bluuebunny/crossref_metadata_2025 huggingface dataset:
Responding to COVID‐19: How group model building can assist the health and well‐being of urban Indigenous communities in Australia
Authors: Fredericks Bronwyn , Bradfield Abraham , McAvoy Sue , Ward James , Spierings Shea , Combo Troy , Toth‐Peter Agnes
Published: December 2023

In this paper, we discuss a rapid‐fire study involving Indigenous and non‐Indigenous stakeholders from the urban Indigenous health sector who collaborated to produce an “Urban COVID‐19 Systems Map.” The map outlines the behaviours, actions and responses that stakeholders identified as mitigating or exacerbating COVID‐19 risks in urban Indigenous communities. Data were collected and analysed during the height of the pandemic in 2021. We begin by introducing the characteristics of system thinking—the methodology that informed our research—and consider its use in Indigenous health research more broadly. We then outline our utilisation of system thinking and discuss how it was applied to the three workshops. System thinking contributes to collaboration and collective debate amongst stakeholders and aims to produce holistic understandings of complex problems, such as pandemics. This article provides a reflective overview of the benefits and challenges of applying system thinking in Indigenous health research whilst also sharing some of the research findings. We argue that centralising the voices of stakeholders, particularly Indigenous stakeholders, is critical to developing and implementing effective and culturally appropriate responses to pandemics and is equally as important to the preparedness for future pandemics.
Molecular Dynamic Simulations of Aqueous Micellar Organometallic Catalysis: Methane Functionalization as a Case Study
Authors: Matamoros‐Recio Alejandra , Alonso‐Rueda Elia , Borrego Elena , Caballero Ana , Pérez Pedro J. , Martín‐Santamaría Sonsoles
Published: December 2023

Molecular Dynamics (MD) simulations constitute a powerful tool that provides a 3D perspective of the dynamical behavior of chemical systems. Herein the first MD study of the dynamics of a catalytic organometallic system, in micellar media, is presented. The challenging methane catalytic functionalization into ethyl propionate through a silver‐catalyzed process has been targeted as the case study. The intimate nature of the micelles formed with the surfactants sodium dodecylsulfate (SDS) and potassium perfluorooctane sulfonate (PFOS) has been ascertained, as well as the relative distribution of the main actors in this transformation, namely methane, the diazo reagent and the silver catalyst, the latter in two different forms: the initial compound and a silver‐carbene intermediate. Catalyst deactivation occurs with halide containing surfactants dodecyltrimethylammonium chloride (DTAC) and Triton X‐100. Computed simulations allow explaining the experimental results, indicating that micelles behave differently regarding the degree of accumulation and the local distribution of the reactants and their effect in the molecular collisions leading to net reaction.
Seed‐Mediated Growth for High‐Efficiency Perovskite Solar Cells: The Important Role of Seed Surface
Authors: Hu Yiqi , Zhong Qixuan , Song Bin , Xu Hongyu , Li Qiuyang , Li Shunde , Qiu Yinghua , Yang Xiaoyu , Chen Jinxing , Zhang Qiao , Zhu Rui , Cao Muhan
Published: December 2023

Additive engineering has emerged as one of the most promising strategies to improve the performance of perovskite solar cells (PSCs). Among additives, perovskite nanocrystals (NCs) have a similar chemical composition and matched lattice structure with the perovskite matrix, which can effectively enhance the efficiency and stability of PSCs. However, relevant studies remain limited, and most of them focus on bromide‐involved perovskite NCs, which may undergo dissolution and ion exchange within the FAPbI3 host, potentially resulting in an enlarged band gap. In this work, we employ butylamine‐capped CsPbI3 NCs (BPNCs) as additives in PSCs, which can be well maintained and serve as seeds for regulating the crystallization and growth of perovskite films. The resultant perovskite film exhibits larger domain sizes and fewer grain boundaries without compromising the band gap. Moreover, BPNCs can alleviate lattice strain and reduce defect densities within the active layer. The PSCs incorporating BPNCs show a champion power conversion efficiency (PCE) of up to 25.41 %, well over both Control of 22.09 % and oleic acid/oleylamine capped CsPbI3 NC (PNC)‐based devices of 23.11 %. This work illustrates the key role of nanosized seed surfaces in achieving high‐performance photovoltaic devices.
Mechanochemical Iron‐Catalyzed Nitrene Transfer Reactions: Direct Synthesis of N‐Acyl Sulfonimidamides from Sulfinamides and Dioxazolones
Authors: Pan Shulei , Mulks Florian F. , Wu Peng , Rissanen Kari , Bolm Carsten
Published: December 2023

A mechanochemical synthesis of sulfonimidamides by iron(II)‐catalyzed exogenous ligand‐free N‐acyl nitrene transfer to sulfinamides is reported. The one‐step method tolerates a wide range of sulfinamides with various substituents under solvent‐free ambient conditions. Compared to its solution‐phase counterpart, this mechanochemical approach shows better conversion and chemoselectivity. Mechanistic investigations by ESI‐MS revealed the generation of crucial nitrene iron intermediates.
Strain‐Induced Heteromorphosis Multi‐Cavity Cages: Tension‐Driven Self‐Expansion Strategy for Controllable Enhancement of Complexity in Supramolecular Assembly
Authors: Wang Jun , Jiang Zhilong , Yin Jia‐Fu , Zhao He , Dong Qiangqiang , Li Kaixiu , Zhong Wanying , Liu Die , Yuan Jie , Yin Panchao , Li Yiming , Lin Yifan , Chen Mingzhao , Wang Pingshan
Published: December 2023

