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- ItemFracture parameters of fine-grained composites based on the alkali-activated slag(IOP Publishing, 2018-07-12) Bílek, Vlastimil; Kucharczyková, Barbara; Šimonová, Hana; Kocáb, Dalibor; Keršner, ZbyněkThe paper deals with the experimental determination of fracture parameters of the composites based on the alkali-activated slag (AAS) at different ages. The main aim of the experimental investigation was to verify the effect of the addition of shrinkage reducing admixture (SRA) on the overall progress of length changes and fracture properties during AAS composites ageing. Two AAS composites, which differed only in the presence of SRA, were prepared for the purpose of experiments. The mechanical fracture parameters were determined using evaluation of fracture tests carried out on 40 × 40 × 160 mm beam specimens with an initial central edge notch. The monitored parameters were modulus of elasticity, effective fracture toughness and specific fracture energy. These parameters were determined at the age of 3, 28 and 90 days. The obtained results are supplemented by the results of relative length changes measurements performed on both studied composites.
- ItemTesting the Influence of the Material Bonding System on the Bond Strength of Large-Format Tiles Installed on Concrete Substrate under Mechanical Loading(MDPI, 2020-07-17) Topolář, Libor; Kocáb, Dalibor; Šlanhof, Jiří; Schmid, Pavel; Daněk, Petr; Nováček, JaroslavThe paper describes an experiment focusing on the way the material system influences the bond strength of large-format tiles installed on concrete substrate during mechanical loading under conditions that correspond to real-life application. This involves a controllable mechanical load applied over an area of a test model while observing its condition using non-destructive methods (ultrasonic pulse velocity test, acoustic emission method, strain measurement, and acoustic tracing). The model consisted of a concrete slab onto which were mounted four different systems with large-format tiles with the dimensions of 3 m x 1 m. The combinations differed in the thickness of the tile, the adhesive, and whether or not a fabric membrane was included in the adhesive bed. The experiment showed that the loading caused no damage to the ceramic tile. All the detected failures took place in the adhesive layer or in the concrete slab.
- ItemTesting an Impedance Non-destructive Method to Evaluate Steel-Fiber Concrete Samples(DE GRUYTER POLAND SP ZOO, 2018-03-01) Komárková, Tereza; Fiala, Pavel; Steinbauer, Miloslav; Roubal, ZdeněkSteel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to the development of cracks. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite have been distributed evenly. The current methods to evaluate the distribution and concentration of a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses tests related to the evaluation of the density and orientation of fibers in a composite material. Compared to the approaches used to date, the proposed technique is based on the evaluation of the electrical impedance Z in the band close to the resonance of the sensor-sample configuration. Using analytically expressed equations, we can evaluate the monitored part of the composite and its density at various depths of the tested sample. The method employs test blocks of composites, utilizing the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of between f=3 kHz and 400 kHz.
- ItemDestructive and non-destructive assessment of the frost resistance of concrete with different aggregate(IOP Publishing, 2018-07-12) Kocáb, Dalibor; Kucharczyková, Barbara; Daněk, Petr; Vymazal, Tomáš; Hanuš, Petr; Halamová, RomanaThe paper focuses on determining the frost resistance of concrete using selected destructive and non-destructive test methods. The experiment was performed with four specially made concretes, which differed only in the origin of sand and coarse aggregate. The primary outcome of the experiment are the differences in frost resistance as measured by different methods. In addition, it briefly describes the influence that the choice of aggregate has on the frost resistance of concrete.
- ItemQuality Control of the Anchoring of Steel Bridge Barriers by Non-Destructive Testing(MDPI, 2020-01-07) Komárková, Tereza; Láník, Jaromír; Anton, OndřejTraffic barriers represent one of the basic road safety features. There are several types of traffic barriers based on the material from which they are made of and their location. Bridge structures are usually fitted with steel barriers. A steel barrier is, in fact, a relatively complex system linking individual steel elements, which, as a whole, has to meet the requirements given by normative regulations. In order for the steel barriers to fulfill their function and prevent the catastrophic consequences of traffic accidents, it is absolutely necessary to ensure their correct installation on the bridge structure. It seemed until recently that carrying out quality inspections of steel barriers installation, i.e., their anchoring into the concrete ledges, was a relatively complicated time- and money-consuming process, and that is why inspections of the correct anchoring installation in new or existing barriers were not carried out as standard. This paper thoroughly describes in detail the non-destructive ultrasonic pulse method, with which the anchoring of steel barriers on selected bridge structures is being checked. From the measurements and statistical evaluation of the results, it is apparent that carrying out inspections of the anchoring of these road safety features should be considered routine, and at the same time, the inspection of anchoring quality should be required by law in order to ensure the safety of road traffic.