31. Pathway toward sustainable winter road maintenance (case study)Katja Malovrh Rebec, Janez Turk, 2023, independent scientific component part or a chapter in a monograph Abstract: Life Cycle Assessment (LCA) method was applied to evaluate the environmental impacts of winter road maintenance managed by an innovative road-weather information system and the impacts of vehicles passing the road during the snowstorm event. A case study refers to 10-hour lasting snowstorm event, considering a specific road section and application of a road-weather information management system to help winter road maintenance agency optimizing activities (salt gritting and/or plowing). Reliable information on the timing of the beginning of the snowstorm event affects (1) the activities of winter road maintenance, (2) the mobility of all vehicles passing the road, and (3) the fuel consumption of the vehicles. Since activities are optimized in case of preventive operation of winter road maintenance, less salt is needed overall. The road remains free of snow cover in case of preventive winter road maintenance operation, meaning that passenger cars and trucks pass the road at normal speed, without undesirable acceleration and braking caused by wheels slipping if snow accumulates on the road. Fuel consumption of vehicles passing salted and snow-free road remains unchanged, while fuel consumption increases in case of snow cover. Reduction of environmental burdens in case of such optimized winter road maintenance operation, is shown in this case study. The overall results of the comparative LCA analysis showed that the use of the road-weather information system in road traffic allows for as much as 25% reduction of environmental footprints. In the scenario where the winter service does not use information system the winter service also uses 40% more salt, which is also related with additional environmental impacts.
Keywords: LCA, okoljski odtisi, cesta, snežne razmere, preventivno delovanje, promet, poraba goriva, varnost, LCA, environmental impacts, road, snow cover, preventive operation, traffic, fuel consumption, safety
Published in DiRROS: 11.12.2023; Views: 172; Downloads: 108
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32. Pozicioniranje in kontrola kakovosti mamogramaZvonko Krajnc, Miljeva Rener, Alenka Rataj, Patricija Rusjan, Gregor Novak, Katja Čebulj, 2004, published scientific conference contribution Abstract: Izhodišča. Pravilno pozicioniranje je predpogoj za zagotavljanje kakovosti mamografskih slik. Zato je pomembno, da dobro poznamo anatomijo in tehnike pozicioniranja, slikanja in razvijanja. Zaključki. Da bi dosegli optimalen prikaz tkiv, rnorarno pravilno nastaviti nosilec kasete in kompresorij ter izkoristiti premakljivost dojk, pomembna pa je tudi pravilna uporaba aparatur.Ob izvajanju mamografije moramo nujno upoštevati kriterije za kontrolo kakovosti. Pri tem nam pomaga pravilnik o pogojih, ki jih morajo izpolnjevati primarni centri za dojke v Republiki Sloveniji, ter evropske smernice. S kontrolo kakovosti bomo u Sloveniji zvišali kvaliteto in s tem prispevali k čirn zgodnejšemu odkrivanju sprememb na dojkah.
Published in DiRROS: 01.12.2023; Views: 214; Downloads: 52
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34. Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAMKatja Traven, Mark Češnovar, Vilma Ducman, 2019, original scientific article Abstract: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Keywords: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Published in DiRROS: 22.11.2023; Views: 253; Downloads: 132
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36. RILEM TC 247-DTA round robin test : mix design and reproducibility of compressive strength of alkaliactivated concretesJohn L. Provis, Kamel Arbi, Susana Bernal, Dali Bondar, Anja Buchwald, Arnaud Castel, Sundararaman Chithiraputhiran, Martin Cyr, Alireza Dehghan, Katja Dombrowski-Daube, Ashish Dubey, Vilma Ducman, Gregor J. G. Gluth, Sreejith Nanukuttan, Karl Peterson, Francisca Puertas, Arie van Riessen, Manuel Torres-Carrasco, Guang Ye, Yibing Zuo, 2019, original scientific article Abstract: The aim of RILEM TC 247-DTA Durability Testing of Alkali-Activated Materials is to identify and validate methodologies for testing the durability of alkali-activated concretes. To underpin the durability testing work of this committee, five alkali-activated concrete mixes were developed based on blast furnace slag, fly ash, and flash-calcined metakaolin. The concretes were designed with different intended performance levels, aiming to assess the capability of test methods to discriminate between concretes on this basis. A total of fifteen laboratories worldwide participated in this round robin test programme, where all concretes were produced with the same mix designs, from single-source aluminosilicate precursors and locally available aggregates. This paper reports the mix designs tested, and the compressive strength results obtained, including critical insight into reasons for the observed variability in strength within and between laboratories.