Coordinative supramolecular cages with adjustable cavities have found extensive applications in various fields, but the cavity modification strategies for multi‐functional structures are still challenging. Here, we present a tension‐driven self‐expansion strategy for construction of multi‐cavity cages with high structural complexity. Under the regulation of strain‐induced capping ligands, unprecedented heteromorphosis triple‐cavity cages S2/S4 were obtained based on a metallo‐organic ligand (MOL) scaffold. The heteromorphosis cages exhibited significant higher cavity diversity than the homomorphous double‐cavity cages S1/S3; all of the cages were thoroughly characterized through various analytical techniques including (1D and 2D) NMR, ESI‐MS, TWIM‐MS, AFM, and SAXS analyses. Furthermore, the encapsulation of porphyrin in the cavities of these multi‐cavity cages were investigated. This research opens up new possibilities for the architecture of heteromorphosis supramolecular cages via precisely controlled “scaffold‐capping” assembly with preorganized ligands, which could have potential applications in the development of multifunctional structures with higher complexity.
D‐galactose might mediate some of the skeletal muscle hypertrophy‐promoting effects of milk—A nutrient to consider for sarcopenia?
Authors: Homolak Jan , Babic Perhoc Ana , Virag Davor , Knezovic Ana , Osmanovic Barilar Jelena , Salkovic‐Petrisic Melita
Published: December 2023

Sarcopenia is a process of progressive aging‐associated loss of skeletal muscle mass (SMM) recognized as a serious global health issue contributing to frailty and increased all‐cause mortality. Exercise and nutritional interventions (particularly intake of dairy products and milk) demonstrate good efficacy, safety, and broad applicability. Here, we propose that at least some of the well‐documented favorable effects of milk and milk‐derived protein supplements on SMM might be mediated by D‐galactose, a monosaccharide present in large quantities in milk in the form of disaccharide lactose (milk sugar). We suggest that ingestion of dairy products results in exposure to D‐galactose in concentrations metabolized primarily via the Leloir pathway with the potential to (i) promote anabolic signaling via maintenance of growth factor (e.g., insulin‐like growth factor 1 [IGF‐1]) receptor mature glycosylation patterns; and (ii) provide extracellular (liver glycogen) and intracellular substrates for short (muscle glycolysis) and long‐term (muscle glycogen, intramyocellular lipids) energy availability. Additionally, D‐galactose might optimize the metabolic function of skeletal muscles by increasing mitochondrial content and stimulating glucose and fatty acid utilization. The proposed potential of D‐galactose to promote the accretion of SMM is discussed in the context of its therapeutic potential in sarcopenia.
Dynamic capabilities for sustainability: Toward a typology based on dimensions of sustainability‐oriented innovation and stakeholder integration
Authors: Ortiz‐Avram Daniela , Ovcharova Nelly , Engelmann Alexander
Published: December 2023

This study aims to synthesize the current state of knowledge on conceptualizations of dynamic capabilities for sustainability (DCsS)—patterns of behavior in organizations specialized in adapting to sustainability demands. Our main goal is to elucidate the theoretical nature of the DCsS construct and provide a theoretical foundation for future empirical works. We perform a systematic literature review focused on existing conceptualizations of DCsS. Our content analysis of 86 articles reveals two emerging dimensions that account for variation in DCsS definitions: (i) the novelty degree of pursued sustainability‐oriented innovations and (ii) the level of stakeholder integration. Based on these dimensions, we identify four distinct types of DCsS: (1) firm‐level eco‐efficiency; (2) Firm‐level transformation; (3) supply chain or network level eco‐efficiency; and (4) systemic transformation. We illustrate the predominant underlying practices and related outcomes of each type, as described in the literature. By developing a typology that integrates distinct conceptualizations, we substantiate and clarify the DCsS construct, thus providing a fruitful starting point for more distinct and focused operationalizations of DCsS. By conceptualizing sustainability‐oriented innovation and level of stakeholder integration as integral dimensions constituting DCsS, we offer a more nuanced theoretical understanding of the DCsS construct.
Low‐CO2 cements based on magnesium oxide / hydromagnesite blends – hydration mechanism and mechanical properties
Authors: Winnefeld Frank , German Alexander , Lura Pietro , Rentsch Daniel , Lothenbach Barbara
Published: December 2023

Binders based on blends of reactive magnesia and hydromagnesite are low‐CO2 or even carbon‐negative cements in case the MgO is generated from magnesium silicates or Mg‐containing brines. When MgO is hydrated with water alone, a well crystalline brucite forms, but no measurable strength is developing. In the presence of hydromagnesite, the hydration of MgO is accelerated and the hydrate assemblage is changed. A poorly‐crystalline brucite containing some carbonate is the main hydration product. Furthermore, a kind of “gel‐water” is observed, which is lost at temperatures above 40‐60°C. This brucite‐like phase is responsible for strength formation in MgO‐hydromagnesite blends. After 28 days, a mortar compressive strength is reached similar to the one of a Portland cement of strength class 32.5.
The early bonding performance of geopolymer for repair: Effect of mix proportion of cement substrate
Authors: Xiong Guiyan , Guo Xiaolu , Cundy Andrew
Published: December 2023

