1481. Influence of homogenization of alkali-activated slurry on mechanical strengthBarbara Horvat, Mark Češnovar, Katja Traven, Majda Pavlin, Katja Koenig, Vilma Ducman, 2022, published scientific conference contribution Abstract: Alkali-activated materials are promising materials for the construction industry due to the accessibility of the precursors, which are mainly secondary industrial by-products, and their cost- effective and energy-efficient production. Although these materials are not new, some of the parameters in the technological process are not yet fully understood and tested. Therefore, in this paper in the means of mechanical strength, the preparation of alkali-activated pastes by using a three-roll mill homogenization method is discussed. The influence of homogenization of alkali- activated slurry has been evaluated on different waste materials (fly ash, fly ash with metakaolin, slag mixture (electric arc furnace slag and ladle slag), glass wool, waste green ceramics), which are treated with different alkali activators (NaOH, commercial sodium silicate solution, laboratory-produced alkali activators based on waste cathode- ray tube glass) with different curing regimes (60 °C and 70 °C) and different drying methods (drying at room temperature, drying at 105 °C). The viscosity of the slurry before homogenization was higher than after homogenization, the distribution of elements was more uniform and the compressive strength higher in all homogenized alkali activated materials, regardless of other parameters.
Keywords: secondary raw material, alkali activated material, foaming, homogenization, mechanical strength
Published in DiRROS: 21.12.2023; Views: 335; Downloads: 112
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1482. The development and assessment of alkali activated paving blocksAna Frankovič, Vilma Ducman, Lubica Kriskova, Efthymios Tatsis, Petrica Petrica, Yiannis Pontikes, 2022, published scientific conference contribution Abstract: In recent years great attention has been placed by the building sector on alkali-activated technology based on metakaolin, fly ash and ground granulated blast furnace slag (GGBFS), but also on emerging precursors such as by-products from non-ferrous metallurgy. The present work focuses on the development of alkali-activated binders from two slags, one from primary and one from secondary copper production, which were finely milled, blended with GGBFS, and activated with K-based alkali silicate solution with a 1.7 SiO2/K2O molar ratio. The aggregate to paste mass ratio was 2. The mixtures were cast, and cured for a designated time at room temperature and 60% RH. The so-obtained paving blocks were then tested in accordance with European standard for concrete paving blocks. The following properties were measured: splitting tensile strength, abrasion resistance, slip and skid resistance, resistance to freeze-thaw and resistance to freeze-thaw in the presence of de-icing salts. Their properties were compared to those of commercially available concrete paving blocks, and it was found that the performance of the alkali-activated pavers was generally comparable with the concrete pavers, while certain properties (e.g., abrasion resistance, freeze-thaw resistance and freeze-thaw resistance in presence of de-icing salts) were considerably better.
Keywords: slags, alkali activated pavers, properties
Published in DiRROS: 21.12.2023; Views: 243; Downloads: 157
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1483. Getting more out of existing structuresMartín-Sanz Henar, Konstantinos Tatsis, Domagoj Damjanovic, Irina Stipanović, Aljoša Šajna, Ivan Duvnjak, Uroš Bohinc, Eugen Brühwiler, Eleni Chatzi, 2019, original scientific article Abstract: Ultra-high-performance fiber-reinforced cement-based composite (UHPFRC) has been increasingly adopted for rehabilitation projects over the past two decades, proving itself as a reliable, cost-efficient and sustainable alternative against conventional methods. High compressive strength, low permeability and high ductility are some of the characteristics that render UHPFRC an excellent material for repairing existing aged infrastructure. UHPFRC is most commonly applied as a surface layer for strengthening and rehabilitating concrete structures such as bridge decks or building slabs. However, its implementation with steel structures has so far been limited. In this work, the UHPFRC strengthening of a steel bridge is investigated both in simulation as well as in the laboratory, by exploiting a real-world case study: the Buna Bridge. This Croatian riveted steel bridge, constructed in 1893, repaired in 1953, and decommissioned since 2010, was removed from its original location and transported to laboratory facilities for testing prior to and after rehabilitation via addition of UHPFRC slab. The testing campaign includes static and dynamic experiments featuring state-of-the-art monitoring systems such as embedded fiber optics, acoustic emission sensors and digital image correlation. The information obtained prior to rehabilitation serves for characterization of the actual condition of the structure and allows the design of the rehabilitation solution. The UHPFRC slab thickness was optimized to deliver optimal fatigue and ultimate capacity improvement at reasonable cost. Once the design was implemented, a second round of experiments was conducted in order to confirm the validity of the solution, with particular attention allocated to the interface between the steel substrate and the UHPFRC overlay, as the connection between both materials may result in a weak contact point. A detailed fatigue analysis, based on updated FEM models prior to and after strengthening, combined with the results of a reliability analysis prove the benefits of adoption of such a solution via the significant extension of the structural lifespan.
