Luleå University of Technology Publications
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The effect of real curing temperatures on early age concrete strength development in massive concrete structures
No full textAt the early maturity stage, the curing temperature has a significant impact on the mechanical properties of concrete. Concrete cubes are cured in water baths at different temperatures—5 °C, 20 °C, 35 °C, and 50 °C—in order to measure their compressive strength. This method is predicated on the knowledge that the pace of cement hydration is strongly influenced by the curing temperature. Then, the realistic curing temperature regime was imposed where the temperature of the curing water was modified based on the temperature patterns obtained from semi-adiabatic testing of concrete mixes to simulate curing conditions in the core of massive concrete structures. Ordinary Concrete: Compared to specimens cured at an isothermal curing at 20 °C, those cured in water baths at realistic curing showed an increase in compressive strength of 48% at seven days and 18.5% at 28 days. Fly Ash 18% Replacement: Compared to specimens cured at at 20 °C, the compressive strength of those cured at realistic curing increased by 45% at seven days, with a modest rise of 0.2% by the 28th day. Slag 18% Replacement: Compared to specimens cured at 20 °C, the compressive strength of those cured at realistic curing increased significantly by 121% at seven days and by 21.7% at 28 days.Validerad;2025;Nivå 2;2025-06-30 (u2);Full text license: CC BY 4.0;</p
Gender in industrial mine work and organizations – recommended actions toward gender equality
No full textQuestions of how the mining industry can address gender imbalance and inequality are recurring and increasing across the sector. Neglecting how gender affects organizational processes, work environment and work, risks reproducing, rather than transforming the organizational culture and processes that uphold masculine culture and male domination in the industry. The aim of the article is to give research-based suggestions to the industry - companies and policy-makers - on how the results of gender perspectives in research on mining organizations can contribute to inclusive and innovative work environments, organizational cultures and processes in mining. Based on an extensive review of previous research on gender in mining, the study concludes that possible transformative change, through new technology and new forms of organization, may enable organizations to shift the gendered structure of mining. A shift toward automated mines and increase of industrial mining due to the demands of the green transition will lead to new types of jobs and new forms of organizing mining work. Within these changes lies a possibility to transform gendered structures in mining.Validerad;2025;Nivå 1;2025-11-06 (u2);Fulltext license: CC BY</p
Industrial circular ecosystem entrant: examining small firms
No full textPurpose: This study serves a dual purpose. First, it aims to explore the phase-wise progression that small and medium-sized enterprises (SMEs) and startups must undertake to become successful ecosystem partners, supporting large industrial firms in their circular transition. Second, it seeks to examine how these small firms manage change and foster collaborative cultures through strategies enabled by positive organizational scholarship (POS) during their phased evolution. Design/methodology/approach: This study provides empirical evidence through a multiple case study-based approach involving 12 born-circular SMEs/startups from 5 diverse Indian industrial sectors. Insights were gathered by conducting two rounds of semi-structured interviews with 24 participants and one validatory seminar with eight participants. Findings: This research identified three distinct and complementary phases – compare, compete and collaborate – that SMEs/startups can undergo to emerge as successful ecosystem partners. Each phase encompasses specific business practices, including various circular activities. These activities serve as clear indicators of the smaller firms’ potential competence in aiding larger firms during their circular transitions. Originality/value: This paper contributes to the theoretical understanding of the circular economy by outlining a trajectory for SMEs/startups to establish successful partnerships. Another contribution is the application of POS as a positive change management paradigm to facilitate circularity. Additionally, the study highlights the context of developing nations, which remain underexplored compared to their developed counterparts in circularity initiatives.Validerad;2025;Nivå 2;2025-03-12 (u2);Full text license: CC BY</p
Adsorption of gases in acetate functionalized silica: Experimental and Monte Carlo molecular simulation study
