1. Stabilization of river dredged sediments by means of alkali activation technologyKarmen Fifer Bizjak, Lea Žibret, Mojca Božič, Boštjan Gregorc, Vilma Ducman, 2024, izvirni znanstveni članek Povzetek: Purpose
Alkali activation process has been applied to fresh river clay-rich sediments in order to increase their mechanical properties and make them suitable for soil stabilization.
Materials and methods
Dredged sediments were mixed with up to 30 mass percent (ma%) of fly ash (FA) or ladle slag (LS) and after curing for 3 days at 60 °C, the bending and compressive strength have been determined. The mixtures which exhibited the highest strengths were further optimized for being used in soil stabilization. For this purpose, the sediment was stabilized with 4 ma% of quicklime (QL) and after 1 h 30 ma% of FA with alkali activator was added and cured for 1, 7 and 28 days.
Results
The stabilized sediment has a significantely better geomechanical performance in comparison with the sediment alone. Stabilizing the dredged sediment using alkali activation technology provides high enough strengths to eventually make it suitable for anti-flood embankments.
Conclusions
The results confirmed the suitability of the investigated technology for soil stabilization. Ključne besede: river sediment, alkali activated materials, ladle slag, fly ash, mechanical strength, soil stabilization Objavljeno v DiRROS: 09.09.2024; Ogledov: 318; Prenosov: 4723 Celotno besedilo (1,41 MB) Gradivo ima več datotek! Več... |
2. Lightweight aggregates made from fly ash using the cold-bond process and their use in lightweight concreteAna Frankovič, Violeta Bokan-Bosiljkov, Vilma Ducman, 2017, izvirni znanstveni članek Povzetek: Aggregates made from fly ash have been developed by means of the cold-bonding process, with the addition of Portland cement as a binder at (10, 20, and 30) % of mass fractions, and by pouring the mixtures into moulds. After curing for 28 d the samples were processed into aggregate by crushing and sieving. An aggregate containing a weight percentage of 10 % of cement was additionally produced by pelletization on a granulating plate. The density, water-adsorption capacity, porosity, compressive strengths, and frost resistance of the samples were determined. The aggregates prepared by both routes were then used to make concrete samples, whose properties were then compared to those of conventional concrete made using limestone aggregate. The compressive strength of the concrete made with the granulated aggregate reached 16.0 MPa after 28 d, whereas that of the concrete made with crushed aggregate amounted to 24.1 MPa, and that of the conventional concrete was 34.6 MPa. Ključne besede: fly ash, lightweight aggregates, density, compressive strength, frost resistance Objavljeno v DiRROS: 14.08.2024; Ogledov: 371; Prenosov: 263 Celotno besedilo (1,65 MB) Gradivo ima več datotek! Več... |
3. Dehydration with microwave irradiationAnže Tesovnik, Barbara Horvat, 2024, zaključena znanstvena zbirka raziskovalnih podatkov Povzetek: The dataset supports the results shown in the tables and figures in the article entitled “Rapid immobilisation of chemical reactions in alkali-activated materials using solely microwave irradiation” (doi: https://doi.org/10.3390/min14121219). It contains measurements of mechanical and structural evaluation, as well as chemical and mineralogical analysis. Ključne besede: measurments, alkali-activated materials, geopolymers, slag, fly ash, rock wool, glass wool, metakaolin, microwave irradiation, dehydration, stopping of chemical reactions, efflorescence Objavljeno v DiRROS: 12.08.2024; Ogledov: 77; Prenosov: 11393 Raziskovalni podatki (4,87 MB) |
4. Potential solutions for ▫$CO_2▫$-capturing technologies in the slovenian contextJanvit Golob, Dušan Klinar, Mihael Bricelj, 2012, izvirni znanstveni članek Povzetek: Human activities have caused an enormous rise of the CO2 concentration in the Earth’s atmosphere over the past 200 years. In order to alleviate this problem, the threats to and the concerns of the international community need to be converted into economic opportunities for national economies, which shall develop and utilize technological opportunities rather than simply accepting international obligations to reduce CO2 emissions. In the article we analyze technological possibilities in the Slovenian context as possible opportunities for promoting sustainable development based on regional, renewable resources. Beginning with an analysis of the amine process for CO2 concentration and its possibilities, we continue with CO2 chemistry examples, like the precipitation of calcium carbonate from Ca++ sources like lime or fly ash. Through the concept of product engineering we emphasize the need for a stepwise realization from the laboratory to a pilot plant and then to the industrial scale. The growth of biomass through forestry or algae production can provide an additional CO2 sink. However, for an efficient technical solution and implementation a close working relationship between biologists and engineers is required. Ključne besede: CO2 minimization, technological opportunities, amine concentration, CO2 chemistry, forestry, algae production, fly ash CO2 absorption Objavljeno v DiRROS: 05.08.2024; Ogledov: 312; Prenosov: 226 Celotno besedilo (328,38 KB) Gradivo ima več datotek! Več... |
