717 research outputs found
Healcon: self-healing concrete to create durable and sustainable concrete structures
No full textWithin the theme ‘Self-healing materials for prolonged lifetime’ (NMP.2012.2.1-3) of the Seventh Framework Programme, self-healing concrete is an important topic. The project HEALCON, which deals with self-healing concrete to create durable and sustainable concrete structures, is funded by EU-FP7 and started in January 2013. The coordinator of the project is Prof. Nele De Belie (UGent) and the consortium partners are UGent, Avecom, TU Delft, Acciona, TUM, TTI, VTT, COWI, DTI, CEINNMAT, Devan and Fescon.
Adequate perpetuation of the road, tunnel and bridge network, is crucial to preserving European cohesion and business operations; and around 70% of this infrastructure is made of concrete. In order to garantuee liquid tightness of concrete structures, and enhance durability of elements prone to bending cracks, smart concrete with selfhealing properties will be designed.
Thanks to the existing expertise of the consortium in the field of self-healing concrete at a lab-scale, a thoughtful selection of promising techniques is possible.
- For early age cracks, a non-elastic repair material can be proposed, such as calcium carbonate precipitated by bacteria, or new cement hydrates of which the formation is stimulated by the presence of hydrogels.
- For moving cracks under dynamic load, an elastic polymeric healing agent is suggested.
Different healing agents and encapsulation techniques are tested and scaled up. Self-healing efficiency is evaluated in lab-scale tests using purposefully adapted monitoring techniques, and optimized with the help of suitable computer models.
Finally the efficiency is validated in a large scale lab test and implemented in an actual concrete structure. Life-cycle cost analysis will show the impact of the selfhealing technologies on economy, society and environment compared to traditional construction methods
Een monument voor het land : overheidsstatistiek in België, 1795-1870
No full textIn A monument to the country. Official statistics in Belgium, 1795-1870, Nele Bracke unravels why and how the Belgian state and its predecessors organized and developed an official statistical apparatus in order to collect numerical information. The study captures the underlying objectives and structures, as well as the methods to compile statistics. Nele Bracke investigates the meaning and significance of government statistics in the 19th-century State and society. In Belgium, early social scientists established an internationally renowned ‘statistical system’ designed to collect information about the country, the people and the society. This ‘statistical system’ was built around the ‘Commission centrale de Statistique’ (statistical committee) and the production of demographic, economic and agricultural censuses. In the first part of the book, the author analyzes the institutional history of the ‘Commission centrale de Statistique’ and its predecessors. In the second part of the book, she studies the censuses
Een monument voor het land. Overheidsstatistiek in België, 1795-1870
No full textIn A monument to the country. Official statistics in Belgium, 1795-1870, Nele Bracke unravels why and how the Belgian state and its predecessors organized and developed an official statistical apparatus in order to collect numerical information. The study captures the underlying objectives and structures, as well as the methods to compile statistics. Nele Bracke investigates the meaning and significance of government statistics in the 19th-century State and society. In Belgium, early social scientists established an internationally renowned ‘statistical system’ designed to collect information about the country, the people and the society. This ‘statistical system’ was built around the ‘Commission centrale de Statistique’ (statistical committee) and the production of demographic, economic and agricultural censuses. In the first part of the book, the author analyzes the institutional history of the ‘Commission centrale de Statistique’ and its predecessors. In the second part of the book, she studies the censuses
Een monument voor het land. Overheidsstatistiek in België, 1795-1870
No full textIn A monument to the country. Official statistics in Belgium, 1795-1870, Nele Bracke unravels why and how the Belgian state and its predecessors organized and developed an official statistical apparatus in order to collect numerical information. The study captures the underlying objectives and structures, as well as the methods to compile statistics. Nele Bracke investigates the meaning and significance of government statistics in the 19th-century State and society. In Belgium, early social scientists established an internationally renowned ‘statistical system’ designed to collect information about the country, the people and the society. This ‘statistical system’ was built around the ‘Commission centrale de Statistique’ (statistical committee) and the production of demographic, economic and agricultural censuses. In the first part of the book, the author analyzes the institutional history of the ‘Commission centrale de Statistique’ and its predecessors. In the second part of the book, she studies the censuses
Evidence for a role of nitric oxide in iron homeostasis in plants
No full textNitric oxide (NO), once regarded as a poisonous air pollutant, is now understood as a regulatory molecule essential for several biological functions in plants. In this review, we summarize NO generation in different plant organs and cellular compartments, and also discuss the role of NO in iron (Fe) homeostasis, particularly in Fe-deficient plants. Fe is one of the most limiting essential nutrient elements for plants. Plants often exhibit Fe deficiency symptoms despite sufficient tissue Fe concentrations. NO appears to not only up-regulate Fe uptake mechanisms but also makes Fe more bioavailable for metabolic functions. NO forms complexes with Fe, which can then be delivered into target cells/tissues. NO generated in plants can alleviate oxidative stress by regulating antioxidant defense processes, probably by improving functional Fe status and by inducing post-translational modifications in the enzymes/proteins involved in antioxidant defense responses. It is hypothesized that NO acts in cooperation with transcription factors such as bHLHs, FIT, and IRO to regulate the expression of enzymes and proteins essential for Fe homeostasis. However, further investigations are needed to disentangle the interaction of NO with intracellular target molecules that leads to enhanced internal Fe availability in plants.RKT is grateful to Department of Science and Technology-Science and Engineering Research Board (DST-SERB) New Delhi, for a Teachers Associateship for Research Excellence (TAR/2019/000064).Tewari, RK (corresponding author), Univ Lucknow, Dept Bot, Lucknow 226007, Uttar Pradesh, India.