No full textAdsorption of carbon dioxide and other gases on a novel acetate functionalized silica adsorbent under various conditions is investigated experimentally and theoretically by grand-canonical Monte Carlo (GCMC) simulations. The acetate functional group has the capability to interact with the carbon atoms in CO2 molecules due to the electron-donating properties of the carbonyl and ether groups. However, the acetate functional group has not yet been examined for CO2 adsorption on silica. Adsorption of CO2, CH4, N2, and H2 was measured experimentally in the temperature range of 253–373 K and pressure range of 0–100 kPa. CO2 showed significantly higher adsorption compared to other gases with maximum adsorption of ca. 32 cc/gr at standard condition (STP) at a pressure of 100 kPa and a temperature of 253 K. The recorded adsorption data could be fitted by Freundlich isotherms, indicating heterogeneous adsorption sites. To better understand the heterogeneous adsorption sites, GCMC simulations were used to examine the effects of pore size, temperature, pressure, concentration of functional groups in the silica matrix, and competitive adsorption. The GCMC data was in good agreement with the experimental data and suggested the oxygen-containing moieties (i.e., carbonyl and ether groups) on the acetate group as the adsorption sites. These sites displayed high Lewis acid-base interaction with the CO2 molecules. The GCMC data indicated selective adsorption of CO2 over N2 and a CO2/N2 binary gas mixture selectivity of 20 for a 10/90 CO2/N2 feed. To the best of our knowledge, this is the first report on the experimental adsorption of CO2 over acetate functionalized silica adsorbent coupled with an investigation of the adsorption sites through GCMC simulations.Validerad;2025;Nivå 2;2025-03-12 (u5);Full text license: CC BY</p
Modelling of ductile fracture considering the effect of stress triaxiality and the energy partition theory in thin high-strength steel sheets
No full textIt is well recognized in the literature that the fracture process of thin metal sheets involves three energy dissipation mechanisms i.e., plasticity, necking and surface separation. However, the complex stress state in thin structures hinders the experimental assessment of these quantities and, consequently, the failure modelling. This work evaluates the contribution of these mechanisms to the ductile damage of a thin advanced high strength steel sheet under different stress triaxiality ranges. The essential work of fracture test was carried out on a set of different notch geometry specimens that cover a wide range of stress states. The experimental trend of these specimens was simulated in ABAQUS/Explicit using a VUSDFLD subroutine. Bai and Wierzbicki uncoupled fracture model, which is a function of fracture plastic strain to stress triaxiality (η) and normalized Lode angle (, was selected as damage initiation criterion. A quantitative relationship of the fracture energy (G0) as a function of (η) was proposed in this work and implemented in the model as a damage evolution law. The model captures well the experimental response and the influence of (η) on the softening behavior of the material. It was found that the sensitivity of G0 to η is significant between 0.7 and 1.5. Above this rage, it seems that (η) has no influence on G0. The model showed also the relationship between the two local damage parameters (G0) and the necking (Gn) with respect to the stress state. G0 represents less than 10% of the total work of fracture, while the largest contribution comes from (Gn).Validerad;2025;Nivå 2;2025-03-12 (u4);Full text license: CC BY</p
Beyond communication services in future networks: 6G-enabled driving assistance through localization and sensing
No full textIntegrated Sensing and Communication (ISAC) is a promising enabler for the next generation of networks, allowing to utilize the same network infrastructure to perform both communication and radar-like functionality. The aim of this thesis is to investigate how sensing in 6G can be used for intelligent transportation use cases, potentially improving the sustainability and safety awareness of transportation systems. The study includes, among others, performance requirements analysis of sensing signal, building a sensing service model, and analyzing contradicting requirements for communication and sensing. There is no support for sensing in 5G, but is it safe to assume that 6G is going to be built on top of the existing 5G frame structure. Therefore, simulation tests were performed in millimeter wave (mmWave) frequencies based on an OFDM waveform and a frame structure similar to 5G with integrated sensing capabilities. The results also showcased potential performance of sensing in terms of positioning error and detection rate and their dependency on input parameters and channel noise. The studied scenario for sensing in urban environment indicates that enabling sub-meter resolution sensing in a 26 GHz channel can take up to 300 MHz of bandwidth with 0.1s refresh rate. The results also showcased less than 0.5% resource overhead for single target sensing.
