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1142. LCA and LCC assessment of UHPFRC application for railway steel bridge strengtheningIrina Stipanović, Sandra Škarić Palić, Aljoša Šajna, Martín-Sanz Henar, Eleni Chatzi, 2021, published scientific conference contribution Abstract: Most of the existing railway steel bridges are nowadays older than 70 years, experiencing serious aging and overload problems. Therefore they either need to be replaced or strengthened to fulfil the increased requirements. The main idea of strengthening existing steel bridges is considering the possibility of adding load bearing deck above the main girders without replacing them. In this particular case study, the original steel structure of the 9m long railway bridge was dismantled and transported to the laboratory for the experimental assessment and development of the new rehabilitation method. Based on the assessment results, a strengthening slab was designed using Ultra High Performance Fibre Reinforced Concrete (UHPFRC) formula. In the life cycle analysis, using LCC and LCA models, the comparison of the application of UHPFRC cast in-situ deck is compared to the bridge replacement solution, which was actually selected method by the owner. The executed solution used also a temporary bridge in order to enable continuous traffic, which has caused very high construction costs. In order to compare different options, we have additionally analysed a solution without a temporary bridge, which created three life cycle scenarios. Most important steps during the construction, exploitation and end-of-life stage have been taken into account and integrated into the LCA and LCC models. Finally the environmental, economy and societal impacts of three solutions were compared over the period of 60 years. The rehabilitation option with UHPFRC deck has shown by far the lowest direct and environmental cost while the user delay costs only after the period of 50 years are not the most convenient for users. Superior characteristics of UHPFRC enabled the optimization of the load bearing deck and by that a very low total used quantity of material resulting in minimum direct and indirect costs.
Keywords: railway steel bridge, UHPFRC, strengthening, LCA, LCC model
Published in DiRROS: 25.01.2024; Views: 234; Downloads: 161
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1145. Experimental carbonation study for durability assessment of novel cementitious materialsSebastijan Robič, Aljoša Šajna, Lucija Hanžič, Alisa Machner, Marie Helene Bjørndal, Klaartje De Weerdt, Yushan Gu, Benoit Bary, Rosamaria Lample, 2021, published scientific conference contribution Abstract: The design process of concrete structures is carried out using standards and guidelines, while the durability predictions of concrete structures is supported only with exposure classes and experience-based requirements. To improve durability predictions of the carbonation resistance of concrete, a numerical model is being developed within the Horizon 2020 project EnDurCrete, coupling the rate of carbonation, and the drying rate. To verify the numerical model, an accelerated carbonation study was carried out. Experiments were conducted on mortars incorporating a novel CEM II/C (S-LL) cement, developed within the EnDurCrete project, and a commercially available reference cementCEM II/A-S. EnDurCrete mortars (EnM) and reference mortars (RefM) were prepared with water-cement ratios of 0.6 and 0.5 (denoted with label extensions -06 and -05). Visual assessments and thermogravimetric analysis (TGA) were used to measure the carbonation rates, which were found to be ~1.0 mm day-0.5 in EnM-06 and ~0.6 mm day-0.5 in RefM-06, while in EnM-05 and RefM-05 the values were ~0.7 and ~0.2 mm day-0.5 respectively. Additionally, TGA shows that the initial portlandite (CH) content is ~1.5 wt% in EnM-06 as opposed to ~3.0 wt% in RefM-06. The difference in the initial CH content in the two hydrated binders might explain the difference in their carbonation rate. During the moisture transport experiments a gravimetric method was used to determine mass changes as specimens underwent drying and resaturation with and without CO2 present. The drying led to a decrease in mass, but in the presence of CO2 this mass loss was compensated by the mass gain due to uptake of CO2 during carbonation. The resaturation experiments indicate an increase in the suction porosity in the carbonated samples compared to the non-carbonated samples.
Keywords: concrete, absorption of water, carbonation, durability assessment, model verification
Published in DiRROS: 25.01.2024; Views: 265; Downloads: 178
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1147. Mud from the Sitarjevec mine as a pigment for textile printingDarja Rant, Mateja Štefančič, Vesna Zalar Serjun, Mateja Golež, 2021, published scientific conference contribution Abstract: The Sitarjevec mine, located near the town of Litija (Central Slovenia), is recognized by the strong yellow colour of its dripstone structures and mine mud deposits. The mine mud, composed predominantly of goethite, accumulates on the ground of the mine shafts as the result of the interaction between percolating underground water, iron ore minerals and microorganisms. Since the accumulation of limonite mine mud is an ongoing process, larger quantities of mud have been deposited in the mine shafts since its closure. These deposits present a real threat of unleashing a mine mud spill on the town of Litija. Such a scenario has already previously occurred. In order to find new potential routes for recycling larger quantities of this mine mud, the present research work was performed to assess the use of mine mud as a pigment in the dye industry. In the first stage, the chemical (XRF) and microstructural (SEM) characteristics of the mine mud were defined together with the identification of its phase composition (XRD), particle size distribution and specific surface area (BET). Furthermore, the pigment was used to colour textile printing paste on a laboratory scale. To define the most appropriate quality of textile prints the rheological response of the various textile printing paste samples was investigated in terms of their plastic viscosity, indicating their suitability for use in textile printing. Test prints wereconducted, and the properties of leaching and fastness in the prints were assessed.
Keywords: mine mud, recycling, pigment, printing paste, textile, rheology
Published in DiRROS: 25.01.2024; Views: 271; Downloads: 151
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1150. Strictures of the male urethra: how to perform and evaluate radiourethrography and sonourethrography to avoid mistakesDarja Babnik-Peskar, Alenka Višnar-Perovič, 2000, original scientific article Abstract: Introduction. Precise evaluation of the uretheral stricture localisation, length, depth and quality of wall changes are necessary for the selection of the optimal treatment to prevent recurrences. Decision for urethral dilatation, internal urethrotomy or open surgery depends on urethroscopic, radiourethrographic-RUG, and recently, according to MC Annich, also sonourethrographic-SUG results. SUG adds information about the depth and density of spongiofibrosis. Previously published findings of RUG length underestimation, compared to SUG and endoscopy, were responsible for inappropriate treatment and recurrences. In our article, we evaluate SUG as a new imaging method in the diagnosis of uretheral strictures and treatment planning, and describe both imaging methods together with usual pitfalls in performance or interpretation, possible reason for incorrect length measurements, and RUG length underestimation. Patients and methods. In the period of 20 months, we evaluated SUG compared to RUG and endoscopy in 51/130 males with suspected urethral strictures. Results. Compared to RUG, sonographywas correct in 92% radiographycally detected strictures. Length measurements by sonography were 22% shorter than radiographic lengths, which could be explained by radiographic magnification, as it was proved with wire measure placed on penis. Considering radiographic magnification, we did not find important differences in any measurement. Opposite to previously published RUG results compared to endoscopy and SUG, radiographic length underestimation was not found. Conclusions. The combination of both imaging methods provides optimal information about urethral stricture anatomy. We conclude that published radiographic length underestimation could be only a misinterpretation. (Abstract truncated at 2000 characters).
Published in DiRROS: 25.01.2024; Views: 218; Downloads: 53
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