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NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material. Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure. Moreover it enables the determination of moisture transport properties and the (re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing. However, as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale (< 10 mL) samples. This paper describes the capabilities of an NMR tomograph, which has been specifically optimized for the investigation of larger, heterogeneous building material samples (diameters of up to 72 mm, length of up to 700 mm) with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times (50 - 80 m s).
SLAMD-FIB-Case-Study
(2022)
With 8% of man-made CO2 emissions, cement production is an important driver of the climate crisis. By using alkali-activated binders part of the energy-intensive clinker production process can be dispensed with. However, because numerous chemicals are involved in the manufacturing process here, the complexity of the materials increases by orders of magnitude. Finding a properly balanced cement formulation is like looking for a needle in a haystack. We have shown for the first time that artificial intelligence (AI)-based optimization of cement formulations can significantly accelerate research. The „Sequential Learning App for Materials Discovery“ (SLAMD) aims to accelerate practice transfer. With SLAMD, materials scientists have low-threshold access to AI through interactive and intuitive user interfaces. The value added by AI can be determined directly. For example, the CO2 emissions saved per ton of cement can be determined for each development cycle: the more efficient the AI optimization, the greater the savings. Our material database already includes more than 120,000 data points of alternative cements and is constantly being expanded with new parameters. We are currently driving the enrichment of the data with a life cycle analysis of the building materials. Based on a case study we show how intuitive access to AI can drive the adoption of techniques that make a real contribution to the development of resource-efficient and sustainable building materials of the future and make it easy to identify when classical experiments are more efficient.
In 2019 CRC Press published the “Concrete Repair to EN 1504” as paperback. This issue does not differ in terms of content from the hardback publication of 2014. Like the previous version, the book covers both detailed background information on repair procedures of reinforced concrete structures and provides a reference work for technicians and people who are involved with the maintenance of these structures, according to EN 1504.
The book presents a high number of figures and tables, i.e., approximately one illustration per page.
For readers who prefer a more comfortable to handle paperback, the book is recommended; however, the hardback from 2014 is still up‐to‐date.
Welcome to the second symposium on Knowledge Exchange for Young Scientists (KEYS) in Accra, Ghana 7th – 9th June 2016. This symposium is part of a three phase series organised by BAM, and funded by VolkswagenStiftung. The KEYS symposia series offers a platform whereby young African scientists can get together with peers from Germany as well as with experienced academic engineers, industry specialists and scientists from across the globe for better implementation of research analysis in their respective fields of study. This primarily provides the opportunity to obtain further knowledge in the demand for the home-base innovation and growth of the education sector. It will also provide an opportunity to network with peers and gain relevant and objective knowledge. Therefore, the symposium offers adequate training to young scientists as well as gives an opportunity to network with key players in the cement and concrete industry, which will facilitate the fundamentals of knowledge transfer.
This second symposium focuses on solid waste management and importance of valorisation of suitable by-products for utilisation in the cement and concrete industry. Today, all over the world we can no longer draw on abundant resources, and more frequently, we need to develop innovative concepts for better and more sustainable construction. This change process needs international and interdisciplinary approaches. Hence, the symposium is seen as a spark for the generation of ideas and visions, how concrete construction can become more globally sustainable based on locally tailored concepts. The symposium includes keynote lectures from 9 international keynote speakers and technical papers from 22 young scientists, who were selected out of a high number of applicants based on the excellence of their scientific writing. The presentations of all participants as well as keynote lectures are represented in these proceedings.
We would like to thank all participants for their valuable contribution to the symposium. We are blessed to receive tremendous input from the distinguished keynote speakers and we thank them for their attendance. Last but not least, we would like to acknowledge the funding body, VolkswagenStiftung, for their support. We hope you enjoy the symposium and find your engagement valuable with the entire team in sustaining your professional development in the global world of cement and concrete.
Welcome to the first symposium on Knowledge Exchange for Young Scientists (KEYS) in Dar es Salaam, Tanzania, 9th – 11th June 2015. This symposium is part of a three phase series organised by BAM, and funded by VolkswagenStiftung. Each symposium will focus on relevant themes in the construction sector and will include adequate training as well as offer an opportunity to participate in informal discussions between key players and young scientists, which will facilitate the fundamentals of knowledge transfer.
Our world of cement and concrete faces tremendous challenges for the future. Without doubt cement-based materials will remain the most widely used construction materials in the world. Concrete can be made available everywhere in the world, and it is more sustainable than other materials. Nevertheless, in order to become even more sustainable, we need to find solutions to reduce CO2 generation for the cement production, to quickly solve problems of housing and infrastructures, and to cope with ever increasing customer needs in terms of performances.
There is no global optimum solution for concrete. Best concrete practices always has to be found locally and regionally based on raw materials, supply chains, and construction needs, but it can be inspired by other regions. In order to tackle the future challenges and build more innovative with concrete, we need to enhance interdisciplinary engineering skills and create networks between future decision makers.
