A Review Predictive Mathematical Modeling of Alkali-Silica Reaction in Concrete: evolution, current understanding and the knowledge gaps

Predictive mathematical models have been proposed in alkali-silica reaction (ASR). Predicting concrete degradation and its effects on mechanical properties is of interest given the long time until degradation becomes critical for intervention and recovery, and difficult structural access for predictive and corrective monitoring and treatment. The present paper presents a general overview of the evolution of the aforementioned predictive mathematical models, interrelating them to the maturation of the phenomenological state of the art associated with ASR. For this purpose, a systematic literature review was used, followed by bibliometric analysis and meta-analysis. In this study, 104 articles from 1974 to 2020 were selected, of which 31 articles were reviewed on the topic of mathematical modeling of ASR. The results of the method indicated the importance of the methodological approach of literature review to provide a comprehensive and chronological view of the evolution of ASR consolidated in the literature. It was found that the mathematical models have evolved considering the phenomenological approach of ASR.

An experimental approach to the influence of partial rebar corrosion and concrete degradation on behavior of FRP-strengthened RC beams

Human factors are one of the main reasons for structural damage as they decrease the bearing capacity and also lead to an inaccurate estimation of the structure. Previous studies show that the use of CFRP in the damaged structures can significantly increase their bending and shear capacity. This study examines the capacity and cracks distribution in eight RC (reinforced concrete) beams (210 × 250 × 250 cm), each of which was rehabilitated with seven CFRP (carbon fiber-reinforced polymer) strips using the strip method. Each beam, except for the control specimen, experiences different types of concrete and rebar damages, which are finally compared with those of the control specimen. The results indicated that rebar damage in all the beams was significant and the effects of concrete damage were minimized by CFRP strips. Moreover, the force–displacement diagrams indicate the greatest force for the control specimen. Other specimens reached up to 80% of the force experienced by the control specimen. Finally, the parametric study showed that the influence of the crack width on decreasing the bearing capacity was more significant compared with the other parameters.

Hydrogen Sulphide in Industrial Enterprises Water Management Infrastructure - The Factor of Chemical and Microbiological Corrosion Concrete Degradation of Water Facilities

The durability of concrete, the material which is widely used for water facilities depends on accumulation in operational environments (drain water, air-gas space) of hydrogen sulfide. Now the mechanism of corrosion destruction of concrete in drainage pipelines is represented as result of biogenous sulphuric acid aggression – influence of the sulphuric acid formed by thionic bacteria. The analysis of data on H2S concentration in drain waters of various industrial enterprises demonstrates that they create in gaseous operational media H2S concentration, sufficient for development in aerobic conditions of thionic bacteria. As the results of urban sewer networks inspection have shown, the correlation between concentration of H2S in aqueous phase and its concentration in air environment, between concentration of H2S in air environment and the corrosion rate of concrete’s coffering part is observed. Chemical and X-ray crystallography of this concrete showed that in corrosive concrete decreases pH, reaching in some examples of values 1-2, and sulfates collect. In dynamics of corrosion process the exponential growth of concentration in concrete of extremely acidophilic thionic bacteria is noted.

Integration of practical supplemental measurements into bridge condition visual inspection grading

The reliability of condition assessment of bridges obtained from analysis of visual inspection data is always a big concern among structural engineers. It has been known that the condition grading of a bridge is very subjective and can convey limited information to the end user. To finalize and verify the reported condition grading, inspectors and bridge owners have mainly been relying on images. It has been known that the image observation may not be sufficient to address all kinds of problems associated with visual condition grading. The integration of practical supplemental measurements into condition grading as proposed in this paper will contribute to minimize the errors in visual inspection. Measurement of vehicle induced vibrations through wireless accelerometers can be used to determine the natural frequencies of the bridge that can be reported at each inspection. The change in frequencies can be an indication of deterioration in stiffness of bridge over the years. Taking concrete samples by chipping at the inspection site and analyzing them under scanning electron microscope (SEM) at the laboratory can be used to identify the current problems with concrete degradation. In this scope, the regular bridge inspection procedure with the proposed enhancements has been performed on field inspection of highway bridges in Turkey to determine the practicality of the quick supplemental measurements and to analyze the difference in grading of the three different inspectors with different level of experiences.

A Comprehensive Review on the Mechanism of Concrete Deterioration in Accelerated Aggressive Environment

Concrete is being extensively utilized for the constructional and other allied works on account of its versatility and mechanical properties. However, it exists to be in a state of disequilibrium with its ambient environment owing to its universal alkaline nature and hence is susceptible to deterioration when exposed to aggressive environments. The reactive species emanating from chemical plants, fertiliser industries, marine water, agro-food industries etc., produce detrimental effects on the concrete structures through the dissolution of calcium bearing phases from the hydrated matrix. This degradation culminates in decalcification, volumetric expansion, salt crystallisation, micro-cracking, surface scaling, delamination, spalling and corrosion. Diffusivity, capillary porosity, permeability, chemical nature of hydrated matrix and pore network are the parameters that influence the chemical mechanism of concrete degradation. The mechanism of concrete degradation is distinct for various aggressive species and its fair comprehension remains as one of the challenges in accomplishing the durability based concrete design. This paper critically reviews the basic mechanism of the concrete deterioration in accelerated aggressive environment of mineral acids, organic acids and inorganic salts. In addition to this, a glimpse of the effect of degradation on different binder systems viz., Ordinary Portland Cement system, blended cement system, special cement system and alkali activated system is provided.

FACTORS INFLUENCING THE INTENSITY OF WEAR AND TEAR OF CONCRETE AND REINFORCED CONCRETE STRUCTURES OF HYDRAULIC FACILITIES

The peculiarity of special-purpose hydraulic engineering facilities significantly increases the importance of the wrong choice of materials associated with an underestimation of the existing loads, operating conditions and aging (wear) processes as a result of interaction with accumulation and storage of products. The intensity of the degradation process is connected with the action of force factors, physical fields, chemicals, living organisms, etc. Therefore, the most important factor determining the durability of an object is the rate of degradation of its structures. In addition to the analytical and numerical approaches, concrete degradation is also considered from the point of view of the stages of its decomposition. The weakest, from the point of view of corrosion, component of concrete is cement stone which determines the intensity of concrete destruction, depending on the mechanism of interaction with an aggressive environment. The constant impact of an aggressive environment on concrete components determines the development of corrosion processes in its very thickness. In the course of corrosion of the concrete material, various mechanisms for the transfer of aggressive substances appear which indicates that during the degradation of building structures made of concrete or reinforced concrete, a complex set of transformations occurs leading to a change in the properties of concrete in structures.

Cold Ironing Galvanic Corrosion Issues with Regard to a Shore-to-Ship Medium Voltage Connection

Cold ironing refers to the usage of less polluting power supply sources to deliver electricity to the moored ship. Such a shore-to-ship system is used when the ship is at a port so the auxiliary combustion engines may be turned off. This paper presents the numerical simulation results of a medium voltage cold-ironing system with regard to the currents flowing between the ship’s hull and grounding busbar. The IT electrical inland system with a neutral grounding resistor, as commonly used in shore-to-ship systems, is investigated. Parasitic capacitances present between the phase-to-hull and phase-to-ground in real-world applications can vary from each other. The direct and alternating currents flowing across the hull, seawater and the pier structure are amongst the causes that can lead to premature reinforced concrete degradation. Chosen cases of phase-to-ground or hull unequal capacitances influencing AC stray currents were considered.