Keywords: bridge, steel, UHPFRC, structures
Published in DiRROS: 21.12.2023; Views: 294; Downloads: 114
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1484. Merjeni in izračunani fotobiološki učinki odbite svetlobe na ljudiKatja Malovrh Rebec, 2018, original scientific article Abstract: Pri načrtovanju osvetlitve izračuni le delno napovejo vplive svetlobe na uporabnike prostorov. Svetloba ima namreč poleg dobro poznanih slikovnih učinkov, ki jih možgani interpretirajo na podlagi odzivov čepkov in paličic, tudi neslikovne učinke. Ti ne pripomorejo k orientaciji v prostoru, temveč sporočajo telesu ključne informacije, ki vplivajo na tvorbo hormonov. Vrh te zaznave je v modrem delu spektra vidne svetlobe. Žal delovanja teh fotoreceptorjev še ne opisujemo s parametri, ustaljenimi v praksi projektiranja, zato so vplivi na uporabnike pogosto prezrti. Dodaten izziv pomeni praksa, pri kateri svetlobne učinke preračunavamo v lukse, kar pomeni, da jih množimo s povprečnim človeškim dnevnim vidom. Tak pristop ni primeren za vrednotenje neslikovnih učinkov, ker imajo drugo akcijsko krivuljo. Izmerili smo spektralno sestavo odbitih dnevnih svetlob v modelnem prostoru, ker nas je zanimalo, kakšne razlike nastanejo v slikovni in neslikovni zaznavi, če pobarvamo stene z različnimi barvami. Modra in vijoličasta stena neslikovno stimulirata opazovalca bolj kot slikovno v obeh opazovanih smereh pogleda, oranžna v obeh primerih neslikovno vpliva manj, pri zeleni pa je bila neslikovna zaznava bolj stimulirana od slikovne pri pogledu naprej, pri pogledu v mizo pa je bilo obratno.
Keywords: svetloba, fotobiološki vpliv, spektralna sestava svetlobe, dnevna svetloba
Published in DiRROS: 21.12.2023; Views: 294; Downloads: 100
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1485. Degradation and Stabilization of Polymer MaterialsBranka Mušič, Andrijana Sever Škapin, 2023, other scientific articles Keywords: polymer-based materials, nano, micro, and macro composites, effects on (micro) organisms and toxicity, impact on the ecosystem, mechanisms and products of accelerated aging and degradation, physical, chemical, mechanical, thermal, and morphological, analysis, biodegradability, sustainability, life cycle, renewable and recycled resources and the circular economy
Published in DiRROS: 21.12.2023; Views: 355; Downloads: 122
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1487. Tehnične smernice za ohranjanje in rabo genskih virov : brek = Sorbus torminalisRobert Brus, Zvone Sadar, Primož Štular, Hojka Kraigher, 2013, professional article Keywords: genski viri, drevesne vrste, tehnične smernice, brek, Sorbus torminalis, Slovenija
Published in DiRROS: 20.12.2023; Views: 456; Downloads: 96
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1490. Tehnične smernice za ohranjanje in rabo genskih virov : lipa in lipovec = Tilia platyphyllos, Tilia cordataIgor Dakskobler, Robert Brus, Andrej Verlič, Nikica Ogris, Gregor Božič, 2013, professional article Keywords: genski viri, drevesne vrste, tehnične smernice, lipa, Tilia platyphyllos, lipovec, Tilia cordata, Slovenija
Published in DiRROS: 20.12.2023; Views: 341; Downloads: 0 |