Geopolymer can be potential Portland cement alternatives or supplement for concrete repair. In order to understand the bonding mechanism of geopolymer repairing materials, the effect of the mix proportion of cement mortar substrate on the early bonding performance was studied. For repaired composites by geopolymer, with the increase of sand‐to‐cement ratio of cement substrate from 1.5 to 2.5, the trends in the interfacial flexural‐tensile strength and slant shear strength were the same, both decreasing, which may be explained by the combined effect of surface porosity and the amount of surface cement pastes. And with the rise of the water‐to‐cement ratio of cement substrate from 0.4 to 0.5, the interfacial flexural‐tensile strength also increased mainly because of the increase in the surface porosity of the substrate, while the slant shear strength decreased resulting from the impact of compressive strength of the substrate. This indicates that the interfacial flexural‐tensile test is more suitable for the evaluation of the bonding performance than the slant shear test when the mix proportions of substrate vary.
Nottenkämperton – Der Weg zum puzzolanischen Zusatzstoff
Authors: Ludwig Horst‐Michael , Müller Matthias , Morgenthal Guido , Eckert Thomas , Wellmann Justin
Published: December 2023

Die Anwendung calcinierter Tone als Zementsubstitut ist seit einigen Jahren Gegenstand intensiver Forschung. Dennoch steht, insbesondere in Deutschland, die Anwendung dieser Materialien erst am Anfang. Mit dem prognostizierten Einbruch der Hüttensand‐ und Flugascheproduktion werden calcinierte Tone auch in Deutschland mittelfristig einen wichtigen Stellenwert einnehmen. Aus Gründen der Wirtschaftlichkeit und Verfügbarkeit kommt insbesondere den „unreinen” Tonen mit geringen Kaolingehalten eine besondere Bedeutung zu. Im Rahmen dieser Studie wurde die Eignung eines vorwiegend illitischen Tones mit vielen Nebenbestandteilen für die Anwendung im Zement untersucht. Trotz des geringen Tonmineralgehaltes wurde nach der Calcination ein guter Festigkeitsbeitrag erreicht, bei gleichzeig nur geringfügig verringerter Verarbeitbarkeit. „Unreine” kaolinarme lokale Tone können demnach das Potential dafür bieten, Hüttensand und Flugasche in der Zementproduktion in Deutschland adäquat zu ersetzen. In einem weiterführenden Forschungsprojekt soll die Voraussetzung dafür geschaffen werden, eine industrielle Nutzung des untersuchten Tonvorkommens durch die Herstellung calcinierter Tone zu ermöglichen.
Compressive and tensile behaviour of alkali‐activated slag‐based concrete incorporating single hooked‐end steel fibres
Authors: Rossi Laura , Patel Ravi A. , Dehn Frank
Published: December 2023

The effect of single hooked‐end steel fibres, namely Dramix® 3D, on the mechanical performance of alkali‐activated slag‐based concrete (AASC) and Portland cement concrete (PCC) has been investigated. Compressive strength, modulus of elasticity, stress‐strain response under uniaxial compression and tension, splitting tensile strength and flexural strength have been evaluated. The experimental results show that AASC incorporating 3D fibres in a volume fraction of 0.75% exhibits an enhanced behaviour, under both compression and tension, in comparison to PCC incorporating the same fibre type and dosage. Although the reference mixes show similar compressive strength, 3D fibres enhance the modulus of elasticity, splitting tensile strength and flexural strength of AASC of 8.6%, 61.7% and 12.8%, respectively, while for PCC 1.1%, 42.2% and 16.1%, respectively. Three‐point bending tests show the effect of 3D fibres on the response of AASC and PCC under flexural loading. Although fibres have a limited effect on the strength corresponding to the limit of proportionality (LOP), they enhance the post‐peak behaviour, increasing the residual flexural strength and the material ductility. Finite element analysis has been performed to predict the flexural behaviour of steel fibre‐reinforced AASC (FRAASC) under flexural loading. The Concrete Damage Plasticity (CDP) model implemented in ABAQUS software can predict the flexural response of FRAASC quite accurately, although additional experimental data are needed to calibrate the model for different alkali‐activated matrix types.
MgO‐based binders
Authors: Lothenbach Barbara , Bernard Ellina , German Alexander , Winnefeld Frank
Published: December 2023

To limit global temperature rise to below 2°C, we need to radically and rapidly change the way we build and use materials, since construction is responsible for 20‐40% of industrial CO2 emissions. Magnesium carbonate‐based cements have the potential to become a major carbon sink in construction industry, as CO2 will not be emitted during their production, but CO2 will rather be bound during hardening. Two different reaction mechanisms lead to setting and hardening of such HMC cements: i) hydration of MgO‐Mg‐carbonate, also in blends with silica and other mineral additions, in the presence of water or salt solutions (such as sodium bicarbonate solution) at ambient conditions or ii) carbonation hardening of MgO‐based systems at increased CO2 partial pressure and/or at increased temperatures.

However, the utilization of hydrated magnesium carbonate and magnesium silicate cements is currently hampered by the lack of systematic experiments and of fundamental understanding of the factors affecting the hardening process, mechanical properties, long‐term behavior and durability. In particular, the role of temperature, relative humidity and addition of supplementary cementitious materials and/or industrial by‐products has not been systematically investigated. We need knowledge both on the practical side through systematic experiments with pastes, mortars and concretes as well as on a fundamental level through solubility and sorption experiments and thermodynamic modelling. In addition, reaction kinetics need to be optimized as well as the early formation of the preferred phases (stability enhancement) to develop efficient HMC cements for construction. Due to the socio‐economic relevance of cement and concrete, the impact of such “carbon”‐negative cements may go beyond a purely scientific one and lead to technological breakthroughs to the benefit of environment and society.
1:1 or 2:1 ‐ Does it matter for calcined clay as supplementary cementitious material?
Authors: Thienel Karl‐Christian , Scherb Sebastian , Beuntner Nancy , Maier Matthias , Sposito Ricarda
Published: December 2023

