Petr Bouška

Experimental Investigation of Mechanical Properties of Textile Glass Reinforcement

Mechanical tests were performed at the Klokner Institute on samples of a textile glass reinforcement. These tests will be used for determining the modulus of elasticity of textile glass reinforcements and for assessing the maximal stress that the samples will withstand. Both of these quantities are required for further modeling of the structures and for designing elements made from textile reinforced concrete (TRC). The tests were carried out on a total of 10 samples made from a single piece of 2D net (produced by V. FRAAS, GmbH, Germany). The tests were carried out on AR-glass reinforcement (alkali - resistant glass) textile glass with 2400 TEX [g/km] fineness, which is often supplied with dimensions of 1 x 2 m. The first 5 samples were prepared in the direction of the warp (the direction of the load-bearing reinforcement), and the remaining 5 samples were prepared from the transverse direction (the direction of the weft). These samples were loaded by a constant force increasing up to collapse. Then the modulus of elasticity of the textile glass reinforcement and the stress at the strength limit were determined from the monitored data.

Degradation of Laminated Glass as Result of Increased Temperature

The degradation of laminated glass as a result of increased temperature has become one of the important problem of reconstructions and designs of new glass structures, for instance high-rise buildings that are exposed to the impacts of an intensive heating caused e. g. by sunshine. The temperatures during heating can reach very high values, commonly from 60 to 70 °C. The effect of heating was simulated using the thermal chamber where the glass panes with the size of 120 x 1100 mm were heated. The deformation course under the increase of temperature was continually monitored by a measuring unit. In total six types of foils joining particular layers of glass were examined. In this paper the experimentally gained results are compared with a numeric computer analysis and the particular kinds of interlayers are evaluated using the loss of shear interaction.

Study of Corrosion Damage of Glass Fibers in Textile Fiberglass Reinforcement under Expositions Simulating Concrete Environment

The main point of this paper is to assess the level of corrosion damage of the composite textile fiberglass reinforcement in environments that simulate the concrete pore solution by the techniques of FT-IR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) as well as EDS (scanning electron microscopy). Effect of corrosion on the tensile strength segmented textile glass fiber was tested and also it was investigated specific type of protective organic coating on glass fiber. The results express the evidence of local corrosion damage on the examined samples just at pH 13.5, and on the contrary high stability in the environment simulating carbonated concrete and concrete contaminated by chloride anions. The thesis also points on the unevenness of the excluded protective organic coating with localized porosity which relates to the above mentioned corrosion damage.

Textile Concrete in Adverse Conditions

Textile concrete (TRC) is a modern material that has been the subject of many scientific studies over the past two decades. It is a material based on a fine-grained cement-based matrix, fiber reinforced, fabric of acrylic-resistant glass, basalt or carbon reinforcement. The products from this material are thin-walled elements, which can be used, for example, for facade claddings elements, lost formwork, shell structures, garden architecture or for strengthening or repair of existing structural elements. This paper presents some examples of the behavior of glass reinforced textile concrete during exposure to road salts, under load of bending moment, at long-term loading at elevated temperatures, and assessment of glass fiber resistance during exposure simulating concrete pore solution.

Effect of Temperature Increasing on Deformation Properties of TRC

This paper presents a description of the changes in the deformation properties of TRC under a gradual increase in temperature. TRC [1, 2] is a composite material consisting of a fine-grained UHPC matrix and textile glass fibres, known as AR-Glass. A very high load-bearing composite can be produced by combining the high compressive strength of UHPC (approximately 150 MPa) and the high tensile strength of textile glass fibres (about 2200 MPa). Samples 1100 x 120 x 20 mm in size were produced for the experiment. The samples were placed in a thermal chamber and were submitted to a constant load. In the next step, a gradual increase in temperature up to 75oC was simulated using heating cables located on the bottom of the chamber. We monitored the changes in bending in the middle of the span. Since the experiments are very time-consuming, the experiment was also simulated using a numerical model. Finally, there is a qualitative comparison of the two methods.