Keywords: alkali-activated materials (AAM), mechanical properties, test method, Rilem TC, durability
Published in DiRROS: 14.09.2023; Views: 235; Downloads: 138
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37. The potential of ladle slag and electric arc furnace slag use in synthesizing alkali activated materials; the influence of curing on mechanical propertiesMark Češnovar, Katja Traven, Barbara Horvat, Vilma Ducman, 2019, original scientific article Abstract: Alkali activation is studied as a potential technology to produce a group of high performance building materials from industrial residues such as metallurgical slag. Namely, slags containing aluminate and silicate form a useful solid material when activated by an alkaline solution. The alkali-activated (AA) slag-based materials are promising alternative products for civil engineering sector and industrial purposes. In the present study the locally available electric arc furnace steel slag (Slag A) and the ladle furnace basic slag (Slag R) from different metallurgical industries in Slovenia were selected for alkali activation because of promising amorphous Al/Si rich content. Different mixtures of selected precursors were prepared in the Slag A/Slag R ratios 1/0, 3/1, 1/1, 1/3 and 0/1 and further activated with potassium silicate using an activator to slag ratio of 1:2 in order to select the optimal composition with respect to their mechanical properties. Bending strength of investigated samples ranged between 4 and 18 MPa, whereas compressive strength varied between 30 and 60 MPa. The optimal mixture (Slag A/Slag R = 1/1) was further used to study strength development under the influence of different curing temperatures at room temperature (R. T.), and in a heat-chamber at 50, 70 and 90 °C, and the effects of curing time for 1, 3, 7 and 28 days was furthermore studied. The influence of curing time at room temperature on the mechanical strength at an early age was found to be nearly linear. Further, it was shown that specimens cured at 70 °C for 3 days attained almost identical (bending/compressive) strength to those cured at room temperature for 28 days. Additionally, microstructure evaluation of input materials and samples cured under different conditions was performed by means of XRD, FTIR, SEM and mercury intrusion porosimetry (MIP).
Keywords: alkali activation, slag, influence of curing regime, FTIR
Published in DiRROS: 13.09.2023; Views: 261; Downloads: 143
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38. Evaluation of locally available amorphous waste materials as a source for alternative alkali activatorsKatja Koenig, Katja Traven, Majda Pavlin, Vilma Ducman, 2021, original scientific article Abstract: The production of alkali-activated materials with excellent mechanical performance requires the use of waterglass, which has a significant carbon footprint. Such materials can have a lower carbon footprint if we replace water glass with alternative activators sourced from waste. In this study, we assessed the suitability of locally available amorphous waste materials (stone wool, glass wool, bottle glass and cathode-ray tube glass) as a source for the preparation of alternative alkali activators. We quantified the amount of silicon and aluminium dissolved in the activator solutions via inductively coupled plasma-optical emission spectrometry. The alternative activators were then used to produce alkali-activated fly ash and slag. The compressive strength values of alkali-activated fly ash specimens upon the addition of NaOH, water glass and the most promising alternative activator were 38.98 MPa, 31.34 MPa and 40.37 MPa, respectively. The compressive strength of slag specimens activated with alternative activators with the highest concentration of dissolved silicon (21 g/L) was, however, 70% higher than the compressive strength of slag specimens activated with only 10 M sodium hydroxide. The compressive strength of slag specimens with the addition of the most promising alternative activator was significantly lower (3.5 MPa) than the compressive strength of those that had been activated by commercial water glass (34.3 MPa).