Calcined clays are the most promising future supplementary cementitious material which are capable of replacing fly ashes and blast furnace slag on the long run due to their potential to achieve high cement replacement levels and their global availability. In the last decade most research has focused on calcined clays rich in the 1:1 kaolinite. Clay with less than 20 to 25 % kaolinite were seen as worthless. Even the content of 2:1 phyllosilicates in the kaolinitic clays was neglected and not even mentioned although especially these clays are dominant in areas like central and northern Europe. Here, highly kaolinitic clays are rare or used by other industries leading to high prices. This paper is based on published works and highlights whether information obtained for calcined 1:1 dominated clays can be applied for calcined 2:1 dominated clays or not and where further research is needed.
Frühe Hydratation von C3S in Gegenwart von Metakaolin
Authors: Sowoidnich Thomas , Damidot Denis , Cölfen Helmut , Rößler Christiane , Ludwig Horst‐Michael
Published: December 2023

Die Verwendung von kalziniertem Ton als Zementersatzstoff ist ein vielversprechender Weg, um die künftige Zementproduktion umweltfreundlicher zu gestalten und den CO2‐Fußabdruck von Beton zu verringern. Jedoch wird durch den Ersatz von kalziniertem Ton wird die Zementhydratation häufig verzögert. Obwohl die kombinierte Verwendung von Kalkstein und kalziniertem Ton mit Portlandzement die Verzögerung kompensieren kann, werden die Ursachen für diesen Effekt noch immer diskutiert. Insbesondere die Rolle der gebildeten C‐A‐S‐H‐Phasen in Kombination mit C‐S‐H‐Phasen ist umstritten. Die vorliegende Studie untersucht die geschilderte Verzögerung in Modellsystem C3S und Metakaolin.

Die Hydratationsreaktionen von Metakaolin und C3S wurden mittels optischer Emissionsspektroskopie, Rasterelektronenmikroskopie, Röntgenbeugung und Reaktionskalorimetrie analysiert. Die Ergebnisse zeigen, dass Calcium‐ und Sulfationen eine dominierende Rolle für die Reaktionsgeschwindigkeit von Metakaolin spielen, was sich wiederum auf die Hydratationsgeschwindigkeit von C3S auswirkt. Die Rolle der C‐A‐S‐H‐ gegenüber der C‐S‐H‐Bildung wird in diesem Zusammenhang hervorgehoben.
Reaktivitätsuntersuchungen von calcinierten Tonen mit geringem Metakaolingehalt
Authors: Sowoidnich Thomas , Hoffmann Christopher , Rößler Christiane , Ludwig Horst‐Michael
Published: December 2023

Die Verwendung von kalziniertem Ton als Ersatzstoff für Zement bietet vielversprechende Möglichkeiten, um die zukünftige Zementproduktion umweltfreundlicher zu gestalten und den CO2‐Fußabdruck von Beton zu reduzieren. Die Eignung für einen Einsatz als Kompositmaterial hängt wesentlich von der Reaktivität der calcinierten Tone ab und ist von verschiedenen Parametern abhängig. Die vorliegenden Untersuchungen wurden an 4 verschiedenen Tongemengen mit unterschiedlichen Brenntemperaturen durchgeführt. Es wurde die puzzolanische Reaktivität nach modifiziertem Chapelle Test sowie nach dem R3‐Test (engl.: „Rapid, Relevant and Reliable”) beurteilt.

Die Ergebnisse zeigen, dass auch bei einem Metakaolingehalt von unter 15% der R3‐Test hinreichende Aussagen zur Reaktivität der calcinierten Tone ermöglicht. Im Gegensatz dazu ist der Chapelle Test weniger gut geeignet.
Stability of calcined clays during storage
Authors: Pesch Katja , Schulze Simone E. , Rickert Jörg
Published: December 2023

Usage of calcined clay as a cement main constituent is spotlighted as an important part of the decarbonisation of the cement industry. In particular, little knowledge is available on the storage stability of calcined clays. Therefore, the influences of fineness, temperature and humidity for different timescales of storing were determined. Two samples of a calcined kaolinitic‐illitic clay of different fineness (crushed and ground) were stored sealed in a desiccator, as well as at 20 °C and 60 % rel. humidity, and at 40 °C and 100 % rel. humidity. The clay's mineralogical composition, moisture and chemically bound water content were analysed at 7, 28, and 91 days of storage respectively. Additionally, their reactivity was determined acc. ASTM C 1897‐20 and acc. EN197‐1.

The calcined clays which were stored in a desiccator showed only slight alteration over the period of 91 days. Samples stored at 20 °C and 60 % rel. humidity, contained small amounts of moisture and chemically bound water, regardless of their fineness. Storage at 40 °C and 100 % rel. humidity led to a huge increase in moisture and chemically bound water, especially at high fineness. The reactive silicon of the fine samples was diminished independent of storage conditions over time, whereas the coarse samples showed no changes. Samples stored at 40/100 showed a strong decrease in their heat of hydration over 91 days.

This study implicates, that the analysed calcined clay could be stored as coarsegrained fraction at normal conditions.
Synergistic effect of aluminum sulfate and triethanolamine on the hydration of metakaolin blended cement
Authors: Zhang Liheng , Lu Zichen , Liu Zhiwei , Sun Zhenping
Published: December 2023

Shotcrete is regarded as an indispensable component in the construction of tunnels and mines, which can stabilize the tunnel wall and prevent groundwater infiltration. Along with the massive railway construction in China's mountainous region, it is unavoidable to build more tunnels, and then the used amount of shotcrete increases dramatically. Calcined clay blended cement is one promising low‐carbon cementitious material and metakaolin (MK) is the main reactive component in calcined clay. Considering the high demand for shotcrete and the urgently needed carbon neutrality in China, it is necessary to contain more MK in the cement of shotcrete.

