Degradation of Materials Based on Alkali-Activated Blast-Furnace Slag after Exposure to Aggressive Environments

The paper summarizes partial results of a study of degradation of materials based on alkali-activated blast-furnace slag (AAS) and comparative on cement CEM III/A 32.5 R after exposure to aggressive environments. It further specifies the possibilities for utilising destructive and non-destructive techniques to determine the progress of degradation and characterizes the degree of their correlation. After 28 days of ageing in a water environment, the produced test specimens (40×40×160 mm beams) were placed in aggressive media (ammonium nitrate solutions; sodium sulfate, rotating water) and after subsequent 28, 56 and 84 days of degradation were subjected to testing. Testing comprised both a destructive form (determination of compressive strength and flexural strength) and a selected non-destructive technique (Impact-echo method). The partial outputs were supplemented by the results acquired from monitoring weight changes. In addition, the development of Ultrasonic Pulse Velocity in relation to the progress of the degradation processes was also monitored. While the exposure of both test specimens to water and sodium sulfate did not result in any significant changes, the exposure to the ammonium nitrate solution exhibited rapid signs of degradation associated with a significant reduction in functional characteristics.

The Impact of Bacteria of the Genus Bacillus upon the Biodamage/Biodegradation of Some Metals and Extensively Used Petroleum-Based Plastics

This paper tackles bacteria of the genus Bacillus as both biodamaging/biodegrading and biocontrolling agents. The article addresses the said bacteria’s ability to form biofilms and corrosive, antimicrobial and antibiofilm proactive compounds, primarily, siderophores. Their role depends on the species, microorganism strain, production of antimicrobial substances, biofilm formation, and the type of damaged material. The bacteria under analysis have demonstrated the ability to cause as well as inhibit biodamage. The involvement of bacteria of the genus Bacillus in microbiologically influenced corrosion processes is determined by the production of corrosive metabolites and the impact of certain bioelectrochemical mechanisms. Lipopeptides generated by Bacillus subtilis (surfactin, iturin and fengycin) are capable of modifying surfaces’ hydrophobic properties and impacting the microbes’ adhesion to surfaces. Produced by Bacillus velezensis, the siderophore bacillibactin at a high concentration is capable of inhibiting the formation of bacterial biofilms, thus slowing down the degradation of materials. Further study of siderophores as green inhibitors of microbiologically influenced corrosion may be promising as the said compounds possess antibiofilm-forming properties and high-intensity inhibitory capabilities.

Koji Molds for Japanese Soy Sauce Brewing: Characteristics and Key Enzymes

Soy sauce is a traditional Japanese condiment produced from the fermentation of soybeans, wheat, and salt by three types of microorganisms, namely koji molds, halophilic lactic acid bacteria, and salt-tolerant yeast. The delicate balance between taste, aroma, and color contributes to the characteristic delicious flavor imparted by soy sauce. In soy sauce brewing, protein and starch of the raw materials are hydrolyzed into amino acids and sugars by enzymes derived from koji molds. These enzymatically hydrolyzed products not only directly contribute to the taste but are further metabolized by lactic acid bacteria and yeasts to most of organic acids and aromatic compounds, resulting in its distinctive flavor and aroma. The color of the soy sauce is also due to the chemical reactions between amino acids and sugars during fermentation. Therefore, koji mold, which produces various enzymes for the breakdown of raw materials, is an essential microorganism in soy sauce production and plays an essential role in fermenting the ingredients. In this review, we describe the manufacturing process of Japanese soy sauce, the characteristics of koji molds that are suitable for soy sauce brewing, and the key enzymes produced by koji molds and their roles in the degradation of materials during soy sauce fermentation, focusing on the production of umami taste in soy sauce brewing.

DETECTION OF STRUCTURAL PATHOLOGIES IN BUILDINGS USING ARCHITECTURAL PHOTOGRAMMETRY

Environmental pollution and natural degradation of materials cause deterioration in buildings, initiating pathological processes that require conservation actions. Architectural Photogrammetry will be discussed as a tool to identify different pathologies on buildings and to accurately measure deflections. A photographic study was conducted of the most common deflections on reinforced concrete structures, with samples of different ages and locations exposed to various environments within Holguin Province in Cuba to detect deterioration characteristics, causes and possible treatments. A comparative analysis of other common methods and instruments currently used to measure structural pathologies highlights the efficiency of architectural photogrammetry. Photogrammetry is suitable to study the most common pathologies, their causes, and potential solutions. These include: cracks, fissures, deflection in beams, footing settlement, slenderness in columns, and more. In addition to the scope and efficiency of photogrammetry, this technology also facilitates studying inaccessible points on large elements. The instantaneous recording of accurate data about physical objects gives photogrammetry advantages over conventional structural analysis methods.

Design, fabrication, testing and operation of a simulation facility for high temperature molten salt studies

Purpose Concentrated solar power and molten salt reactors use molten salts for heat energy storage and transfer. FLiNaK salts are being proposed to be used in these plants. However, structural material compatibility is the main hurdle for using molten salt in these systems. Hence, it is essential to study the degradation of materials in high temperature molten FLiNaK salt environment. In view of this paper aims to describe, a simulation facility which was established and operated for carrying out high temperature static corrosion studies of materials under molten FLiNaK salt. Design/methodology/approach This paper describes about the design criteria, method of designing using ASME codes, material selection, fabrication, testing, commissioning and operation. Also, a few experimental results have been illustrated. Findings A simulation facility could be designed, fabricated, commissioned and is being successfully operated to carry out corrosion experiments under static molten FLiNaK environment. Research limitations/implications The facility has been designed for 800°C and maximum temperature of experiment would be restricted to 750°C. The materials tested in this facility can be validated only up to 750°C temperature. A maximum of four exposure periods can be studied at a time with around ten specimens for each exposure. Originality/value Selection of compatible material for the facility and design certain unique features like extracting exposed specimens of intermediate periods without actually shutting down the autoclave and measuring the level of molten salt at high temperature.