5. Adsorption efficiency of cadmium (II) by different alkali-activated materialsNataša Mladenović Nikolić, Ljiljana Kljajević, Snežana B. Nenadović, Jelena Potočnik, Sanja Knežević, Sabina Dolenec, Katarina Trivunac, 2024, izvirni znanstveni članek Povzetek: The objective of this study was to demonstrate the potential utilization of fly ash (FA), wood ash (WA), and metakaolin (MK) in developing new alkali-activated materials (AAMs) for the removal of cadmium ions from waste water. The synthesis of AAMs involved the dissolution of solid precursors, FA, WA, and MK, by a liquid activator (Na2SiO3 and NaOH). In concentrated solutions of the activator, the formation of an aluminosilicate gel structure occurred. DRIFT spectroscopy of the AAMs indicated main vibration bands between 1036 cm−1 and 996 cm−1, corresponding to Si-O-Si/Si-O-Al bands. Shifting vibration bands were seen at 1028 cm−1 to 1021 cm−1, indicating that the Si-O-Si/Si-O-Al bond is elongating, and the bond angle is decreasing. Based on the X-ray diffraction results, alkali-activated samples consist of an amorphous phase and residual mineral phases. The characteristic “hump” of an amorphous phase in the range from 20 to 40◦ 2θ was observed in FA and in all AWAFA samples. By the XRD patterns of the AAMs obtained by the activation of a solid three-component system, a new crystalline phase, gehlenite, was identified. The efficiency of AAMs in removing cadmium ions from aqueous solutions was tested under various conditions. The highest values of adsorption capacity, 64.76 mg/g (AWAFA6), 67.02 mg/g (AWAFAMK6), and 72.84 mg/gmg/g (AWAMK6), were obtained for materials activated with a 6 M NaOH solution in the alkali activator. The Langmuir adsorption isotherm and pseudo-second kinetic order provided the best fit for all investigated AAMs. Ključne besede: fly ash, metakaolin, wood ash, adsorption kinetics, cadmium (II) Objavljeno v DiRROS: 23.05.2024; Ogledov: 459; Prenosov: 342 Celotno besedilo (7,68 MB) Gradivo ima več datotek! Več... |
6. The use of paper industry side product in constructionBarbara Likar, Laura Vovčko, 2020, objavljeni znanstveni prispevek na konferenci Povzetek: The amount of waste material and side products of various industrial plants is increasing, which leads into waste accumulation and lack of space in disposal landfills. Paper industry, with its side products paper sludge and ash, faces these same issues. To reduce the accumulation of these materials, we explored the possibility of their use in construction. At first a series of geomechanical tests was conducted on a product consisting of fly ash and bottom ash. Based on the laboratory results test fields were constructed, where the preparation and installation technologies were tested. The fields were exposed to the atmospheric conditions, so durability of the product in the natural environment was proven. Since the composition of both fly ash and bottom ash depends on the paper industry process, a continuous monitoring of their characteristics was established. Ključne besede: paper industry, fly ash, bottom ash, construction material, geomechanical properties Objavljeno v DiRROS: 05.03.2024; Ogledov: 544; Prenosov: 241 Celotno besedilo (521,45 KB) Gradivo ima več datotek! Več... |
7. 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: 573; Prenosov: 369 Celotno besedilo (14,96 MB) Gradivo ima več datotek! Več... |
8. 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: 606; Prenosov: 297 Celotno besedilo (1,05 MB) Gradivo ima več datotek! Več... |
9. 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: 740; Prenosov: 348 Celotno besedilo (2,01 MB) Gradivo ima več datotek! Več... |
10. Characterizing the interfacial zones of fly ash based alkali activated adhesives to various substratesWolfgang Wisniewski, Vilma Ducman, 2022, izvirni znanstveni članek Povzetek: Alkali Activated Materials (AAMs) are important potential substitutes for cement in many materials. The AAMs presented here are based on industrial ground granulated blast furnace slag (GGBFS) and fly ash (FA). They are tested for their suitability as adhesives for joining concrete, ceramic tiles, a wood-based geopolymer (WGP) and a high density geopolymer (HDGP). After mixing multiple batches and performing preliminary tests of the resulting shrinkage, bending-, compressive- and pull-of-strengths to standard ceramic tiles, selected mixtures are tested for their open time and applied to bond intended substrates. The interfacial zones (ITZ) of an AAM containing additional KOH and the most comparable KOH-free AAM to concrete, ceramic tiles, WPG and HDGP are subsequently characterized in detail using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS). Both mechanical interlocking and areas of probable chemical bonding are identified. Ključne besede: adhisive, fly ash, ITZ, pull of test, open ccess Objavljeno v DiRROS: 21.06.2023; Ogledov: 676; Prenosov: 401 Celotno besedilo (4,51 MB) Gradivo ima več datotek! Več... |