Beside the cement, accelerator is also necessary for the production of shotcrete. Aluminum sulfate (AS) and triethanolamine (TEA) are two representative components in the alkali‐free liquid accelerator. However, limited researches were conducted regarding the synergistic effect of AS and TEA on the setting and hardening performance of the metakaolin blended cement (OPC‐MK).

Hence, in order to clarify the effect of TEA and AS on the hydration of OPC‐MK, different dosages of TEA were added to AS solution and their effects on setting performance, compressive strength and hydration kinetics of OPC‐MK were investigated. It is found that, with the presence of both AS and TEA, a high dosage of TEA facilitates the reaction of the aluminate phase while greatly retards the silicate reaction. More importantly, TEA can promote the dissolution and pozzolanic reaction of MK. Thereby a dense structure can be formed and the compressive strength of pastes at 28 d is enhanced. At last, the interactions between TEA, AS and OPC‐MK is thoroughly analyzed, which could provide a theoretical basis for the wide application of low‐carbon cement in shotcrete.
Reliability and cost analysis of selected repair methods of the new TR Instandhaltung
Authors: Lozano‐Valcarcel Juan Mauricio , Cassiani Juan Daniel , Kraenkel Thomas , Gehlen Christoph , Kessler Sylvia
Published: December 2023

In Germany, the new Technical Specification for Maintenance (TR Instandhaltung) forms the basis for planning, management, and implementation of maintenance measures on reinforced concrete structures. In the case of chloride‐induced corrosion, different concrete repair methods are specified therein for defined depth‐dependent chloride concentrations in relation to the concrete cover, following thus a prescriptive approach. In contrast, a full‐probabilistic, performance‐based approach sets limits to the so‐called “reliability index” (β). These limits are related to a maximum accepted probability of occurrence of an unwanted event, which in the case of chloride exposure, is the corrosion of the reinforcement. Since the value of β depends inherently on the depth‐dependent chloride concentration and the concrete cover, the limits set on them by the TR must be related to an implicit value of β. Therefore, in this contribution, these limits were analysed and evaluated. Additionally, the resulting costs of each method were estimated and analysed in terms of β at the time of the repair. Both the limits and the resulting costs provide helpful information in the context of a performance‐based approach for the through‐life management of reinforced concrete structures.
Concrete for Reconstruction of Structures
Authors: Abramowicz Małgorzata , Plugin Andrii , Borziak Olga , Zhuravel Vitalii
Published: December 2023

To eliminate significant wear of building structures, increase the bearing capacity when operating conditions change, it may be necessary to restore / increase the bearing capacity of structures. One of the most common methods of strengthening is to increase the section of the structure by installing duplicate elements. For reinforced concrete structures, reinforcement should include the restoration of the surface layer of concrete, the filling of cracks and chips. The paper considers a method for increasing the adhesion of new concrete to the old one. Concrete formulations are proposed for strengthening structures whose concrete has already been damaged due to exposure to aggressive media. The formation of the physical and mechanical parameters of new concretes, their adhesion to old concretes was carried out due to the directed formation of their structure. The formation of the structure at the mesolevel is affected by the introduction of the optimal amount of microfillers and reinforcing fibers. At the micro‐ and submicrolevel, due to the introduction of a complex chemical additive, additional crystalline hydrates are synthesized, strengthening the contact zone between the old concrete and the new one.
Increase in physical and mechanical properties of decorative concretes for the post‐war restoration of residential and public buildings in the Kharkiv region with the addition of highly dispersed calcite (chalk)
Authors: Chepurna Svitlana , Dudka Olena , Chepurnyi Yevhenii
Published: December 2023

During the war active, a huge number of residential and public buildings were destroyed not only in Kharkiv and the region, but throughout Ukraine. For the restoration of destroyed buildings, new types of cement will be needed to look for and will be created decorated concretes based on them that would provide high operational and technological properties of constrictions and will be focused on local materials. Carbonate additive such as highly dispersed calcite (chalk) can be used for as local additive for concrete due to significant reserves are located in Kharkiv region. In the article research on the impact of joint action additive of highly dispersed calcite (chalk) and natural pigment (ocher) is presented by physical and mechanical properties such as density, strength, water resistance, and frost resistance. It has been established that, depending on the percentage of highly dispersed calcite (chalk), the physical and mechanical properties are changed irregularly. On the basis of the conducted researches it was established that the optimal amount of the addition of high‐fossil chalk, which provides increased frost resistance and corrosion resistance of concrete in an aggressive environment, containing chlorides, sulfates and magnesium ions, is from 10 % to 30 %. In addition, it increases density, compressive strength, stretching strength at bending. At the same time, it should be noted at an increased amount of fine chalk to 40% leads to a decrease in physical and mechanical characteristics. But the introduction of plasticizer in the amount of 0.5% leads to increased compressive strength and, accordingly, increases the positive qualities of chalk. The concrete compositions that getting with high decorative and operational properties are allowed to use them for the restoration of the city and increase in urban space.
Forschungsansätze für Recycling von Calciumsulfat‐Fließestrichen
Authors: Hecker Andreas , Schnell Alexander , Ludwig Horst‐Michael
Published: December 2023

