdrževanja stavb ter monitoring, ocenjevanje in modeliranje stavb. Vključuje pa tudi vsebine, ki se nanašajo na krožno gospodarstvo, kot je recikliranje materialov in komponent ter koncepti sanacij stavb, ter na digitalizacijo in avtomatizacijo področja.
Ključne besede: trajnostno gradbeništvo, trajnostna gradnja, gradbeni materiali, tehnologije, energetska učinkovitost, zborniki, elektronske knjige
Objavljeno v DiRROS: 25.01.2024; Ogledov: 376; Prenosov: 127
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1149. Temperature pre-treatment of gypsum for powder based 3D printing technologyVesna Zalar Serjun, Lidija Korat, 2021, objavljeni znanstveni prispevek na konferenci Povzetek: In recent years many researchers have been involved in studies in the field of pre-treatment of various raw materials. Temperature treatment of materials results in several advantages, which have been already recognised and successfully applied in various fields of applications. Where at the same time, the practices has been adopted also in the field of 3D printing. Enhanced strength and stiffness, assuring desirable performance criteria of the 3D printed models, reflect the most important characteristics. 3D printing binder jetting technology is based on the application of liquid binders onto powdered material, where gypsum powders have been commercially used as a base raw material. As natural raw materials can be replaced by other materials, such as recycled industrial by products, the aim of this research work was to evaluate the potential usage of three synthetic gypsum powders from different industrial processes for 3D printing. The investigation covered (a) mineralogical and microstructural characteristics of gypsums from different origin and (b) the effect of pre-treatment of gypsum powders at different temperatures (up to 500 °C). On the basis of the results, the most promising temperature regime for each different waste gypsum powder treatment, reflecting in the most optimal setting time, was defined. Synthetic gypsums were characterized by X-ray diffraction (QXRD), scanning electron microscopy (SEM) and differential thermal analysis (TG/DTA). The results showed that all three synthetic gypsums (calcium sulfate dihydrate, CaSO 4∙2H2O) thermally degrade into calcium sulfate anhydrite (CaSO 4) via an intermediate calcium sulfate hemihydrate (CaSO 4∙ ½H2 O, bassanite) phase. Microstructural and mineralogical differences were observed when temperature treated gypsums from different origins were compared. The detailed knowledge of gypsum powder properties at different temperature regime is important parameter for the assurance of 3D printing key parameters such as flowability, roughness and wettability, especially for determination of saturation levels and setting time. After all, these parameters define final mechanical properties of 3D printed structures. By using such approach, the understanding of material compatibility for 3D printing technology can be defined and improved if necessary.
Ključne besede: 3D print, additive manufacturing, gypsum, temperature
Objavljeno v DiRROS: 25.01.2024; Ogledov: 346; Prenosov: 191
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