Strategies for High-Temperature Corrosion Simulations of Fe-Based Alloys Using the Calphad Approach: Part I

The environmental degradation of materials at high temperatures limits the useful life of different industrial components and hinders the development of more economical and environmentally friendly processes for the energy production. Despite the importance of this phenomena, a model to predict lifetime of materials that degrade due to high-temperature corrosion has up till now been lacking due to limitations of the computational possibilities and the complex nature of oxidation. In the present work we develop some strategies to model high-temperature corrosion in Fe-based alloys using the Calphad (Calculation of Phase Diagrams) approach. It is proposed that kinetic-based simulations for oxidation of Al and Cr can accurately represent the lifetime of the protective layers in FeCrAl and FeCr alloys at different temperatures in air. The oxide systems are in addition investigated by equilibrium calculations. The corrosion mechanisms of FeCr and FeCrAl alloys are discussed based on theoretical and experimental knowledge.

Chemical Degradation of the La0.6Sr0.4Co0.2Fe0.8O3−δ/Ce0.8Sm0.2O2−δ Interface during Sintering and Cell Operation

A complete cell consisting of NiO-Ce0.8Sm0.2O3−δ//Ce0.8Sm0.2O3−δ//(La0.6Sr0.4)0.95Co0.2Fe0.8O3−δ elaborated by a co-tape casting and co-sintering process and tested in operating fuel cell conditions exhibited a strong degradation in performance over time. Study of the cathode–electrolyte interface after cell testing showed, on one hand, the diffusion of lanthanum from (La0.6Sr0.4)0.95Co0.2Fe0.8O3−δ into Sm-doped ceria leading to a La- and Sm-doped ceria phase. On the other hand, Ce and Sm diffused into the perovskite phase of the cathode. The grain boundaries appear to be the preferred pathways of the cation diffusion. Furthermore, a strontium enrichment was clearly observed both in the (La0.6Sr0.4)0.95Co0.2Fe0.8O3−δ layer and at the interface with electrolyte. X-ray photoelectron spectroscopy (XPS) indicates that this Sr-rich phase corresponded to SrCO3. These different phenomena led to a chemical degradation of materials and interfaces, explaining the decrease in electrochemical performance.

Self-Excited Acoustical System Frequency Monitoring for Refractory Concrete under Uniaxial Compression

The characterization of materials, stress and fatigue state monitoring based on the acoustoelastic principle are gaining widespread attention in recent years, mainly due to their advantages such as high sensitivity and non-destructive character. This article presents the application of a non-destructive acoustic method to test the degree of degradation of materials with which the heating boiler is coated. The combustion chamber is covered in materials when the temperature of the process itself increases, and has a very positive effect on fuel combustion. Unfortunately, with the passage of time, such materials undergo gradation. This article describes an innovative measuring system that has been successfully applied to monitor changes in resonance frequency under uniaxial compression in refractory grade material, which by definition is characterized by a high level of heterogeneity with a network of pre-existing cracks. The paper indicates that both stress and elasticity coefficients have an impact on the vibration frequency of the measuring system. Initial research was conducted to qualitatively determine the influence of these parameters on the measured frequency of the system.

Finite Element Modeling of Bond Behavior of FRP and Steel Plates

Strengthening systems for existing reinforced concrete (RC) structures are increasingly needed due to several problems such as degradation of materials over the time, underdesign, serviceability or seismic upgrading, or new code requirements. In the last decades, strengthening by fibers composite materials applied with various techniques (FRP, FRCM, NSM) were largely investigated and theoretical formulations have been introduced in national and international design guidelines. Although they are an excellent strengthening solution, steel plates may represent still a valid traditional alternative, due to low costs, ductile stress-strain behavior, simple and fast mounting with possibility of reusing the material. Guidelines for a correct design are still lack and, therefore, detailed models and design formulas are needed. In this paper, the bond behavior at the plate-concrete interface, which plays a key role for the effectiveness of the strengthening system, is analyzed by means of 3D finite element models calibrated on experimental results available in literature. Parametric analyses were carried out by changing some meaningful parameters.

Tribological Study of the Friction between the Same Two Materials (RAD Steel)

These demands more and more severe of the organs of friction lead to operating temperatures of more and more high which result in particular a degradation of materials. This is reflected by decreases of performance that could jeopardize the safety (fall of the coefficient of friction) and penalize the economic balance (increase the wear). Our study highlights the interactions between the thermal, tribology, and physicochemistry and has been designed to respond to the following three objectives: (1) characterize at the macrolevel the phenomena of thermal localization and identify their influence on the coefficient of friction, (2) correlate to the local scale these phenomena to the physical mechanisms of friction, and (3) to identify the consequences of the degradation of the material with the temperature, based on the coefficient of friction and the physical mechanisms of friction.