Experimental Tests of I Profile Made from UHPC Reinforced with Textile Glass Fibres

This abstract is summarizing production and subsequent experimental testing of 3D profile of the symmetrical I shape concrete from UHPC matrix and reinforced with textile glass fibres. Upper and bottom covering strips of this profile are at the outside fibres reinforced with textile glass reinforcement. Position of this reinforcement is fixed in the distance of about 3 mm from outside fibres and is connected with reinforcement of the profile stem located in its axis. Such prepared beams were tested with four-point flexure evenly loaded until fracture. Course of the measurement was continuously recorded by the automatic logger, where mostly increase of the force in relation to deflection in the middle of the span and change of position of supports were recorded. From the recorded data were prepared graphic outputs compared with the same experiments performed on I profile which is not reinforced, i.e. only UHPC matrix, and for comparison also on the profile made from UHPC matrix with use of metal wires. In the conclusion were compared achieved test results. Mainly suitability and loading capacity of individual beam types was compared. Within the experiment were performed supporting tests based on which were determined material characteristics of tested matrix and textile glass reinforcement. Tests were performed in the Klokner Institute within solution of the grant project GACŘ 13-12676S.

Long Term Measuring of Expansions and Contractions of Pre-Stressed Concrete Bridge Structure

The presented paper considers approx. 5 years measurement on concrete railway bridge. The span is 39.875 + 34.877 + 37.000 + 9 x 31.500 m. The total length of the bridge is 443 m. Structure possesses typical three-box cross section. Monitoring was focused on temperature of concrete, temperature of atmosphere in the shade and mainly on measurement of movements of several bearings. Because the monitoring period of bridge structure was approx. 5 year, the probability p = 0.2 (5 years returning period) was chosen in order to compare measured data with standard values according to EN 1991-1-5. Of course, the standard value was assumed without any safety factor for this purpose. The maximal difference of measured and standard values was only 25 mm. This was achieved on the pillar where measured value of displacement range was 135 mm, standard value 160 mm and the dilatation length was 332 m. On the other hand, the minimal difference was only 3 mm on the pillar where measured value was 33 mm, standard value 36 mm and the dilatation length was 75 m. If the approx. 5 years measurement is compared with theoretical value of 5 years return period, the standard procedure cannot be classified as very conservative. It was shown that the long-time measurement is very important for the further development and improvement of the Eurocodes as well as statistical approach, i.e., returning time which shall be taken into account.

Impact of Increased Temperature on Cohesiveness of Textile Glass Reinforcement with UHPC Matrix

The contribution is focused on research results of thin elements with UHPC matrix reinforced by textile glass reinforcement. A set of three test samples with size of 1100 x 120 x 20 mm were produced in laboratories of the Klokner Institute. Using accompanying tests the material characteristics of the concrete matrix and the textile glass reinforcement were determined. This reinforcement is modified by a protective epoxy surface layer, co called coating. The reason of the coating is to prevent a formation and a development of corrosive processes on the reinforcement texture. The samples were tested at four-point bend test in a thermal chamber. The thermal chamber is a space where it is possible to gradually regulate the temperature up to 75 °C under a constant value of a loading. In the course of the temperature increasing is using a measuring unit measured mainly bend in the middle of the span in time and the course of an inner and outer temperature. The impact of the increased temperature on the cohesiveness of the non-conventional reinforcement and the UHPC matrix is evaluated from the monitored data.

Experimental Verification of the Effective Thickness of Laminated Glass

Properties of laminated glass comprising two or more sheets of glass are greatly affected by the composite action of these panes which is influenced by material properties of used interlayer. Generally plastic foil or cast resin is used as the interlayer in lamination process. Laminated glass has been experimentally investigated in the laboratory condition in a four-point bending test on several kinds of interlayers in combination with variable thickness of the annealed glass. This paper establishes the so-called effective bending thickness according to standard method and presents comparisons with experimentally determined values.

Determination of Mechanical Properties of Non-Conventional Reinforcement

Mechanical tests of samples of basalt and textile glass reinforcement were performed within the solution of the research project GAČR 13-12676S and SGS14/171/OHK1/2T/31. These tests were carried out because of the need to establish elementary mechanical quantities that are tensile strength and modulus of elasticity of non-conventional reinforcement. Both of these quantities are required for further modeling of structures and for designing of the elements made from textile reinforced concrete (TRC) as not being provided by reinforcement manufacturers. The tests were carried out on a total of 12 samples of reinforcement where the first 6 samples were made from textile glass reinforcement (AR-G = Alkali-Resistant Glass) and the remaining 6 samples were prepared from basalt reinforcement. The filament sheaf fibers called roving was used for the production of test specimens.