11. Heavy metal signature and environmental assessment of nearshore sediments: Port of Koper (Northern Adriatic Sea)Nastja Rogan Šmuc, Matej Dolenec, Sabina Dolenec, Ana Mladenovič, 2018, izvirni znanstveni članek Povzetek: Heavy metal abundance and potential environmental risks are reported for surface sediments (n = 21) from the Port of Koper area, Republic of Slovenia. The enrichment factor (EF) indicates minor enrichment in arsenic (As), cadmium (Cd), copper (Cu), molybdenum (Mo), lead (Pb), antimony (Sb), and zinc (Zn), moderately to severely enriched with nickel (Ni). The trace metal chemistries, in the context of sediment quality guidelines (SQG), imply adverse threshold effect concentrations (TEC) and probable effect concentrations (PEC), for Ni only. Sediment sequential leaching experiments demonstrated that the majority of heavy metals were of natural lithogenic origin and low bioavailability. The heavy metals’ potential for “Risk Assessment Code” values exhibited no or low anthropogenic environmental burden, with the exception of Mo.
Ključne besede: port sediments, heavy metals, chemical speciation, risk assessment, Northem Adriatic Sea
Objavljeno v DiRROS: 12.12.2023; Ogledov: 203; Prenosov: 112
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12. Evaluation of ash pozzolanic activity by means of the strength activity index test, frattini test and DTA/TG analysisSabina Dolenec, Vilma Ducman, 2018, izvirni znanstveni članek Povzetek: The pozzolanic activity of five different types of ash was studied using various direct and indirect methods. In addition to strength activity index (SAI) determination and the Frattini test, ash pozzolanicity was assessed via differential thermal and thermogravimetric analyses (DTA/TG) after curing for 7, 28 and 90 days. The results showed that, due to their respective mineralogical, chemical and physical characteristics, the ashes exhibited different levels of pozzolanic activity in terms of the amount of lime with which they could chemically bind, as well as reaction kinetics. Although SAI and Frattini test results were not in agreement in the case of some of the ashes, DTA/TG analysis revealed that a certain amount of portlandite was consumed, thus confirming the occurrence of a pozzolanic reaction. The results also showed that ashes with higher amounts of reactive SiO2 were more reactive, while those with higher BET surface areas displayed a faster pozzolanic reaction rate.
Ključne besede: biomass ash, DTA/TG, fly ash, Frattini test, pozzolanic activity, SAI
Objavljeno v DiRROS: 11.12.2023; Ogledov: 218; Prenosov: 106
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13. Experimental study and thermodynamic modelling of the temperature effect on the hydration of belite-ye’elimite-ferrite cementsMaruša Mrak, Frank Winnefeld, Barbara Lothenbach, Andraž Legat, Sabina Dolenec, 2024, izvirni znanstveni članek Povzetek: This study focuses on the kinetics of hydration, phase assemblage, microstructure and mechanical properties after various hydration times of two different BCSA cements at 5, 20, 40 and 60 ◦C and compares experimental data with thermodynamic modelling. Different curing temperatures change the type of hydrates and their amounts. Ye’elimite and gypsum in belite-ye’elimite-ferrite cements are almost fully reacted after 24 h of hydration at 20, 40 and 60 ◦C, while not at 5 ◦C. The hydration of belite is slower than the one of ye’elimite, but reaches a high degree of hydration after 150 days which is increasing with temperature. Less ettringite is present at elevated temperatures due to its increasing solubility, while more monosulfate is observed. Furthermore, with increasing temperature siliceous hydrogarnet forms at the expenses of strätlingite as well as more C S H is found as more belite reacts resulting in higher compressive strength. Dense and homogenous microstructure is observed at 5 ◦C, while it is more heterogeneous at higher temperatures. The presence of more ye’elimite resulted in higher ettringite and str¨atlingite formation and a higher compressive strength, while more belite yields more C S H in the hydrates and lower compressive strength.
Ključne besede: belite-ye’elimite-ferrite cement, temperature, hydration, thermodynamic modelling
Objavljeno v DiRROS: 11.12.2023; Ogledov: 175; Prenosov: 147
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14. Efficiency of novel photocatalytic coating and consolidants for protection of valuable mineral substratesAndreja Pondelak, Sabina Dolenec, Jonjaua Ranogajec, Luka Škrlep, Snezana B. Vučetić, Vilma Ducman, Andrijana Sever Škapin, 2019, izvirni znanstveni članek Povzetek: In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO2/ZnAl layered double hydroxide (LDH) coating and silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection and consolidation of four porous mineral substrates: brick, stone, render and mortar. The photocatalytic efficiency of TiO2/ZnAl LDH coating, as well as consolidation efficiency of two consolidants, both applied on model substrates, were studied. The photocatalytic coating showed significant activity and performed well after the durability tests involving rinsing and freezing/thawing procedures. After treatment with both consolidants, a serious enhancement of consolidation of the used substrates was found. On the other hand, the application of TiO2/ZnAl LDH, as well as consolidants, caused negligible changes in the water vapour permeability values and in appearance of the porous mineral substrates, indicating a high level of compatibility.
Ključne besede: photocatalytic coating, consolidant, protection, conservation, porous substrate, cultural heritage
Objavljeno v DiRROS: 21.11.2023; Ogledov: 252; Prenosov: 180
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15. Use of fly ash and phosphogypsum for the synthesis of belite-sulfoaluminate clinkerSabina Dolenec, Lea Žibret, Emilija Fidanchevska, V. Jovanov, Biljana Angjusheva, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: Fly ash and phosphogypsum were used as Naturally Occurring Radioactive Materials (NORM) by-products for the synthesis of belite-sulfoaluminate clinkers. The influence of raw mixture composition and firing temperature was investigated. Clinkers and cements were examined by X-ray powder diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. The compressive strength of the cements was determined after 28 days. Clinker phases identified included ye’elimite, ß-phase of belite, ternesite and gehlenite, while the main hydration product of the cement pastes was ettringite. The results showed that belite-sulfoaluminate cements can be fabricated with a compressive strength of 45.9 N/mm2 by firing the raw mixture (70 wt.% marl, 10 wt.% bauxite and 20 wt.% phosphogypsum) at a temperature of 1320°C/1h.
Ključne besede: clinker, microstructure, fly ash, gypsum, calcium sulphoaluminate
Objavljeno v DiRROS: 27.10.2023; Ogledov: 396; Prenosov: 155
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16. A Raman microspectroscopy-based comparison of pigments applied in two gothic wall paintings in SloveniaMaja Gutman, Ajda Mladenovič, Anabelle Križnar, Sabina Dolenec, 2019, izvirni znanstveni članek Povzetek: The present study deals with the characterisation of pigments used in two overlaid gothic wall paintings from the former 13th century Minorite church of St. Francis of Assisi (Koper, Slovenia), in order to define differences in the technologies used. Paint layer samples were analysed via Raman microspectroscopy, supported by SEM/EDS and FTIR analysis, when necessary. The results revealed that the 14th century mural was painted mainly a fresco with final elements a secco, a technique typical of Italian mediaeval wall painting. In contrast, the 15th century painting was executed mostly a secco, a technique often applied in Northern Europe and the Alpine region. The differences between the two paintings are especially obvious in the pigments applied. While the earlier painting is characterised by azurite, carbon black, red and yellow ochres, lime white and green earth, the palette used for the younger painting is much broader. In addition to red and yellow ochres, carbon black and lime white, lead pigments such as lead white, red lead and lead-tin yellow type I were also determined, as well as a number of expensive pigments including cinnabar, azurite and malachite. Also found in the younger painting was the rare orange yellow pigment vanadinite. In both layers, azurite was applied a secco for the background area. Gilding was confirmed in both layers, carried out as application of gold leaves on red bole (in the earlier mural) and on mordant (on a younger, superimposed (overlaid painting), which is quite exclusive and rare for Slovene mediaeval painting. In the younger layer also a use of tin foil for secondary elements was discovered.
Ključne besede: wall paintings, pigments, Gothic, golding, Raman microspectroscopy
Objavljeno v DiRROS: 27.10.2023; Ogledov: 401; Prenosov: 165
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17. Characterisation of 20th century cementitious materials from selected cultural heritage structures in SloveniaMateja Golež, Vesna Zalar Serjun, Mateja Štefančič, Darja Rant, Sabina Dolenec, 2023, izvirni znanstveni članek Povzetek: This paper deals with the characterisation of cementitious materials from selected cultural heritage structures in Slovenia. The mineralogical–petrographic compositions of an aggregate, a type of binder and secondary minerals were studied via electron microscopy and X-ray powder diffraction. The porosity and pore network were determined using a mercury porosimeter. The results show that the aggregate of the samples was highly diverse, ranging from limestone, dolomite, quartz, feldspar and mica. The binder of the investigated samples was cementitious; either ordinary Portland cement was used, or ordinary Portland cement blended with ground granulated blast furnace slag was used. Some samples consisted of cement–lime binders. The investigated examples entailing cement materials for their construction contribute to a better understanding of the technology used to prepare historical cementitious and cement–lime mixtures.
Ključne besede: 20th century, cementitious materials, historical concrete, cultural heritage
Objavljeno v DiRROS: 15.09.2023; Ogledov: 289; Prenosov: 179
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18. Up-scaling and performance assessment of façade panels produced from construction and demolition waste using alkali activation technologyAna Frankovič, Vilma Ducman, Sabina Dolenec, Matteo Panizza, Sergio Tamburini, Marco Natali, Katherine-Maria Pappas, Constantinos Tsoutis, Adriana Bernardi, 2020, izvirni znanstveni članek Povzetek: Novel prefabricated insulating façade panels were developed from construction and demolition waste (CDW) aggregates under the framework of the European H2020 project InnoWEE. These non-structural components, aimed at improving the thermal efficiency of existing buildings, consist of an insulating plate covered by a facing layer made of CDW aggregates bound with metakaolin, furnace slag and class F fly ash activated by a potassium silicate solution. The paper presents the design and assessment of the binder and panels for exterior use, taking into account mechanical performance, behaviour in the presence of water and durability issues. Testing was carried out on both laboratory prototypes and panels from the pilot industrial production.
Ključne besede: construction and demolition waste, alkali activated materials, geopolymers, properties, up-scalimg
Objavljeno v DiRROS: 21.08.2023; Ogledov: 283; Prenosov: 158
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19. 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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: alkali-activated materials/geopolymers, sulphate resistance, alkali silica reactivity, freeze-thaw resistance, Rilem TC
Objavljeno v DiRROS: 17.08.2023; Ogledov: 240; Prenosov: 173
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20. Effects of the temperature on the pore evolution during sintering of the belite-sulfoaluminate cement clinker using x-ray computed microtomographySabina Dolenec, Lidija Korat, Maruša Mrak, Andrej Ipavec, Lea Žibret, 2020, izvirni znanstveni članek Povzetek: In this paper, the effects of the sintering temperature on the pore evolution of the belite-sulfoaluminate cement clinker were evaluated. Belite-sulfoaluminate cement clinker with a targeted composition of 65 w/% b-belite, 20 w/% calcium sulfoaluminate and 10 w/% ferrite was sintered at three different temperatures: 1200 °C, 1250 °C and 1300 °C. To quantitatively evaluate the pore evolution during sintering, a 3D microstructure reconstruction by micro-CT was used. From the data, the pore volume frac- tion and pore number were extracted and compared, and the pore size distribution with the sintering temperature was obtained as well. Additionally, the pore shape and distribution were displayed in 3D based on actual microstructure data. Clinker samples were also characterized by Hg-intrusion porosimetry and gas sorption. The changes in the pore evolution occurred to a larger extent when sintering at 1300 °C. Apart from a significant porosity decrease, pore coarsening was evident at this temperature, reducing their connectivity and shrinkage of the clinker. Simultaneously, the bulk and apparent densities increased with the temperature due to densification, while the BET surface area of the studied clinkers decreased, indicating the rounding of pores and particle coalescence with an increasing grain growth.
Ključne besede: klinker, belit-sulfoaluminat, razvoj por, sintranje
Objavljeno v DiRROS: 04.08.2023; Ogledov: 343; Prenosov: 146
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