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Characterization of Božanov sandstone: pilot fracture tests
Kumpová, I. ; Rozsypalová, I. ; Vavro, Leona ; Vavro, Martin ; Keršner, Z.
The aim of this paper is a characterization ofsandstone from Božanov quarry near Broumov, Czech Republic,by means of the pilot fracture tests. Five drill-core test specimens withnominal diameter of 50mm and lengths of 100 and 125mmwere provided by an initial chevron type notch. Specimens were loaded in the configuration of the three-point bending as a displacement driven experimentusing LabTest 6.250 equipment in the laboratory of the Institute of Building Testing, Faculty of Civil Engineering, Brno University of Technology. The load versus displacement diagrams were used to quantify the basic mechanical fracture parameters of the studied sandstone: modulus of elasticity, fracture toughness, toughness, and specific fracture energy.
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X-ray micro-tomography characterization of voids caused by three-point bending in selected alkali-activated aluminosilicate composite
Kumpová, Ivana ; Rozsypalová, I. ; Keršner, Z. ; Rovnaníková, P. ; Vopálenský, Michal
This paper deals with the pilot characterization of a special alkali-activated aluminosilicate composite composed of waste brick powder, brick rubble and a solution of potassium water glass. Fracture tests were conducted on the specimens via three-point bending and fracture parameters were evaluated. Selected specimen was investigated using micro-tomography to supplement the results with visual information about the inner structure of this newly designed material before and after the mechanical loading. Tomographic measurements and image processing were conducted for a qualitative and quantitative assessment of changes in the internal structure with an emphasis on the calculation of porosimetric parameters and visualization of the fracture surface. Fractal dimension of fracture surface was estimated.
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Evaluation of self-healing in concrete by means of analytical techniques
Aspiotis, K. ; Sotiriadis, Konstantinos ; Kumpová, Ivana ; Mácová, Petra ; Badogiannis, E. ; Tsivilis, S.
In the present work, the self-healing process in concrete was evaluated using analytical techniques. For this purpose, two concrete mixes of different composition (one used as reference) were prepared with a W/B of 0.45. The self-healing process was triggered by the introduction in the concrete mix of a commercial expansive admixture (calcium sulfo-aluminate), two dicarboxylic acids, and sodium carbonate salt. After 28 days curing in water, the specimens were artificially cracked (crack width ≈ 400 μm) and then again water-cured for 40 days until self-healing occurred. The progress of self-healing was investigated with a stereo-microscope at 40, 50 and 60 days. The efficiency of the process was evaluated using micro-Raman spectroscopy and X-ray micro-computed tomography (XmCT). Significant reduction in the crack width was observed as a result of filling the crack with calcite generated during the self-healing process. In some cases, the crack was completely healed. The experimental methodology used provided new insights into the evolution of the self-healing phenomenon in concrete.
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Fracture Parameters of AAAS composites with ceramic precursor
Šimonová, H. ; Rozsypalová, I. ; Kumpová, Ivana ; Trčka, T. ; Frantík, P. ; Rovnaníková, P. ; Keršner, Z.
The paper deals with alkali-activated aluminosilicate composites based on ceramic precursors with respect to their characterization by fracture-mechanical parameters. Three composites made of brick dust as a precursor and alkaline activator with silicate modulus Ms = 1.0, 1.2 and 1.4 were investigated. After 28 days of maturation, specimens with nominal dimensions of 40 × 40 × 160 mm were provided by an initial notch to 1/3 of the body height in the middle of the span. At least 6 samples were tested from each composite. Specimens were subjected to three-point bending tests during which force vs. deflection at midspan (F–d) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. By processing these diagrams, the values of the static modulus of elasticity, the effective fracture toughness (including its initiating component) and the specific fracture energy were determined using the effective crack model, Work-of-Fracture method, and Double-K fracture model. After the fracture experiments had been performed, compressive strength values were determined for informational purposes from one part of each specimen that remained after testing. All evaluations included the determination of arithmetic means and standard deviations. To obtain information about the internal structure of composites before and after mechanical testing, the selected body was examined by micro-tomography. Tomographic measurements and image processing were performed for qualitative and quantitative evaluation of internal structure changes with an emphasis on the calculation of porosimetric parameters as well as visualization of the fracture process zone. The fractal dimension of fracture objects was determined.
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Possibilities of using 4D computed tomography in fracture tests
Kumpová, Ivana ; Fíla, Tomáš ; Koudelka, Petr ; Rozsypalová, I. ; Keršner, Z. ; Kytýř, Daniel ; Vopálenský, Michal ; Vavřík, Daniel ; Vyhlídal, M. ; Drdácký, Miloš
The paper presents the study of the internal structure and fracture properties of selected quasi-brittle building materials subjected to temperature changes and the possibility of applying the method combining bending fracture tests and time-dependent computed tomography (4D CT). The tested specimens were subjected to hightemperature effects and subsequently tested by a four-point bending during 4D CT. Thus, 3D image information was obtained in different phases of loading and material damage. Comparative compression strength measurements were also performed. These results are in good agreement
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Large-area scans of paintings with high resolution
Vopálenský, Michal ; Kumpová, Ivana
The aim of the measurement was to obtain the radiographs from historical paintings from the Faculty of Restoration of the University Pardubice. Due to the dimensions of the paintings (up to 90 x 110 cm) it was necessary to develop a suitable measurement procedure for successive scanning of the paintings in the TORATOM device. The resulting data are important for the planning of the restoration processes of the paintings and can help to discover otherwise invisible details, like underpaintings etc.
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Historical lingerie: 18th century corset
Kumpová, Ivana ; Vopálenský, Michal
The work was focused on the methodology using X-ray tomographical imaging for the exploration of the textile-based historical artifacts. The 18th-century corset was investigated by this method. The inspection was conducted to reveal the production technology, design solution, decoration and possible damage in the front area where the whalebones converge. The computed tomography performed on the TORATOM device enabled visualisation of the internal structure of the area of interest with high precision. Sewing details and details of the composition of different material layers are well visible. Fractures and frayed ends of the whalebones were observed. In the area of interest, it is possible to distinguish several materials used for padding of the plastic parts.
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Instrumentation of four-point bending test during 4D computed tomography
Kytýř, Daniel ; Fíla, Tomáš ; Koudelka_ml., Petr ; Kumpová, Ivana ; Vopálenský, Michal ; Vavro, Leona ; Vavro, Martin
High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of non-homogeneous materials subjected to mechanical loading. This experimental method requires implementation of specifically designed loading devices to X-ray imaging setups. In case of bending tests, our background research showed that no commercial solution allowing for reliable investigation of so called fracture process zone in quasi-brittle materials is currently available. Thus, this paper is focused on description of recently developed in-situ four-point bending loading device and its instrumentation for testing of quasi-brittle materials. Proof of concept together with the pilot experiments were successfully performed in a CT scanner TORATOM. Based on results of the pilot experiments, we demonstrate that crack development and propagation in a quasi-brittle material can be successfully observed in 3D using high resolution 4D micro-CT under loading.
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