The main issue of the article is the corrosion of the reinforced concrete elements by the co-influence of the aggressive and power factors. The problem of corrosion is extremely actual one. Therefore the tests were carried out upon the specimens considering the corrosion in the acid environment, namely 10 % H2SO4. The acid environment H2SO4 was taken as a model of the aggressive environment. Conclusions concerning the corrosion model of the cross section and investigation of stress-strain state have been made. That material concerns the problem of the reinforced concrete corrosion as a whole construction. Reinforced concrete beams were tested with and without the co-action of the aggressive environment and power factor.
Determination of shear-load-bearing capacity of reinforced concrete beams (according to the current normative documents), comprises particular recommended values, which do not depend on the parameters of the sample or load. This article de-scribes the methodology for determination the shear strength with suggestions for calculation the coefficient CRd,c and compressed element tilt angle Ѳ while reinforced concrete elements` calculation with the use of “truss model”. In order to confirm the methodology 4 reinforced concrete beams were tested. Tests were performed in order to investigate each particular inclined section separately. Variable parameter was the relative shear span a/d, with its values a/d=2, a/d=1,5 and a/d=1. Another parameter was the usage of composite strengthening system, made for relative shear span a\d=2. Samples were tested as single-span beams subjected to short-term loading. The calculation with the use only the values, given in norms showed significant divergence of results. Using the refined parameter values provided the convergence of results within 16-29% toward overestimation of the experimental data. The composite reinforcement system calculation showed the overestimation of 23%, which is within the same limits as for the control samples.
The stress-strain state of reinforced concrete elements is rather complicated issue of scientific research, which integrates different factors, such as the load type, atmospheric conditions, various defects, damages, geometric deviations. It is commonly known that corrosion of reinforced concrete elements affects both the strength and deformation parameters of the structure significantly; thus, internal stresses` parameters are also influenced. Therefore, detailed theoretical investigation of this issue is the main goal of this article. The detailed literature review and thorough analysis was conducted concerning previous experimental and theoretical studies of the corrosion defects` influence on the reinforced concrete elements` stress-strain state. Existing data and results were systematized and analyzed. On the basis of provided research it could be concluded that the reinforced concrete elements` stressstrain state greatly depends on existing damages and impurities. The stress-strain state could be complicated on micro-scale due to material chemical and mechanical peculiarities; simultaneously on macro-scale the bearing capacity is of the structure could be reduced in general. In the articles existing methods for this issue simulation and evaluation are described and perspective fields for further research are identified. The practical significance of the article is due to complex approach to the research and multilateral identification of the main issue key points.
In this article presented results of researching corrosion of steel bars in aggressive environment in time under loading. For researching were used special equipment. The experience and research works shown that steel bars in the crack cross-section area can be corrode. With increasing width of crack in re-bars and power of aggressive of environment increased the level of corrosion and decreased time of progress. The level of danger of corrosion in the crack in depend of specialty of steel bars. It is geometry parameters of steel bars and characteristic of corrosive behaviour. The general tendency of the influence of various defects on the strength of steels is widely studied experimentally and theoretically only for geometrically correct stress concentrators. For damages that are irregular in shape, such as corrosion ulcers, significantly less researching in each case must experiment to find their effect on the mechanical properties of steels. In this work the influence of simultaneous action of the aggressive environment and loading on strength of steel rebars has been described.
This article presented results of impact corrosion on reinforce concrete beams during time with previous loading. Before testing the RC beams were loaded by 37% and 75% from bearing-capacity load of undamaged corrosion beams. There were tested two types of beams. First type beams were tested under force loading action and second type beams were tested under force loading and corrosion action. As an aggressive environment were used the 10% solution of sulfuric acid H2SO4. Such environment takes place in separate chemical manufactures, galvanic workshops, flue pipes of thermal power plants. The results of experimental studies have established that the effect of the aggressive environment with simultaneous loading significantly impairs the stress-strain state of reinforced concrete beams. Bearing capacity due to the yielding of reinforcement bars for specimens with the simultaneous action of aggressive environment and previous loading of 37% and 75% takes place on 51…53 and 58…60 days. The destruction of these specimens, by crushing compressive concrete, at previous loading 37% occurred after 75…79 and at previous loading 75% - after 79…88 days. The history loading does not impact significantly on beams failure, on finite deflections and timing exhaustion bearing capacity since the start of the simultaneous action of aggressive environment and loading.
In current economic trends, changes in construction using are required. It usually leads to changes in value and type of the working load on building structures, with the requirement to rate the technical state and replace or strengthen the elements. An important aspect of determining the residual bearing capacity of damaged bending reinforced concrete elements is the research concerning the influence of difference defects and damages on the change of strength and deformability. In the article main types of damages and defects, methods of studies of damaged reinforced concrete elements and the expediency of usage of this elements are described. However, most methods are suitable only for certain defects and damages due to the large complexity of calculations and the consideration of multifactoriality. Significant complexity of a single method for calculating damaged elements depends on the possible changing stress strain state of an element in combination with certain defects and damages, the presence of a non-complete separation where during loading or alteration of the damaged element the fractions become included in the work, reinforced concrete is the composite material which carrying complexity in calculating the joint work of its components.
In this article, the results of glue material regarding concrete connections between existent and new concrete bonds are presented. The basic experimental studies into selecting the optimal bonding layer involved testing 100 × 100 × 100 mm concrete cubes. These cubes modeled so-called “old” concrete constructions. Because most of the currently used reinforced concrete structures that require reinforcement or restoration were made decades ago, most of them do not contain chemical additives and multi-fractional concrete, so the concrete composition was adopted in the proper way, namely ordinary heavy concrete in 1970-1980. As a result of the experimental testing of concrete specimen restoration by means of a clamp arrangement, it is established that the maximum compatible work of “old” and “new” concretes is ensured by the use of bonding layers of specially modified mineral materials and the use of concretes using superplasticizers and a selection of their fractional composition.
Przedstawiono wyniki badań dotyczące połączeń kleju betonowego między istniejącym a nowym spoiwem betonowym. Podstawowe badania eksperymentalne mające na celu wybranie optymalnej warstwy wiążącej obejmowały testowanie kostek betonowych 100 × 100 × 100 mm. Na kostkach tych zamodelowana została tak zwana „stara” konstrukcja betonowa. Ponieważ większość obecnie stosowanych konstrukcji żelbetowych, które wymagają zbrojenia lub renowacji, została wykonana kilkadziesiąt lat temu, większość z nich nie zawierała dodatków chemicznych i wielofrakcyjnego betonu, a więc skład betonu został przyjęty w odpowiedni sposób, a mianowicie jako zwykły ciężki beton z lat 1970-1980. W wyniku przeprowadzonych badań odtworzonych próbek betonu za pomocą układu zaciskowego ustalono, że maksymalne kompatybilne działanie „starych” i „nowych” betonów jest zapewnione przez zastosowanie warstw wiążących ze specjalnych modyfikowanych materiałów mineralnych oraz wykorzystanie betonów z superplastyfikatorami i dobór ich odpowiedniego składu frakcyjnego.