[email protected]
Expect the Unexpected: Organizational Purpose as Enabler of Serendipitous Impact
No full textChristian Busch, author of The Serendipity Mindset: The Art and Science of Creating Good Luck, and Nele Terveen explain how purpose helps leaders connect the dots between grand challenges and strategic responses. When leaders expect the unexpected, the authors explain, they incent their stakeholders to embrace uncertainty so they can better guide their organizations through adversity and disruption. By leveraging the five practices of Serendipitous Impact (impact mission, impact leadership, impact governance, impact networks, and impact measurement) unexpected events can help leaders come up with solutions that often cannot be seen, let alone fully defined, in advance.https://www.cutter.com/journal/scaffolding-purpose-times-polycrisi
Consequences of the change in Eurotransplant allocation system on kidney allocation in children
No full textNon-destructive testing techniques for the observation of healing effects in cementitious materials: an introduction
No full textTo develop an appropriate method of self-healing for cementitious materials including the right composition and amount of suitable healing agents it is required to investigate the healing efficiency for certain material mixtures. While some researchers evaluate the regain in compressive strength by means of destructive load tests, this method is obviously second best in particular for field applications. In a large EU project the best candidates among the non-destructive testing methods are investigated to be applied in small and large laboratory experiments as well as at real structures in-situ. The paper is giving an introduction to these techniques and addresses also issues of structural health monitoring used for example to monitor the healing effects on a long term basis and to assess the condition of the structure, where self-healing techniques are applied
Microfibres and hydrogels to promote autogenous healing in cementitious materials
No full textCementitious materials are sensitive to crack formation and it would be beneficial if the material could stop the crack propagation, repair the damage and reach again the original liquid-tightness and/or strength. Therefore, a cementitious material with synthetic microfibres and superabsorbent polymers (SAPs) is proposed. Upon crack formation, the microfibres will become active and due to the bridging action, they will stop the opening of a crack, forcing the cementitious material to crack somewhere else. There, other fibres will become active. In this way, not one large crack, but several small healable cracks are formed.
Further cement hydration and calcium carbonate precipitation will seal the crack if sufficient building blocks and water are present. The building blocks are available through the well-designed mixture with a low water-to-binder (W/B) ratio and water is available through the inclusion of SAPs. These polymers are able to extract moisture from the environment and to provide it to the cementitious matrix for autogenous healing. This healing will lead to the regain in mechanical properties.
In this paper, the formed products are studied by means of optical and scanning electron microscopy. The healing efficiency was evaluated by reloading cracked and healed specimens and by comparing the new mechanical properties with the original properties.
The crack width was limited to 50 μm at 1% strain. While specimens without SAPs showed a regain of mechanical properties of 40-55% in wet/dry cycles, specimens with SAPs showed a total regain of 80-95%. Even in humid air, those specimens show partial healing of 35-55%. SAP B, a cross-linked potassium salt polyacrylate, showed better healing properties compared to SAP A, a copolymer of acrylamide and sodium acrylate. The smart mate with SAP B thus is an excellent material to use in future building applications
Most recent advances in the field of self-healing cementitious materials
No full textWhile the Japanese researchers Ohama et al. [1] already mentioned in 1992 that a self-healing effect was noticed when polymer-modified concrete without hardener was made, the real pioneer in the research on self-healing concrete is Carolyn Dry from Illinois. The first time she proposed the use of encapsulated polymers to obtain self-healing concrete dates back to 1994 [2] and based on her publication output, she remained active within this field until 2003 [3, 4]. Within this timeframe, Victor Li started his research on fiber-reinforced self-healing concrete in Michigan [5]. From 2000 onwards other researchers in Japan (Mihashi, Nishiwaki et al.) [6-8], France (Granger et al.) [9], the United Kingdom (Joseph et al.) [10] and the Netherlands (ter Heide et al.) [11] started their research on self-healing cementitious materials. However, it was only in 2007, when the Dutch IOP program on self-healing was granted and the first international conference on self-healing materials was organized in the Netherlands, that self-healing concrete gained world-wide attention and all over the world research groups started working on this topic. One year later, in Belgium or more specifically at the Magnel Laboratory for Concrete Research of Ghent University, research on self-healing concrete started. In this keynote, an overview of the most recent developments within the Magnel Laboratory will be given
- …