Kurzfassung

Gips ist ein wichtiger Baustoff und wird vor allem im Hochbau im Innenbereich eingesetzt. Neben Gipskarton‐ und Gipswandbauplatten werden calciumsulfathaltige Baustoffe in Form von Estrichen für Fußböden und auf Wand‐ und Deckenoberflächen als Putz verwendet. Die Nachfrage an Rohgips wird momentan noch zu ca. 60 % mit Rauchgasentschwefelungsgips (REA‐Gips, Nebenprodukt aus der Kohleverstromung) gedeckt. Etwa 40 % werden durch den Abbau von Naturgips zugeführt [1]. Entsprechend den nationalen und internationalen Klimaschutzzielen und der damit verbundenen Energiewende wird die Versorgung der Gipsindustrie mit REA‐Gips sehr stark zurückgehen. Das Recycling von Gipsbaustoffen wird ein eher kleiner aber wichtiger Beitrag zur effektiven Ressourcennutzung und ‐ schonung werden. Momentan sind Gipskartonplatten die wichtigste Versorgungsquelle für das Gipsrecycling [1]. Eine zweite, massenmäßig interessante Quelle könnten ausgebaute Calciumsulfatestriche sein. Diese Ressource wurde bis jetzt weder bilanziert noch verwertet. In einem Verbundforschungsprojekt (Wandel durch Innovation in der Region) beschäftigen sich Unternehmen und Hochschulen damit, verschiedene Calciumsulfatressourcen zu bewerten und anwendungstechnisch zu untersuchen. Erste Ergebnisse zur Wiedernutzung von Calciumsulfatestrichen liegen jetzt vor.
Rheology of low‐clinker suspensions: Multiscale comparison of the effect of PCE on thixotropy
Authors: Nicia David , Fobbe Nicholas , Jansen Daniel , Lowke Dirk
Published: December 2023

Addressing climate change requires reducing the carbon footprint of cement‐based building materials on a global scale. One promosing approach involves decreasing the clinker content by incorporating fine supplementary cementitious materials (SCM), which, however, can increase the stickiness of fresh concrete. Along with viscosity, thixotropic structural build‐up is a critical rheological parameter that impacts the stickiness of the SCM‐rich suspensions. Thus, it is essential to gain a precise understanding of how the molecular structure and mode of addition of polycarboxylate ethers (PCE) affect the thixotropic structural build‐up in low‐clinker suspensions. To address this issue, we investigate key parameters affecting thixotropy, specifically PCE adsorption and early hydration kinetics at the cement paste and mortar level, using a multiscale approach. In an application‐oriented concept, we maintain a constant yield stress by varying the PCE dosage to achieve constant workability. Our results demonstrate that higher thixotropy correlates with increased PCE charge density and direct addition in cement pastes and mortars. Moreover, it is indicated that increasing specific surface area and ettringite contents promote additional thixotropy‐enhancing mechanisms.
Decarbonisation and preservation of natural resources along the cement and concrete value chain
Authors: Rickert Joerg
Published: December 2023

There are major challenges which the cement industry in Germany and the entire cement and concrete value chain are facing in their quest for climate neutrality and preservation of natural resources. The studies on decarbonisation and resource conservation recently published by VDZ underline the claim of German cement manufacturers to actively promote decarbonisation and to further significantly reduce the use of primary raw materials in the value chain of cement and concrete. Within the context of a 2050 scenario, various potentials for decarbonisation and resource conservation are being identified and quantified. In addition, the necessary prerequisites and action strategies for implementing the savings potential are explained.
Effect of Grain Size and Layer Thickness on Hardened State Properties in Selective Cement Activation
Authors: Mai Inka , Herding Friedrich , Lowke Dirk
Published: December 2023

This article demonstrates the effect of varying the maximum grain size and the layer thickness of the particle bed on hardened state properties in Selective Cement Activation (SCA). The compressive strength and geometry (deviation from nominal geometry, surface roughness) are analyzed. Supplementary investigations (μCT, μRFA) are performed to explain the causes of the observed effects. It is found that the compressive strength of the manufactured specimens increases with decreasing layer thickness. This is attributed to reduced process‐induced segregation of the particle bed and fewer process‐induced voids. The geometric precision as well as the surface roughness of the printed test specimens do not differ significantly. As the grain size increases, the amount of compaction required to achieve the target packing density decreases. The compressive strength was found to increase when the grain size in the specimen is reduced. As the finer particle mixtures tend to have less void formation as a result of water application, an increased density of the specimen can be observed. The lower porosity as well as the smaller pores also have a favorable effect on geometric precision, which tends to increase with reduced grain size. At the same time, a lower surface roughness is also present.
Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance
Authors: Straßer Alexander , Kränkel Thomas , Gehlen Christoph
Published: December 2023

This research aims to integrate the Wire Arc Additive Manufacturing (WAAM) process into the Selective Paste Intrusion (SPI) process to enable the production of reinforced concrete elements with complex geometries. However, the high temperatures generated during the steel melting process in WAAM can locally lead to a full stop of hydration which consequently is linked to a decrease of the mechanical properties of the concrete in the bonding zone around the reinforcing bar. This study aims to determine the maximum allowable temperature at which concrete retains sufficient hardening conditions which allows strength development when combining SPI with WAAM. In practical application, this temperature limit can directly be affected by e.g. the protruding length of the WAAM‐reinforcing bar above the SPI particle bed or external cooling strategies. As continuation of previous research, this study establishes a link between actual and targeted temperatures in the steel bar to allow the combination of WAAM and SPI processes. Temperature limits without compromising mechanical performance are investigated, and the need for and extent of additional cooling measures are evaluated. The results show that temperatures of the concrete in the fresh state can reach up to 70°C without weakening its mechanical performance.
Rheologisches Verhalten von faserbewehrtem LC3‐Feinkornbeton im Kontext der additiven Fertigung
Authors: Reißig Silvia , Bedolla Carolin , Meyer Tamara , Mechtcherine Viktor
Published: December 2023

