@article{PatzeltErfurtLudwig,
  author    = {Patzelt, Max and Erfurt, Doreen and Ludwig, Horst-Michael},
  title     = {Quantification of cracks in concrete thin sections considering current methods of image analysis},
  series = {Journal of Microscopy},
  volume    = {2022},
  journal   = {Journal of Microscopy},
  number    = {Volume 286, Issue 2},
  doi       = {10.1111/jmi.13091},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220811-46754},
  pages     = {154 -- 159},
  abstract  = {Image analysis is used in this work to quantify cracks in concrete thin sections via modern image processing. Thin sections were impregnated with a yellow epoxy resin, to increase the contrast between voids and other phases of the concrete. By the means of different steps of pre-processing, machine learning and python scripts, cracks can be quantified in an area of up to 40 cm2. As a result, the crack area, lengths and widths were estimated automatically within a single workflow. Crack patterns caused by freeze-thaw damages were investigated. To compare the inner degradation of the investigated thin sections, the crack density was used. Cracks in the thin sections were measured manually in two different ways for validation of the automatic determined results. On the one hand, the presented work shows that the width of cracks can be determined pixelwise, thus providing the plot of a width distribution. On the other hand, the automatically measured crack length differs in comparison to the manually measured ones.},
  subject      = {Beton},
  language  = {en}
}
@article{MuellerLudwigTangeHasholt,
  author    = {M{\"u}ller, Matthias and Ludwig, Horst-Michael and Tange Hasholt, Marianne},
  title     = {Salt frost attack on concrete: the combined effect of cryogenic suction and chloride binding on ice formation},
  series = {Materials and Structures},
  volume    = {2021},
  journal   = {Materials and Structures},
  number    = {issue 54, article 189},
  doi       = {10.1617/s11527-021-01779-7},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211207-45392},
  pages     = {1 -- 16},
  abstract  = {Scaling of concrete due to salt frost attack is an important durability issue in moderate and cold climates. The actual damage mechanism is still not completely understood. Two recent damage theories—the glue spall theory and the cryogenic suction theory—offer plausible, but conflicting explanations for the salt frost scaling mechanism. The present study deals with the cryogenic suction theory, which assumes that freezing concrete can take up unfrozen brine from a partly frozen deicing solution during salt frost attack. According to the model hypothesis, the resulting saturation of the concrete surface layer intensifies the ice formation in this layer and causes salt frost scaling. In this study an experimental technique was developed that makes it possible to quantify to which extent brine uptake can increase ice formation in hardened cement paste (used as a model material for concrete). The experiments were carried out with low temperature differential scanning calorimetry, where specimens were subjected to freeze-thaw cycles while being in contact with NaCl brine. Results showed that the ice content in the specimens increased with subsequent freeze-thaw cycles due to the brine uptake at temperatures below 0 °C. The ability of the hardened cement paste to bind chlorides from the absorbed brine at the same time affected the freezing/melting behavior of the pore solution and the magnitude of the ice content.},
  subject      = {Beton},
  language  = {en}
}
@article{KleinerRoesslerVogtetal.,
  author    = {Kleiner, Florian and R{\"o}ßler, Christiane and Vogt, Franziska and Osburg, Andrea and Ludwig, Horst-Michael},
  title     = {Reconstruction of calcium silicate hydrates using multiple 2D and 3D imaging techniques: Light microscopy, μ-CT, SEM, FIB-nT combined with EDX},
  series = {Journal of Microscopy},
  volume    = {2021},
  journal   = {Journal of Microscopy},
  publisher = {John Wiley \& Sons Ltd},
  address   = {Oxford},
  doi       = {10.1111/jmi.13081},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220106-45458},
  pages     = {1 -- 6},
  abstract  = {This study demonstrates the application and combination of multiple imaging techniques [light microscopy, micro-X-ray computer tomography (μ-CT), scanning electron microscopy (SEM) and focussed ion beam - nano-tomography (FIB-nT)] to the analysis of the microstructure of hydrated alite across multiple scales. However, by comparing findings with mercury intrusion porosimetry (MIP), it becomes obvious that the imaged 3D volumes and 2D images do not sufficiently overlap at certain scales to allow a continuous quantification of the pore size distribution (PSD). This can be overcome by improving the resolution and increasing the measured volume. Furthermore, results show that the fibrous morphology of calcium-silicate-hydrates (C-S-H) phases is preserved during FIB-nT. This is a requirement for characterisation of nano-scale porosity. Finally, it was proven that the combination of FIB-nT with energy-dispersive X-ray spectroscopy (EDX) data facilitates the phase segmentation of a 11 × 11 × 7.7 μm3 volume of hydrated alite.},
  subject      = {Zementklinker},
  language  = {en}
}
@article{LeNguyenLudwig,
  author    = {Le, Ha Thanh and Nguyen, Sang Thanh and Ludwig, Horst-Michael},
  title     = {A Study on High Performance Fine-Grained Concrete Containing Rice Husk Ash},
  series = {International Journal of Concrete Structures and Materials},
  journal   = {International Journal of Concrete Structures and Materials},
  doi       = {10.1007/s40069-014-0078-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170425-31477},
  pages     = {301 -- 307},
  abstract  = {Rice husk ash (RHA) is classified as a highly reactive pozzolan. It has a very high silica content similar to that of silica fume (SF). Using less-expensive and locally available RHA as a mineral admixture in concrete brings ample benefits to the costs, the technical properties of concrete as well as to the environment. An experimental study of the effect of RHA blending on workability, strength and durability of high performance fine-grained concrete (HPFGC) is presented. The results show that the addition of RHA to HPFGC improved significantly compressive strength, splitting tensile strength and chloride penetration resistance. Interestingly, the ratio of compressive strength to splitting tensile strength of HPFGC was lower than that of ordinary concrete, especially for the concrete made with 20 \% RHA. Compressive strength and splitting tensile strength of HPFGC containing RHA was similar and slightly higher, respectively, than for HPFGC containing SF. Chloride penetration resistance of HPFGC containing 10-15 \% RHA was comparable with that of HPFGC containing 10 \% SF.},
  subject      = {Hochfester Beton},
  language  = {en}
}