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Open access

Pavel Škvára, Julia Kezmanová, Csilla Mišl’anová and Andrea Vojs Staňová

Abstract

The beneficial effects of green foods on human health are well known. These benefits are mainly due to polyphenol content. The aim of this work was the development and utilization of an advanced mass spectrometry (MS) technique combined with high-performance liquid chromatography (HPLC) for the analysis and identification of polyphenolic compounds in green foods. HPLC-ESI-MS/MS analyses of selected extracts prepared from various types of green food (Urtica dioica L. and Allium ursinum L.) and their polyphenolic profiles were performed by an LCMS-IT-TOF analyzer equipped with electrospray ionization. HPLC separation was conducted by a Kinetex XB-C18 column (100µ2.1 mm; 2.6 µm) using gradient elution (water + 0.1% formic acid: acetonitrile + 0.1% formic acid) with a flow rate of 0.2 mL/min. The MS1-MS3 analyses were performed within a 50-1000 m/z range in both positive and negative ionization modes. The total analysis time was 20 minutes and injected volumes were 2 µL and 5 µL, respectively

Open access

Alisa Machner, Petter Hemstad and Klaartje De Weerdt

Abstract

Hydrated Portland cement paste exposed to a NaCl solution was acidified by adding HCl in small steps, gradually lowering the pH. The chloride binding of the cement paste changed as a function of the pH. For the range of pH from 13.2 to 12.2, decreasing pH resulted in a considerable increase in the chloride binding. At a pH of 11, the cement paste showed almost no chloride binding. In order to explain the changes in chloride binding upon lowering the pH, the phase assemblage was investigated with SEM-EDS, TGA and XRD and compared to a thermodynamic modelling.

Open access

Nikodem Wróbel, Michał Rejek and Grzegorz Królczyk

Abstract

The purpose of this study is to form and test inseparable tight joints, commonly used in the construction of heat exchangers, by crimping operation on designed prototype stand. Crimped joints are made by tools in form of cones with two types of shapes, each of the designed tools have got identical forming angle. This study uses two types of connecting blocks and plates, differing in diameters of hole and flange. Elaboration contains a case study of joints being made by the stand, which in addition to the crimping operations for some cases were glued or brazed. The article presents the features of the formed joints, by examining them by destructive testing: Micrography, tensile strength test, and non-destructive testing: Leakage test. The examined elements have been made of aluminum 6060, which is well suited to indirect or direct operations of forming joints for all kinds of coolers or condensers. Elaborated tests and studies in this study allowed to state, that joining the connection block to plate with the small diameter, was more energy-consuming than in sample sets with bigger diameter, use of glue increasing the strength of the joints by 20%, significant strength increase can be obtained after mechanical clinching with brazing operation or modification of geometrical shape of the jaws

Open access

Magnus Döse and Johan Silfwerbrand

Abstract

The second largest cause of lung cancer is related to radon (222Rn) and its progenies in our environment. Building materials, such as concrete, contribute to the production of radon gas through the natural decay of 238U from its constituents. The Swedish Cement and Concrete Research Institute (CBI) has examined three concrete recipes where only an additive as well as fly ash were added as single constituents to a reference recipe and compared to a reference concrete. The inputs of an additive as well as a supplementary cementitious material (fly ash) were made as a mean to investigate their potential influence on the radon exhalation rates of the concrete. Measurements were performed with an ATMOS 33 ionizing pulsation chamber for at least five different occasions for each recipe during a 22 month period. The results indicate a reduction of the exhalation rate by approximately 30-35 % for each altered recipe. This means roughly 1.5-2 mSv per year decrease in effective dose to a human using an additive or a supplementary cementitious material such as fly ash in relation to the investigated standard concrete.

Open access

Mohammad H. Baghban, Mahdi Kioumarsi and Sotirios Grammatikos

Abstract

Cement-based materials are the most consumed materials in the construction industry. Low or high thermal conductive cement-based materials are of interest in applications such as embedded floor heating systems, building envelopes or structural elements. This paper describes prediction models for thermal conductivity of cementitious composites by considering different variables such as constituent materials, porosity and moisture content. The presented prediction models may be used for thermal conductivity based mix design of cementitious materials. Based on the desired accuracy, different solutions are proposed.

Open access

Frederik Stefanski and Bartosz Minorowicz

Abstract

This paper is focused on the open loop control of a piezoelectric tube actuator, hindered by a strong hysteresis. The actuator was distinguished with 22 % hysteresis, which hinders the positioning of piezoelectric actuator. One of the possible ways to solve this problem is application of an accurate analytical inversed model of the hysteresis in the control loop. In this paper generalized Prandtl-Ishlinskii model was used for both modeling and open loop control of the piezoelectric actuator. Achieved modeling error does not exceed max. 2.34 % of the whole range of tube deflection. Finally, the inverse hysteresis model was applied to the control line of the tube. For the same input signal (damped sine 0.2 Hz) as for the model estimation the positioning error was max. 4.6 % of the tube deflection. Additionally, for a verification reason three different complex harmonic functions were applied. For the verification functions, still a good positioning was obtained with positioning error of max.4.56 %, 6.75 %and5.6%of the tube deflection.

Open access

Tobias Danner and Mette Rica Geiker

Abstract

This paper presents results from investigations on the long-term influence of concrete surface and crack orientation on ingress in cracks. Five reinforced concrete structures from Norway exposed to either de-icing salts or seawater have been investigated. Concrete cores were taken with and without cracks from surfaces with vertical and horizontal orientation. Carbonation in cracks was found on all de-iced structures, and a crack on a completely horizontal surface appeared to facilitate chloride ingress. Ingress of substances from seawater was found in all cracks from marine exposure. However, the impact of cracks on chloride ingress was unclear. Horizontal cracks on vertical surfaces appeared to facilitate self-healing.

Open access

Nadia Al-Ayish, Otto During, Katarina Malaga, Nelson Silva and Kjartan Gudmundsson

Abstract

Addition of fly ash or GGBS in concrete has shown to increase the durability and thus the service life of concrete structures exposed to chlorides. Currently, the durability relies on regulations, which beside a minimum cover thickness also put constraint on amount and type of SCM in different environments. Swedish regulations do not, however, consider the actual durability of different binders. As a consequence, a LCA might be misleading. This paper investigates the climate impact of concrete with SCM in chloride environment. Current prescriptive design approach is compared with a performance based service life approach and applied to bridge parts.

Open access

Konrad Łyduch and Wojciech Gęstwa

Abstract

The paper presents the influences of nanofluids, which are used in hardening process, to dimension changes, hardness and microstructure of hardened construction of steel samples. An analysis was also carried out with the use of English methods of cooling abilities of nanofluids environments based on water, solid nanoparticles of Al2O3 and ammoniac water. The results of this experiment show, that only one of specific dimensions of cooled samples, in the distilled water, changed for about 9%, but when using nanofluids this change was smaller. The hardness of alloy materials got a few percent more when nanofluids were used in comparasion to using the distilled water. The gained results allow to conclude the positive influence of nanofluids on parameters of the hardened materials.

Open access

Richard Malm

Abstract

In the planned Swedish repository for spent nuclear fuel, plugs are designed to close the deposition tunnels. The outer part of these plugs consists of a concrete dome made with self-compacting-concrete, designed to have low pH to reduce negative effects on the bentonite clay buffer. A full-scale test has been performed to evaluate the performance of the plug, to test the installation and to verify underlying design assumptions. In this paper, the behaviour of the concrete dome is evaluated based on measurements, from casting the concrete until it was subjected to 4 MPa hydrostatic water pressure.