scholarly journals Analysis of impact of aeration modifications on strength parameters of concrete under fire conditions

2018 ◽  
Vol 188 (2) ◽  
pp. 187-196
Author(s):  
Pawel Ogrodnik ◽  
Bartosz Zegardlo
Keyword(s):  
Building Materials ◽  
Effective Means ◽  
High Strength ◽  
Strength Properties ◽  
Building Industry ◽  
Air Bubbles ◽  
Sudden Increase ◽  
Strength Parameters ◽  
Linear Deformation ◽  
Aerated Concrete

Modern dynamically developing building industry poses more and more complex challenges to building materials. Elevated constructions must satisfy a number of requirements including safety, durability and being environmentally friendly. The unfavorable impact of increased temperatures on the work of a construction structure is manifested by the change in the properties of the heated material and the occurrence of deformation, stresses and thermal scratches. These are particularly dangerous phenomena when they occur in elements with limited freedom of linear deformation. The purpose of the research presented in this article was to find a solution for concrete that is both resistant to spalling and characterized by high strength properties after heating. The main thesis put forward by the authors of the article is the assumption that deliberate concrete aeration will allow the introduction of evenly distributed micro air bubbles into its volume, which will constitute a reservoir for increasing the volume of water converting into water vapor as a result of a sudden increase in temperature. The presented schema enabled the assumption that the strength parameters of aerated concrete would decrease slightly in relation to non-aerated concrete, however it would be still possible to use in reinforced concrete constructions. As can be seen from the aforementioned analyzes, aeration modification can be an effective means of designing high temperature resistant concrete.

scholarly journals Concrete based on sulfur binder being modified with inorganic additives

2018 ◽  
Vol 212 ◽  
pp. 01013
Author(s):  
Vadim Balabanov ◽  
Victor Baryshok ◽  
Nikita Epishkin
Keyword(s):  
Frost Resistance ◽  
Building Materials ◽  
Physical And Mechanical Properties ◽  
High Strength ◽  
Strength Properties ◽  
Climatic Conditions ◽  
Freezing And Thawing ◽  
Concrete Mixtures ◽  
Irkutsk Region ◽  
Water Saturated

The sharply continental climate of the Irkutsk region is characterized by wide temperature intervals throughout the year. The repeated cyclicity of freezing and thawing of building materials in the water-saturated state influences the change in technical characteristics and the durability of concrete products and structures. The concrete products’ features in such climatic conditions create the need for the production of concretes with improved indicators of physical and mechanical properties. The effect of modifying additives on the technological characteristics of sulfur concrete is established. The effect of all elements of sulfur concrete on its strength and frost resistance. The composition of sulfuric concrete is obtained, which meets all the requirements and also has high strength and increased frost resistance. Formulations with a certain ratio of structural sulfuric concrete mixtures were developed. As a result of the use of technical sulfur in the composition of concrete products, the problem of utilizing annually accumulating reserves of technical sulfur is partially solved. The strength properties of sulfuric concretes easily compete with high-quality brands of concrete, special types of concretes that have in their composition additives.

scholarly journals Impact of Elevated Temperatures on Strength Properties and Microstructure of Calcium Sulfoaluminate Paste

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6751
Author(s):  
Konrad A. Sodol ◽  
Łukasz Kaczmarek ◽  
Jacek Szer ◽  
Sebastian Miszczak ◽  
Mariusz Stegliński
Keyword(s):  
Compressive Strength ◽  
Building Materials ◽  
Elevated Temperatures ◽  
Cooling System ◽  
Base Material ◽  
Visual Assessment ◽  
Strength Properties ◽  
Strength Parameters ◽  
Calcium Sulfoaluminate ◽  
Wide Range

This article is motivated by civil fire safety. Fire-prevention engineering demands a wide range of information about building materials including alternative cements, for instance CSA-cement. Because of exposure of the cement-base material to a high temperature, its strength properties deteriorate due to dehydration connected with phase and microstructure changes. Previous research indicated that the main endothermic reaction of CSA-based composite, dehydration of ettringite, might be used as a cooling system for a metal structure during fire-load. This article examines visual assessment, microstructure, density, as well as flexural and compressive strength parameters of CSA-based composite after isothermal heating at temperatures from 23 °C to 800 °C. The results of SEM/EDS investigations showed that the calcium sulfoaluminate paste may start partially re-sintering above 600 °C. Mechanical tests revealed significant reduction of strength parameters but residual compressive strength was maintained in the whole temperature range e.g., 8 MPa at 800 °C. Additionally, visual assessment of the specimens indicated that it might be possible to predict the material temperature heating based on the specific surface color. These findings add to the evidence of general knowledge about CSA hydrates.

scholarly journals Improving energy efficiency through the use of waste heat products in the production of building materials

2021 ◽  
Vol 311 ◽  
pp. 07007
Author(s):  
Galina Medvedeva ◽  
Kamilla Giniyatova ◽  
Kamilia Minikaeva
Keyword(s):  
Sustainable Management ◽  
Building Materials ◽  
Waste Heat ◽  
Coal Ash ◽  
High Strength ◽  
Strength Properties ◽  
Waste Products ◽  
Insulating Material ◽  
Fine Grained ◽  
Cellular Concrete

Concern for the sustainable management and recycling of solid waste is becoming more visible in all sectors of the economy. This study explores the possibility of using coal ash residue (waste from Kazan CHPP-2) as a substitute for fine-grained aggregate in sulfur concrete. The trend towards an increase in the level of utilization of waste heat power engineering is an important task. The chemical composition, microstructure and mechanical properties, including density, water absorption, compressive strength and thermal conductivity of sulfur concrete, including coal ash with partial and complete sand replacement, were investigated and the results were compared with those for standard cellular concrete. The authors studied modern heat-insulating materials and materials from industrial waste products. The article analyzes the estimated thickness of the insulating material depending on the type of structure. Outside walls made of sulfur concrete, in addition to high strength properties, have high thermal and economic performance.

A novel predictive method for filler coflocculation with cellulose microfibrils

TAPPI Journal ◽  
2019 ◽  
Vol 18 (11) ◽  
pp. 653-664
Author(s):  
IGNACIO DE SAN PIO ◽  
KLAS G. JOHANSSON ