1,720,958 research outputs found
Utilization and Reactivity Enhancement of Wood Ash in Cement–Based and Alkali–Activated Materials
No full textConcrete is the most widely used construction material worldwide due to its good mechanical properties, durability, and affordability. However, Portland cement production contributes approximately 5–8% of global anthropogenic CO₂ emissions. Supplementary cementitious materials (SCM), which can partially replace Portland cement, present the greatest potential for reducing the environmental impact of the construction industry. Recently, there has been increasing interest in research on the potential use of wood ash (WA) as an SCM. Utilization of WA in concrete promotes waste reuse and offers a sustainable option for SCM. However, since the characteristics of WA can vary significantly depending on its source and production conditions, further research is needed to optimize its effective use. This study aims to investigate the potential use of WA as an SCM and compare it with coal fly ash (FA), focusing on enhancing its reactivity and performance in both cement-based and alkali-activated materials through mechanochemical activation (MCA; high-energy grinding). The properties of WAs and the effect of MCA were examined, including Strength Activity Index (SAI), Frattini, R3 test, TGA/DTG, XRD and SEM-EDS analysis. WA was used to replace 10 wt.% and 20 wt.% of Portland cement in concrete and of ground granulated blast furnace slag (GGBFS) in alkali-activated mortars. Workability, strength, hydration behaviour, and microstructural properties were evaluated. The leaching behavior of WA was evaluated through batch tests, and the environmental performance of selected concrete mixes containing WA was further investigated using dynamic surface leaching tests (DSLT) on monolithic concretes. The frost durability of these concrete mixes was examined using the de-icing salt frost scaling test. MCA significantly increased the fineness and specific surface area of WA significantly, resulting in enhanced reactivity. Depending on their chemical composition, some WAs exhibited predominantly pozzolanic behavior, while others showed latent hydraulic properties. The use of WA after MCA in concrete and alkali-activated mortars led to improvements in strength, cumulative heat release and microstructure compared to unground WA. At lower replacement levels, the compressive strength improved compared with the control sample in certain mixes. In air-entrained concrete, it improves frost durability by reducing surface scaling. MCA improved the environmental compatibility by reducing the leaching of most heavy metals, despite stainless-steel grinding media increasing Cr and Ni concentrations. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that, after MCA, WAs with higher pozzolanic oxide contents clustered more closely with FA
Utilization and Reactivity Enhancement of Wood Ash in Cement–Based and Alkali–Activated Materials
No full textConcrete is the most widely used construction material worldwide due to its good mechanical properties, durability, and affordability. However, Portland cement production contributes approximately 5–8% of global anthropogenic CO₂ emissions. Supplementary cementitious materials (SCM), which can partially replace Portland cement, present the greatest potential for reducing the environmental impact of the construction industry. Recently, there has been increasing interest in research on the potential use of wood ash (WA) as an SCM. Utilization of WA in concrete promotes waste reuse and offers a sustainable option for SCM. However, since the characteristics of WA can vary significantly depending on its source and production conditions, further research is needed to optimize its effective use. This study aims to investigate the potential use of WA as an SCM and compare it with coal fly ash (FA), focusing on enhancing its reactivity and performance in both cement-based and alkali-activated materials through mechanochemical activation (MCA; high-energy grinding). The properties of WAs and the effect of MCA were examined, including Strength Activity Index (SAI), Frattini, R3 test, TGA/DTG, XRD and SEM-EDS analysis. WA was used to replace 10 wt.% and 20 wt.% of Portland cement in concrete and of ground granulated blast furnace slag (GGBFS) in alkali-activated mortars. Workability, strength, hydration behaviour, and microstructural properties were evaluated. The leaching behavior of WA was evaluated through batch tests, and the environmental performance of selected concrete mixes containing WA was further investigated using dynamic surface leaching tests (DSLT) on monolithic concretes. The frost durability of these concrete mixes was examined using the de-icing salt frost scaling test. MCA significantly increased the fineness and specific surface area of WA significantly, resulting in enhanced reactivity. Depending on their chemical composition, some WAs exhibited predominantly pozzolanic behavior, while others showed latent hydraulic properties. The use of WA after MCA in concrete and alkali-activated mortars led to improvements in strength, cumulative heat release and microstructure compared to unground WA. At lower replacement levels, the compressive strength improved compared with the control sample in certain mixes. In air-entrained concrete, it improves frost durability by reducing surface scaling. MCA improved the environmental compatibility by reducing the leaching of most heavy metals, despite stainless-steel grinding media increasing Cr and Ni concentrations. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that, after MCA, WAs with higher pozzolanic oxide contents clustered more closely with FA
The Effects of Partial Replacement of Ground Granulated Blast Furnace Slag by Ground Wood Ash on Alkali-Activated Binder Systems
No full textCement production contributes significantly to carbon dioxide emissions. Alkali-activated materials offer an environmentally friendly alternative due to their comparable strength, durability and low-carbon emissions while utilizing wastes and industrial by-products. Wood ash is a waste material that shows promising results as a partial replacement for Portland cement and precursors in alkali-activated systems. The aim of this study was to examine the effect of ground wood ash on the mechanical properties of alkali-activated mortars. Wood ash was incorporated as a 0 wt%, 10 wt% and 20 wt% partial replacement for ground granulated blast furnace slag (GGBFS). The wood ashes were ground in a planetary ball mill for 10 and 20 min. Sodium silicate (Na2SiO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH) were used as alkali activators. The results demonstrated that ground wood ash improved the mechanical properties of alkali-activated systems compared to untreated wood ash. However, the incorporation of wood ash increased the porosity of the binder matrix.Validerad;2023;Nivå 2;2023-08-21 (hanlid);Funder: Skanska</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Ground wood ash as a supplementary cementitious material: Effects on strength, durability and environmental performance of concrete
No full textThis study investigates the use of wood ash (WA3 and WA4), both unground and ground for 10 and 20 min, as a partial replacement for Portland cement in concrete. Fly ash (FA) is used as a reference. The effects of incorporating ground and unground wood ash on fresh and hardened properties, hydration behavior, microstructure, durability, and environmental performance were evaluated. Grinding wood ash significantly improved the compressive strength of concrete and increased the cumulative heat release during hydration. Air-entraining admixtures significantly improved the freeze-thaw resistance of concrete with ground wood ash and reduced surface scaling compared to unground ash. Furthermore, grinding reduced the mobility of key heavy metals, enhancing environmental compatibility. Overall, 10-minute grinding provided the optimal balance between performance and environmental safety. These results support the controlled use of ground wood ash as a sustainable supplementary cementitious material in concrete, contributing to both concrete performance and environmental benefits.Validerad;2025;Nivå 2;2025-11-26 (u8);Funder: Skanska;Full text license: CC BY;This article has previously appeared as a manuscript in a thesis.</p
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