Therefore, the KEYS symposia series offers a platform whereby young African scientists can get together with peers from Germany as well as with experienced academic engineers, industry specialists and scientists from across the globe for better implementation of research analysis in their respective fields of study. This primarily provides the opportunity to obtain further knowledge in the demand for the home-base innovation and growth of the education sector. It will also provide an opportunity to network with their peers and gain relevant and objective knowledge.
The theme for this first symposium is sub-Saharan African standards for cement and concrete research – raw materials, quality control and maintenance of cementitious products. The symposium is divided into 8 sections and includes presentations from 9 international keynote speakers and 22 young scientists, who were selected out of a high number of applicants based on the excellence of their scientific writing.
We would like to thank all participants for their valuable contribution to the symposium. We are blessed to receive tremendous input from the distinguished keynote speakers and we thank them for their attendance. Last but not least, we would like to acknowledge the funding body, VolkwagenStiftung, for their support. We hope you enjoy the symposium and find your engagement valuable with the entire team in sustaining your professional development in the global world of cement and concrete.
A probabilistic approach for finite element analysis (FEA) for tunnel linings exposed to the nominal fire is presented. The probabilistic FEA accounted for the uncertainties distributions tied to the conductivity and specific heat as well as of the compressive strength, tensile strength, Young’s modulus, and ultimate strain in compression. To get an understanding on the influence of different probability density functions on the distribution of maximum displacements of the tunnel lining, a sensitivity analysis was performed. Four sets of FEAs were carried out with different probability distributions of the conductivity, the specific heat, and the compressive strength of the concrete, respectively. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters which describe each analysis case. A reliability analysis was executed considering a limit state function based on the temperature-dependent ultimate strain. The results show that, depending on the distribution adopted, the standard deviation of the maximum displacements can vary up to 47,4% of the minimum standard deviation. The large standard deviation is associated with the possibility of a greater displacement and, hence, to a structure more vulnerable to fire.
A probabilistic finite elements analysis (FEA) of a tunnel lining subject to fire is presented. The probability distributions of the parameters related to the thermal analysis was considered in order to study the variability of the results and to carry out a reliability analysis. This assessment considered as random variables the thermo-mechanical properties of the concrete, the maximum heat release rate (HRR), the duration of the period of maximum HRR, the convective coefficient, the emissivity at the surface exposed to the fire, the air velocity within the tunnel, and the initial fire radius. The temperature-time curve was described by a correlation. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters to each analysis case. The definition of a limit state function based on the punctual strain status has permitted to carry out a reliability analysis.
Probabilistic thermo-Mechanical analysis of a concrete tunnel lining subject to fire The probability distributions of the parameters related to the thermal analysis was considered in order to study the variability of the results and to carry out a reliability analysis. This assessment considered as random variables the thermo-mechanical properties of the concrete, the maximum heat release rate (HRR), the duration of the period of maximum HRR, the convective coefficient, the emissivity at the surface exposed to the fire, the air velocity within the tunnel, and the initial fire radius. The temperature-time curve was described by a correlation. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters to each analysis case. The definition of a limit state function based on the punctual strain status has permitted to carry out a reliability analysis.
For concrete production aggregates, cement and water are mixed together and after 28 days of hydration a porous and multiphase material is formed. To consider the heterogeneity of concrete a 2D scanning system is used. The coarse aggregates (limit > 2 X d ) can be excluded. laser spot The remaining content is a mixture of flour grains and cement particles (micro heterogeneity). Harmful species like chlorides may penetrate together with water through the capillary pore space. A quantification of Cl regarding to the cement content only (European standard EN 206) is necessary for the damage assessment. A LIBS system operating with a NdCr:YAG laser (pulse energy of 3 mJ, a wavelength of 1064 nm, a pulse width of 1.5 ns, a repetition rate of 100 Hz) and two Czerny-Turner spectrometer (UV and NIR range) have been used.
Laser-induced breakdown spectroscopy (LIBS) is a combination of laser ablation and optical emission spectroscopy. Due to the possibility of direct measurements on the sample surface with a minimum of sample preparation investigations of building materials can be conducted quite fast. In combination with a scanning technique (translation stage or scanning mirrors head) 2D element distributions of harmful species like chlorides and alkalis are evaluated with a sub-mm resolution. By scanning a surface of typically 100 mm x 100 mm the heterogeneity of the material may be considered. LIBS is capable to identify hot spots in element concentration with a resolution of 0.1 mm or even smaller. A LIBS-system for the on-site application on building materials is, in cooperation with system developers and companies which will use this technique for investigation on real structures, under test at BAM. We present an example. Further work will focus on providing guidelines to establish LIBS as a standard procedure for chemical investigations of building materials.