Kurzfassung

In den letzten Jahren wurde die Entwicklung digitaler Bauverfahren, wie der 3D‐Druck mit Beton, mit zunehmendem Interesse von der Bauindustrie verfolgt und erprobt, da er einen vielversprechenden Ansatz für viele aktuell in dieser Branche bestehende Probleme darstellt. Gleichzeitig wird der Ruf nach nachhaltigen Bindemitteln immer lauter. Es erscheint logisch, beide Herangehensweisen zusammenzuführen, um eine zukunftsfähige Baumethode zu etablieren. Darüber hinaus soll die Integration einer Bewehrung im Kontext der additiven Fertigung weitere Vorteile bringen. Der praktischste Ansatz ist die Einbringung von kurzen, im Beton dispergierten Fasern, als Teil des Extrusionsprozesses. Aus technischer Sicht kann die Umsetzung dieses ökologisch und ökonomisch vorteilhaften Konzepts aber nur gelingen, wenn die 3D‐druckbaren Materialien im Frischzustand rheologische Eigenschaften aufweisen, die den hohen Anforderungen der komplexen Prozesskette des 3D‐Drucks entsprechen. Aus diesen Gründen wird in diesem Beitrag ein erster Einblick in das rheologische Verhalten von PE‐faserbewehrten 3D‐druckbaren Feinkornbetonen (printFRC) auf Basis eines nachhaltigen Bindemittels vorgestellt.
Additive manufacturing technology for the continuous production of precision concrete elements
Authors: Funke Henrik , Lindner Marco , Rudolph Enrico , Gelbrich Sandra
Published: December 2023

This work reports about a combined additive manufacturing technology – concrete spraying and extrusion – for a continues production of precision concrete elements for modular civil construction. In order to achieve the goal, a fine‐grained concrete mix was developed that covers the technical production properties for both spraying and extrusion. In a next first step, a spray‐extrusion multi‐tool nozzle was developed and tested for spraying and extrusion of the fine‐grained concrete mixture. In addition to complete the robot‐assisted flow production process, force transmission elements were developed, which can be automatically integrated into the extruded concrete matrix in the non‐cured green state in accordance with the load. This holistic automated production technology opens new fields of application in the construction industry that were previously not possible with classic methods.
Opportunities and barriers of pozzolanic cements
Authors: Canonico Fulvio , Mutke Sabine , Martín Araceli Pablos , Pellegrino Alberta
Published: December 2023

Natural pozzolans have been used as building materials since ancient times. They are used as a supplementary cementitious material in combination with portland clinker to produce cements, characterized by high mechanical strengths and good durability performance. In the past the production of pozzolanic cement was mostly restricted to countries with natural pozzolan availability (Italy, Turkey, Greece, Philippine for example) and considered or even rejected in other countries that had the possibility of using other types of SCMs such as slag or fly‐ash. The market acceptance of natural pozzolanic cement also shows regional dependency. Colour and water demand strongly affect the perception and rheological properties of concrete containing natural pozzolan resulting in poor acceptancy in regions not used to working with this type of cement. Although, this SCM has been studied for very long time, today it makes sense to look closely at new pozzolanic binders. Innovative types of pozzolanic cement with very low clinker content are approaching the traditional cement market, due to the need for clinker factor reduction, and to the availability of separate grinding technology. New applications are being investigated with the aim of exploiting the behaviour of certain pozzolanic material to act as CO2 adsorbers for the removal of the exhaust gas during the production process. This paper will provide an overview of the most recent research work dealing with natural pozzolanic cement and the possible future opportunities and barriers offered by this very traditional and long‐used building material.
Near‐Nozzle Mixing for Additive Manufacturing of Cementitious Mortar: A Homogeneity Study
Authors: Hechtl C. Maximilian , Kränkel Thomas , Gehlen Christoph
Published: December 2023

This paper investigates the Near‐nozzle Mixing (NNM) technique for 3D printing cementitious mortar, focusing on achieving continuous and homogeneous material properties. The NNM's ability to print Natural Sand Mortar (NSM), Recycled Aggregate Mortar (RAM), and Lightweight Mortar (LWM) was assessed. Fresh and hardened properties of each mortar were examined, emphasizing standard deviation (STD) and coefficient of variation (CV) to measure material homogeneity. Fresh properties included slump flow, yield stress, air void volume, density, and water‐to‐cement ratio, while hardened properties covered compressive strength, flexural strength, hardened density, and thermal conductivity. Results showed low CV values for all mortar types, indicating high consistency and homogeneity. NNM showed is capability to print of various materials with customized properties. NSM showed the highest compressive strength, RAM balanced strength and sustainability, and LWM provided the best thermal insulation. The study highlights NNM's versatility and potential for construction applications requiring tailored properties, proving it a promising additive manufacturing solution. The research serves as a foundation for future studies on graded multi‐material printing.
Influence of the load frequency and moisture content on fatigue deterioration of high‐strength concrete
Authors: Ali Mohamed Abubakar , Oneschkow Nadja , Lohaus Ludger , Haist Michael
Published: December 2023

With the expansion of offshore wind energy systems, the number of fatigue‐loaded concrete structures exposed to high moisture contents has significantly increased in the last decades. Investigations in the literature show a strong reduction of fatigue resistance with increasing moisture content of the concrete. However, a detailed quantified understanding of the influence of the moisture content and the underlying damage mechanisms is still lacking. In a conjoint project as part of the priority program SPP 2020 funded by the German Research Foundation (DFG), the water‐induced fatigue damage are investigated. In this paper, the results of compressive fatigue testes on high‐strength specimens with different moisture contents are presented. The cyclical loading was carried out at three different load frequencies and maximum stress levels, respectively. The results show that the damaging effect due to fatigue loading at high moisture content is more pronounced with decreasing stress levels and decreasing frequencies. Considering the strain development and acoustic emissions the results indicate that different damage mechanisms are acting with increasing moisture content of concrete. These mechanisms are elaborated in this paper.
Leichte Gesteinskörnungen hergestellt aus Bau‐ und Abbruchabfällen – Applikation in der Denkmalpflege
Authors: Seher Julia , Rübner Katrin , Müller Constanze , Pniok Nicole , Dreisow Bianca
Published: December 2023