Determination of the Critical Voltage for the Observation of Uncoated Wood Samples in Electron Microscopy
No full textElectron microscopy (EM) is a key tool for studying the microstructure of wood; however, observing uncoated samples poses a challenge due to surface charging. This study aims to identify the critical voltage that allows for the effective observation of uncoated wood samples without significant loading. As part of the experiment, samples of different wood species were tested, including Acacia (Robinia pseudoacacia L.), Oak (Quercus robur L.), Maple (Acer pseudoplatanus spp.), Ash (Fraxinus excelsior L.), Spruce (Picea abies (L.) Karst.), Thermowood (Thermal modifed Spruce), Garapa (Apuleia leiocarpa), Ipé (Handroanthus spp.), Merbau (Intsia bijuga), and Massaranduba (Manilkara spp.). Several methods were tested for surface preparation for SEM analysis, including the use of a circular saw, a hand milling machine, and a microtome. The results show that the optimal voltage for observing uncoated wood samples varied depending on the wood species. Regarding the selection of wood species and the results obtained, it was found that uncoated samples could be effectively observed. This finding suggests that practical observations can be accelerated and more cost-effective, as all wood species exhibited the required voltage range of 1 kV to 1.6 kV. Additionally, it was determined that using a secondary electron detector was optimal for such observations, as it provided a sufficiently strong signal even at relatively low voltages. Conversely, when using a backscattered electron detector, it was more beneficial to use coated samples to achieve a sufficient signal at higher voltages. This study brings new knowledge that will facilitate further research and applications of electron microscopy in the study of other wood species or wood-based materials.Validerad;2025;Nivå 2;2025-03-17 (u8);Full text license: CC BY;Funder: project IGA A_02_24 (Development and analysis of thermal insulation material based on foamed wood);</p
Developing non-aqueous slurry for CO2 capture
No full textThe urgency of mitigating CO2 emissions has become increasingly critical due to their detrimental effects on environmental sustainability and human health. Among emerging solutions, deep eutectic solvents (DESs) have garnered attention for their high CO2 capture capacities. However, widespread application of DESs has been constrained by their inherent high viscosity and cost. To overcome these limitations, this study further explores the novel strategy, where cosolvent addition and immobilization are combined to develop a non-aqueous slurry for CO2 capture with high efficiency. Here, [MEACl][EDA] with (1:5) molar ratio is mixed with ethylene glycol (EG) to form a non-aqueous DES solution, and the DES is further immobilized into the mesoporous silica to form a composite and then mixed with the DES-EG solution to make a slurry. The CO2 capture tests demonstrated 15 wt.% capture capacity at 22 °C and 1 bar, and efficient sorption and desorption rates (0.34 and 0.38 mol CO2/(kg sorbent·min) within the initial 2 min). The slurry also exhibited promising cyclic performance with 96.4 % recovery together with minimal solvent loss of 0.97 % and almost intact structure after 120 hr of heating at 110 °C. The improved capture capacity and kinetics, especially for desorption, as well as enhanced thermal stability of the non-aqueous system highlight its potential for industrial applications.Validerad;2025;Nivå 1;2025-03-18 (u8);Full text license: CC BY</p
Optimization of Thermoelectric Performance in p-Type SnSe Crystals Through Localized Lattice Distortions and Band Convergence
No full textCrystalline thermoelectric materials, especially SnSe crystals, have emerged as promising candidates for power generation and electronic cooling. In this study, significant enhancement in ZT is achieved through the combined effects of lattice distortions and band convergence in multiple electronic valence bands. Density functional theory (DFT) calculations demonstrate that cation vacancies together with Pb substitutional doping promote the band convergence and increase the density of states (DOS) near the Fermi surface of SnSe, leading to a notable increase in the Seebeck coefficient (S). The complex defects formed by Sn vacancies and Pb doping not only boost the Seebeck coefficient but also optimize carrier concentration (nH) and enhance electrical conductivity (σ), resulting in a higher power factor (PF). Furthermore, the localized lattice distortions induced by these defects increase phonon scattering, significantly reducing lattice thermal conductivity (κlat) to as low as 0.29 W m−1 K−1at 773 K in Sn0.92Pb0.03Se. Consequently, these synergistic effects on phonon and electron transport contribute to a high ZT of 1.8. This study provides a framework for rational design of high-performance thermoelectric materials based on first-principles insights and experimental validation.Validerad;2025;Nivå 2;2025-03-19 (u2);Full text license: CC BY 4.0;Funder: National Natural Science Foundationof China (52372210, 52072248); Guangdong Basicand Applied Basic Research Foundation (2023A1515010122, 2021A1515012128)</p
Navigating Digital Servitization for the Twin Transition: How Manufacturers Can Support Customers With Digitalization and Sustainability
No full textAs industrial sustainability concerns mount, manufacturers engaged in digital servitization grapple with the twin transition of configuring and implementing digital solutions to meet their customers' sustainability objectives. To address this challenge, a socio-technical systems theory-based framework is proposed. Drawing on case studies with three manufacturers undertaking digital servitization and on the sustainability, digital servitization, and socio-technical systems theory research, our framework highlights key processes in navigating the twin transition. It emphasizes the importance of contextual factors in defining a customer twin-transition roadmap, outlines key steps in reconfiguring technical and social subsystems, and stresses the joint optimization processes based on feedback and metrics. This systematic approach guides manufacturers in supporting their customers through the twin transition, emphasizing socio-technical systems and iterative processes for sustained success. Our findings contribute to the growing digital servitization and sustainability research by conceptualizing underlying processes in the twin transition and offering manufacturers practical insights. Validerad;2025;Nivå 2;2025-08-07 (u4);Full text: CC BY license;Funder: The Research Council of Norway</p