Papers by Keyword: Deterioration

Abstract: Concrete bridges are widely widespread as a main roadway infrastructure. The maintenance and the restoration or renewal of such artefacts are a major concern for the public administration. The reinforced concrete objects are exposed to detrimental atmospheric condition. The deterioration is different for the sixteen highway bridge elements. Some parts are sheltered or directly exposed to the atmospheric events, such as sun, rain, snow, salt spreading, splashing and washing. South-west sides or partially sheltered zones are more susceptible to cyclic temperature and humidity variation. This results in increased carbonation. The North-east sides, especially the curbs, are less carbonated because of enhanced presence of high humidity and are more prone to organic growth. The limit of 0.025 % of chloride content by concrete weight is exceeded in some bridge elements down to 40 mm, apart from the piles. Shoulders and curbs exhibit the highest Chloride content. Lower contents are observed for beams, struts and piles partially sheltered from the direct salt spreading action. A slight correlation exists between high Chloride content and low mean carbonation and depends on the humidity presence. This is observed for the shoulders, the shelves and the curbs, but less for the beams, the piles, the struts and the heads.

Abstract: Ancient archaeological sites contain numerous pottery objects that suffered from different deterioration factors. This study aims to use different analytical methods to study the chemical and mineralogical composition and identification of deterioration aspects of some ancient Egyptian pottery jars from Saqqara excavation. Thus, to explain the deterioration factors' mechanisms and apply the proper conservation methods to the deteriorated pottery jars. AutoCAD, digital microscope, scanning electron microscope (SEM-EDX), and x-ray diffraction (XRD) were used to clarify the preservation states of pottery jars. The results of the investigation revealed that the selected jars suffered from different cracks, salts crystallization, some surface black spots, separation of the slip layer, and heterogeneity in the grains size. XRD analysis revealed that quartz, diopside, illite, muscovite, orthoclase, anorthite, and hematite are the main components of the jars. SEM-EDX analysis showed high concentrations of chlorides and sulfate salts, besides the presence of manganese oxide. Different treatments were performed for the pottery jars include mechanical and chemical cleaning. Additionally, the completion process was done by using a mixture of dental gypsum with grog. Moreover, the consolidation process was achieved by using paraloid B-72.

Abstract: The paper deals with investigation of changes in selected properties of concretes which have been exposed to acid rain. The experiments took place in laboratory under model solution representing acid rain (40 % HNO₃, 60% H₂SO₄) over a period of 7 weeks. The concrete samples investigated were concretes with ordinary Portland cement only as well as concretes of high-portion-mineral-addition-cements as well. Disruptions, cracking and samples' falling apart at the end after 7-week exposure to acid rain were observed by evaluation of visual changes. Based on the determination of the other parameters the results are not so uniform that is why the clear statement of more suitable concrete resistant to acid rain is not given. The assumption that a high-mineral concrete mix would be more suitable for environments exposed to acidic rain was not confirmed in this experiment.

Abstract: In recent years, Al-5Mg alloy thermal spray coatings have been used as an anti-corrosion coating applied for various components of steel structures, in some cases it was covered by the conventional heavy-duty coating. However, the deterioration characteristics of overlapping layers between thermal spray layer and heavy-duty paint coating still not clear. In this study, to compare the anti-corrosion characteristics of the single thermal spray coating and overlapping layers, the accelerated cyclic exposure tests were carried out on specimens with three types of coating layers. To clarify the deterioration characteristics, the cross-cut defect were introduced into specimens, and the EIS measurements, glossiness test, EPMA elemental analyses were conducted on test specimens. The test results indicated that the deterioration of the overlapping layer at the steel base-exposed portion occurs earlier than the case of Al-5Mg thermal spray coating. In addition, the deterioration of thermal spray coating was accelerated by the sealing treatment in specimen with overlapping layers.