Keywords: alkalijsko aktivirani materiali, alternativni aktivatorji, lastnosti, alkali activated materials/geopolimers, alternative activators, properties
Published in DiRROS: 22.08.2023; Views: 220; Downloads: 150
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39. RILEM TC 247-DTA round robin test : carbonation and chloride penetration testing of alkali-activated concretesGregor J. G. Gluth, Kamel Arbi, Susana Bernal, Dali Bondar, Arnaud Castel, Sundararaman Chithiraputhiran, Alireza Dehghan, Katja Dombrowski-Daube, Ashish Dubey, Vilma Ducman, Karl Peterson, Penny Pipilikaki, Siska L. A. Valcke, Guang Ye, Yibing Zuo, John L. Provis, 2020, original scientific article Abstract: Many standardised durability testing methods have been developed for Portland cement-based concretes, but require validation to determine whether they are also applicable to alkali-activated materials. To address this question, RILEM TC 247-DTA "Durability Testing of Alkali-Activated Materials" carried out round robin testing of carbonation and chloride penetration test methods, applied to five different alkali-activated concretes based on fly ash, blast furnace slag or metakaolin. The methods appeared overall to demonstrate an intrinsic precision comparable to their precision when applied to conventional concretes. The ranking of test outcomes for pairs of concretes of similar binder chemistry was satisfactory, but rankings were not always reliable when comparing alkali-activated concretes based on different precursors. Accelerated carbonation testing gave similar results for fly ash-based and blast furnace slag-based alkali-activated concretes, whereas natural carbonation testing did not. Carbonation of concrete specimens was observed to have occurred already during curing, which has implications for extrapolation of carbonation testing results to longer service life periods. Accelerated chloride penetration testing according to NT BUILD 443 ranked the tested concretes consistently, while this was not the case for the rapid chloride migration test. Both of these chloride penetration testing methods exhibited comparatively low precision when applied to blast furnace slag-based concretes which are more resistant to chloride ingress than the other materials tested.
Keywords: alkali-activated materials (AAM), carbonatization, chloride penetration, Rilem TC, durability
Published in DiRROS: 17.08.2023; Views: 252; Downloads: 170
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40. RILEM TC 247-DTA round robin test : sulfate resistance, alkali-silica reaction and freeze-thaw resistance of alkali-activated concretesFrank Winnefeld, Gregor J. G. Gluth, Susana Bernal, Maria Chiara Bignozzi, Lorenza Carabba, Sundararaman Chithiraputhiran, Alireza Dehghan, Sabina Dolenec, Katja Dombrowski-Daube, Ashish Dubey, Vilma Ducman, Yu Jin, Karl Peterson, Stephen Dietmar, John L. Provis, 2020, original scientific article Abstract: The RILEM technical committee TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ conducted a round robin testing programme to determine the validity of various durability testing methods, originally developed for Portland cement based-concretes, for the assessment of the durability of alkali-activated concretes. The outcomes of the round robin tests evaluating sulfate resistance, alkali-silica reaction (ASR) and freeze–thaw resistance are presented in this contribution. Five different alkali-activated concretes, based on ground granulated blast furnace slag, fly ash, or metakaolin were investigated. The extent of sulfate damage to concretes based on slag or fly ash seems to be limited when exposed to an Na2SO4 solution. The mixture based on metakaolin showed an excessive, very early expansion, followed by a dimensionally stable period, which cannot be explained at present. In the slag-based concretes, MgSO4 caused more expansion and visual damage than Na2SO4; however, the expansion limits defined in the respective standards were not exceeded. Both the ASTM C1293 and RILEM AAR-3.1 test methods for the determination of ASR expansion appear to give essentially reliable identification of expansion caused by highly reactive aggregates. Alkali-activated materials in combination with an unreactive or potentially expansive aggregate were in no case seen to cause larger expansions; only the aggregates of known very high reactivity were seen to be problematic. The results of freeze–thaw testing (with/without deicing salts) of alkali-activated concretes suggest an important influence of the curing conditions and experimental conditions on the test outcomes, which need to be understood before the tests can be reliably applied and interpreted.
Keywords: alkali-activated materials/geopolymers, sulphate resistance, alkali silica reactivity, freeze-thaw resistance, Rilem TC
Published in DiRROS: 17.08.2023; Views: 225; Downloads: 163
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