Kurzfassung

Im Rahmen des BMBF‐geförderten Forschungsprojekts ReMin – REALight werden in einem Projektteam aus Industriepartnern und Forschungseinrichtungen unter Koordination der Bauhaus‐Universität Weimar leichte Gesteinskörnungen aus Bau‐ und Abbruchabfällen und industriellen Nebenprodukten auf thermischem Weg hergestellt. Die Aufgabe der Bundesanstalt für Materialforschung und ‐prüfung (BAM) ist es, diese im Drehrohrofen erzeugten Blähgranulate für gebundene Anwendungen in Beton und Mörtel umfassend zu charakterisieren. Gemeinsam mit der Opus Denkmalpflege GmbH wird die Applikation feiner, gebrochener Blähgranulate in leichten Steinergänzungsmörteln für die Restaurierung von Sandsteinobjekten untersucht. Hierzu wird ein zweischichtiges Mörtelsystem bestehend aus einem Füll‐ und einem Deckmörtel entwickelt. Erste Ergebnisse der Rezepturentwicklung verschiedener kalkhaltiger Leichtmörtel mit gebrochenen Blähgranulaten werden vorgestellt. Die neuen Leichtmörtel sind hinsichtlich der entwickelten Druckfestigkeit gleichwertig gegenüber herkömmlichen Restauriermörteln.
REALight ‐ Leichtgranulate und REA‐Gips aus feinkörnigen sulfatbelasteten Bau‐ und Abbruchabfällen
Authors: Schnell Alexander , Rübner Katrin , Seher Julia , Müller Anette , Liebezeit Steffen , Fenner Jacob , Martin Falk , Pniok Nicole
Published: December 2023

Kurzfassung

Ziel des Projekts REALight ist die Entwicklung einer Referenzanlage zur Herstellung von Leichtgranulaten (leichte Gesteinskörnungen) aus Bau‐ und Abbruchabfällen und zur Gipsrückgewinnung. Als Rohstoffe werden bisher ungenutzte oder auf niedrigem Niveau eingesetzte Bau‐ und Abbruchabfälle und industrielle Nebenprodukte verwendet. Als Produkte werden leichte Gesteinskörnungen hergestellt. Die Sulfatabtrennung durch eine thermische Zersetzung bildet die Grundlage für die zusätzliche Gewinnung von Rauchgasentschwefelungs‐Gips (REA‐Gips). Das Projekt wird im Rahmen der Fördermaßnahme „Ressourceneffiziente Kreislaufwirtschaft – Bauen und Mineralische Stoffkreisläufe (ReMin)” gefördert. ReMin ist eine Maßnahme zur Umsetzung des BMBF‐Forschungskonzepts „Ressourceneffiziente Kreislaufwirtschaft” als Teil der BMBF Strategie „Forschung für nachhaltige Entwicklung – FONA”. Ziel der Förderung ist es, den Ausbau der Kreislaufwirtschaft voranzutreiben. Im Mittelpunkt steht dabei die Bauwirtschaft mit ihrer hohen Nachfrage nach Rohstoffen und gleichzeitig großen Mengen an anfallenden mineralischen Abfällen. Am Projekt REALight sind 12 Partner aus verschiedenen Bereichen der Baustoffherstellung und ‐anwendung, Abfallaufbereitung, Verfahrenstechnik sowie Forschung und Entwicklung beteiligt.
Der Einfluss der Morphologie der Impfkristalle auf die Hydratation von Halbhydrat
Authors: Sakalli Yilmaz , Pritzel Christian , Trettin Reinhard , Killian Manuela S.
Published: December 2023

Kurzfassung

Der am häufigsten eingesetzte Beschleuniger für Halbhydrat sind Gipsimpfkristalle. In wieweit die Art dieser Kristalle (Morphologie und Größe) einen Einfluss auf die technischen Eigenschaften des entstehenden Gipssteins hat ist bislang nicht ausreichend geklärt. Daher wurde in der vorliegenden Arbeit der Einfluss verschiedener Impfkristalle, deren Morphologie durch Zusatzmittel beeinflusst wurde, untersucht. Impfkristalle auch in kleinen Mengen wirken beschleunigend, Neben den Impfkristallen kommt es während der Halbhydrat‐Hydratation zur Neubildung von Dihydratkristallen. Es konnte gezeigt werden, dass Impfkristalle in der vorgegebenen Morphologie weiterwachsen. Neu gebildete Kristalle sind nicht davon betroffen. Damit lassen sich ggf. Gefüge aus verschiedenen Kristallmorphologien einstellen.
A Bogue approach applied to BOF slag
Authors: Zepper Jonathan , Schollbach Katrin , van der Laan Sieger , Brouwers H.J.H
Published: December 2023

An industrial by‐product of the steel industry called basic oxygen furnace (BOF) slag has recently undergone extensive research for high‐end applications outside of road load and landfill. In contrast to the Bogue methodology used with regular Portland cement, BOF slag lacks a quick and straightforward quantitative phase analysis procedure that would allow it to be employed as a high‐end raw material. The main phases of BOF slag (C2S, C2(A,F), Ff, RO‐Phase, and f‐C) can be calculated using the method presented in this paper based on chemical composition.