Abstract: Abstract: The paper is focused on a system of investigation of hidden parts of historical buildings as footing masonry and subsoil affecting significantly their technical conditions and stability. These impacts are mostly difficult to identify in time and there are often indirect producing differential settlement resulting in development of systems of cracks in the building masonry. Reliable analysis of the building supporting system shall precede any remedial actions or reconstructions. If the demonstration of the above negative impacts on the building becomes visible, it can indicate our late entry in to solving the problems with deterioration of the foundation system. Investigation boring and instrumentation of boreholes for high accuracy 3D displacement monitoring with local levelling system is presented in the paper illustrated by an example of one baroque church of the Broumov group of churches. This activity was followed by analyses of building stones and determination of degree of the footing masonry and subsoil deterioration together with careful input data for numeric modelling estimation.

Abstract: The problem of an assessment of the monitoring of lining condition in the Blast Furnace hearth during its campaign today has no unambiguous solution. Various techniques for the diagnostics have their own merits and demerits [1]. In this paper, characteristics of the diagnostic methods based on the measurements of temperatures in the lining, heat transfer of the cooling system and acoustic effects are considered. Various techniques can be combined and formulated into a uniform package of the strongest measures.

Abstract: The objective of this study is to clarify the deterioration behaviors of overlapping layers between Al-5Mg alloy thermal spray coating and heavy-duty paint coating. Combined cyclic corrosion tests were carried out on common carbon steel plates with overlapping layers. To evaluate the effective area of the sacrificial anode reaction caused by the thermal spray coating, machined straight-line defects with widths of 0.2, 6 and 12 mm were introduced in the overlapping layer. The experimental results indicated that the layers began to deteriorate from the lower part of the thermal spray coating along the defects. The deterioration of the thermal spray coating was accelerated by the sealing treatment. The blister area and height at the overlapping layer were significantly different depending on the sealing treatment.

Abstract: Within the scope of assessment of deteriorating R/C structures, the paper proposes analytical models for the strength of corroded reinforced concrete beams: bending, shear, and bond are considered. Strut and tie models are adapted to include the corrosion effects on geometry, material properties and the load-resisting mechanism; uniform corrosion and pitting are considered. The Model Code 2010 provisions for bond and its deterioration due to low and medium corrosion levels are used for the verification of the models against experimental data of simply supported beams under 3 or 4-point flexure, showing different modes of failure. The innovative contributions are the consideration of bond deterioration effects in the models, with different shear span-to-depth ratios, and the comparison with tests from different campaigns in the literature, using either natural corrosion, environmental corrosion under load or slow artificial corrosion.

Abstract: Based on the results of previous research it could be stated that the deterioration of concrete elements by leaching process could be described by the simplified diffusion function. However the results of Schneider and Chen showed that the deterioration of concrete elements by leaching could differ significantly if they are subjected to permanent bending performance. Their experimental data pointed out that after a certain time the deterioration course of loaded concrete elements significantly changes and these elements lose their strength faster than the unloaded control specimens.Article outlines the possible theoretical solution of this phenomenon. The developed theoretical models where applied to the experimental results of Schneider and Chen [3], [2]. The main task was to find a simplified engineering solution to the problem of the stress corrosion of the concrete in ammonium nitrate solution.

Abstract: Advanced methods of reliability analysis based on simulation techniques of Monte Carlo type in combination with nonlinear finite element method analysis represent effective tools for reliability assessment of the existing bridges. Knowledge of current level of load bearing capacity of the bridge and its development in the coming years while meeting the required level of reliability may help to schedule the bridge maintenance systematically and efficiently and/or it can facilitate decision-making on the manner and extent of its reconstruction. The paper briefly introduces methodology of probabilistic determination of the load bearing capacity of bridges with respect to the ongoing deterioration processes in time. The methodology is applied to determine the current level of load bearing capacity of a reinforced concrete parapet beam bridge built and for its estimation in the coming years until the end of the theoretical service life of the structure.