Papers by Keyword: Non-Destructive Methods

Abstract: The feasibility of determining the extent of damage in fibered concrete after being subjected to high temperatures, using non-destructive methods was investigated. The study was conducted on four concrete mixtures with different fiber types. The specimens underwent a curing process at 23 °C before being exposed to different high temperatures of 400 °C, 600 °C, and 800 °C. After cooling to ambient temperature, various non-destructive tests including ultrasonic pulse velocity testing (UPV), the resonance frequency test (RF), the dynamic modulus of elasticity (Ed), the thermal conductivity test (λ), and Schmid Rebound Hammer (SRH), were performed. To evaluate the sensitivity of non-destructive techniques to assess the damage of fiber-reinforced concrete, the Lemaitre coefficient was used as a variable to describe the extent of the damage. The results indicated that the highest damage levels were obtained through the modulus of elasticity technique regardless of the type of concrete mixture or temperature exposure. There was also a potential agreement found between thermal and ultrasonic methods in evaluating the thermal degradation of concrete.

Abstract: This paper deals with the comparison of non-destructive methods of measuring modulus of elasticity by ultrasonic pulse velocity method and impact resonance method. Main research is focused on scattering of measured data, where by different volunteers were used the methods mentioned above on same test sample. This paper does not deal with the conversion relationships between individual methods, but it outlines the suitability of the chosen method in participation with the nature of samples, the difficulty of measurement and the expected reproducibility and interpretability of the measured data.

Abstract: Design, preparation and testing of fibre-cement composites are a task of wide range of research workplaces and universities in our country and abroad. However, a question on homogeneity of all cement matrix components and mainly optimal dispersion of fibre reinforcement in a mixture has not been yet solved sufficiently. Within testing of properties of such designed composites there is usually a realized fact, that variability of these properties is distinctive mainly for the reason of uneven dispersion of commonly used fibres in a whole matrix volume. Elimination of this phenomenon could be achieved by means of a design of the optimal homogenization process of dry mixture components with fibre reinforcement. The aim of research works was to find suitable homogenization techniques, design of mixing process and optimal dosing of individual components. By means of these actions it is possible to achieve the best dispersion of selected fibre types, both metal and non-metal, in fine-grained cementitious matrixes, which is subsequently verified in hardened composites at first by non-destructive and then by destructive methods. Four different fibre-cement mixtures were chosen as representatives for commonly used reinforcement in fibre-cement composites and test specimens with a thickness of 40 mm were prepared using processes suitable for the specific fibre reinforcement. At the first stage non-destructive testing by means of ultrasound waves was carried out at first on a compact test slab with dimensions 500 x 500 x 40 mm and subsequently on individual test specimens with dimensions 250 x 40 x 40 mm, cut from the test slab according to a designed pattern. At the second stage destructive testing of test specimens was performed, mainly evaluation of flexural strength with 4-point bending and subsequently preparation of thin sections from the failure area for observation by means of polarizing microscopy. A purpose of all these research works is finding of correlation between testing by means of destructive and non-destructive methods.

Abstract: Main target of this study is a comparison of material properties of plasters, which were obtained with use non-destructive methods and destructive methods and find out relation between them. These parameters were investigated on plasters. In this research the destructive methods were focused in obtain three parameters: the compressive strength, the tensile strength and the modulus of elasticity. For non-destructive testing was used pulse velocity method. Testing was carried out on specifically fabricated test specimens. With this study were obtained relations of the parameters for each type plasters measured with the non-destructive methods and with the destructive techniques. Obtained data were compared and then evaluated. These relations are very important and necessary for possibility to eliminate destructive methods in future.

Abstract: Almost all reinforced concrete structures which are exposed to weather effects are threatened by corrosion. The corrosion of steel elements in structures has an influence on lifetime these constructions and adversely affects their properties. However, the steel in concrete structures is protected against corrosion due to the properties of concrete such as high pH or impermeability, but if the concrete is of poor quality and his protective properties are insufficient the corrosion can occur. A problem causes the action of carbon dioxide which has the effect of lowering the pH below the critical value and thereby accelerating the corrosion.Non-destructive methods such as Impact-echo method offer the possibility of easy and quickly detection of initial damage of structure and thus can prevent the occurrence of permanent damage to the whole construction.This article describes the development of corrosion which is caused by carbonation of the concrete and supported by action of chlorides by using Impact-echo method. The paper presents results obtained on the reinforced concrete samples with one steel rod passing through the center. After carbonation concrete the samples were exposed accelerated controlled degradation in aqueous NaCl solution for 4 months.

Abstract: The paper deals with experimental simulation measuring and the analysis of defect distribution in passenger car tire under dynamic loading. The main reason for detection of defect extension is to recognize an influence of closed air, small bubbles, separations in tire and it is mainly connected with its quality during its service in a vehicle in terms of road safety. This analysis should help constructors to solve critical conditions in tire casing, whether material selection and individual components proportions are suitable and fit or even the whole construction of tire casing is suitable. The reason for detection of internal defects in tire casing is to avoid the wear of those tires which already contain some internal defects and already recognised separations, which could propagate during the movement of vehicles. This is closely connected with the occurrence of tire destruction and the main purpose is to prevent its critical status and later vehicle crash and human life menace.

Abstract: The experimental, in-situ and laboratory research has manifested a relatively large variance of the physical and mechanical characteristics of historical masonry found e.g. within a masonry wall, a massive masonry pillar etc. Artical presents the evaluation of the experimentally determined physical and mechanical characteristics of masonry members and the binder obtained by sampling specimens and by non-destructive measurements relies on the application of appropriate probabilistic methods.

Abstract: The wood is traditionally been applied as the building material in building and bridge construction. The number of applications of wood in building structures increases in recent years. According with this trend, the emphasis is on the development of diagnostic and monitoring methods for existing wood structures. In the paper, published results of a survey of existing wood structures in relation to the evaluation of qualitative and quantitative characteristics of the investigated structures. There are finally discussed the possibility to reproduce the results of non-destructive measurement relative to evaluate the strength characteristics of wood.