The current state of knowledge on concrete carbonation has proven that this phenomenon is one of the key factors influencing the reinforced concrete durability reduction during the operational ...period. To date, the carbonation process has been researched quite deeply; however, the dependence of its course on a variety of external and internal factors poses a significant problem in service life predictions for concrete constructions. The development of nuclear infrastructure around the world in recent years has set scientists the task of investigating such processes in conditions different from those usual for industrial and civil construction. In particular, information in open sources on the course of the carbonation process under irradiation conditions is insufficient. The manuscript analyzes the existing data on concrete carbonation, including a review of the main methods for studying the carbonation process, key factors influencing the course of this process, applied methods of mathematical analysis, predictive models of service life, dynamics of carbonation development, and the application of such analytical models in practice. The available information about the carbonation process under various types of irradiations on the causes, dynamics, and mechanisms of carbonation and corrosion processes occurring in reinforced concrete during operation is also considered. Based on the results of the analysis carried out in the study, recommendations are given for further development in the research field of carbonation process in concrete structures of nuclear power plants in order to comprehensively predict their service life.
To ensure the safe operation of concrete structures of deep-burial storages, it is necessary to research the degradation mechanisms of such structures. Concrete carbonation is one of the key factors ...determining the service life of concrete structures. Existing methods for the concrete carbonation process research at various stages of the building structure life cycle make it possible to conduct model tests in the shortest possible time by simulating the operational factors influencing the corrosion process development. The authors carried out model tests of concrete of deep-burial storages using the method of accelerated concrete carbonation and by taking into account the effects of elevated temperatures. When exposed to elevated temperatures during carbonation, concrete samples exhibit a decrease in compressive strength in the first 56 days of testing by an average of 1.6 MPa. However, by the end of the tests (168 days), the strength of concrete samples at elevated temperatures is on average 4 MPa higher. The microstructure and carbonation dynamics were studied by XRD, TGA and SEM. The data obtained in the research can be used to develop models for predicting the service life of concrete structures of deep-burial storages.
This paper presents the results of experimental studies of load characteristic changes during the upsetting of high billets with the upsetting ratio (height to diameter ratio) from 3.0 to 6.0, which ...is followed by buckling. Such pass is an effective way of preforming the workpiece for production of forgings with a bended axis or dual forming, and belongs to impression-free (dieless) operation of bulk forming. Based on the experimental data analysis, an engineering method for calculation of workpiece pre-forming load as a maximum buckling force has been developed. The analysis of the obtained data confirmed the possibility of performing of this pre-forming operation on the main forging equipment, since the load of shaping by buckling does not exceed the load of the dieforging.
This paper analyses the stresses in continuous welded rails on bridges including the aspect of fatigue of rail steel. Furthermore, it examines the possibility to avoid rail expansion joints, while ...simultaneously exploiting the permissible stress capacity of the rail profile 60E1. Accordingly, general application of permissible values of pressure and tensilestresses prescribed in the current European standards was critically analysed. Paper includes specific application aspects of the prescribed stress values for railway bridges in Serbia. General algorithm for reducing the stresses due to the vehicle/track/bridge interaction, which is presented in this paper, was developed by the authors. This algorithm includes all essential parameters of the bridge structure and railway superstructure, as well as the influence of climate conditions and railway route design.
This work represents the stage of the author's research aimed at identifying the solutions for increasing the energy efficiency of the production of precast concrete and reinforced concrete products ...and structures in plant conditions due to reducing the temperature of heat treatment, or due to the reduction of duration of this technological process. The work provides results of the research of the influence of the admixture of lithium carbonate (Li
2
CO
3
) on the dynamics of hydration process of the binding systems on a cement basis in the conditions of the increased temperature (40°C). The research was performed using the method of isothermal calorimetry on the two various samples of the cement binder, conducted in various countries. The Li
2
CO
3
admixture is accepted in dosages from 0.5% to 2.5%. The graphical dependence of the heat flow of the exothermic reaction of hydration on the used lithium carbonate dosage in the first days of curing of the samples is established and presented.
The assessments were made in the current practice based on the design foundation of high-rise buildings in Moscow to find a method for improving the soil foundation. Many references showed that the ...current design was controlled by structural engineers. They commonly used the old methods of analysis, the first part was carried out for the design of the structure and architecture of high-rise building, the second part of the study was to explore the benefit of adopting the application of stone columns raft foundation design concept. A comparative study was made between the results of the 3-dimensional finite element (3D FEM) analysis in SCAD software. The results showed that the plate foundation of the building does not satisfy to carry the total load without some meaning of improvement. The 3D FEM by PLAXIS 3D showed that the used stone columns decreased the settlement because about 70-80% of the total building loads were carried by columns when the raft was placed in the stiff clay layer. The number of columns in the raft foundation can be significantly reduced, particularly if the soil had strong characteristics. The raft foundation settlement can be significantly reduced, particularly if the soil had strong characteristics.
These studies are aimed at improving the performance of gypsum materials and products by using in their composition waste production of basalt fibers. The purpose of this study is to prove the ...possibility of using waste production of basalt fibers as a filler in gypsum composites. As the main materials used gypsum binder (Samara), as well as waste production of basalt fibers (Tver production). The positive effect of the waste is due to the participation of soluble minerals of basalt in the processes of hardening of gypsum binder. Also, the waste particles form a more perfect structure of gypsum stone., filling the pore space. It is revealed that the use of waste production of basalt fibers is advisable to use as a filler in gypsum composites.
The road-maintenance strategies vary from one country to another, and even between the road management authorities within a one single country. It is not surprising, as there is not best maintenance ...method, nor a universal set of strategies that can be applied equally everywhere. Generally, there are strategies acceptable in certain conditions, but the factors influencing the selection process are diverse and very complex. This paper will present a review of the various measures that can be applied on the roads, which is certainly the basic condition of selection of an appropriate maintenance strategy.
Worldwide practice recommends validation of the HDM models with some other software that can be used for comparison of the forecasting results. The program package MATLAB is used in this case, as it ...enables for modelling of all the HDM models. A statistic validation of the results of the forecasts concerning the condition of the pavements in HDM with the on-field measuring results was also performed. This paper shall present the results of the validation of the coefficients of calibration of the deterioration models in HDM 4 on the Macedonian highways.
Waste disposal in the production of building materials and the organization of waste-free technological processes require a large amount of multilateral research. The application of basalt dust in ...the production of gypsum materials has been little studied. The paper investigated the effect of basalt dust - waste production of basalt fibers, on the working mixtures and the properties of hemihydrate of calcium sulfate paste (standard consistency, setting time of gypsum dough, water absorption of the resulting gypsum stone). It is known that the addition of basalt waste has a positive effect on strength, but there is no data on its effect on the rheological properties of gypsum mixtures. It was revealed that the introduction of basalt dust into the composition of the gypsum composite contributes to the change of the plaster mix rheology and of the properties of the gypsum structure. This must be taken into account when selecting optimized formulations of working mixtures on the hemihydrate of calcium sulfate.
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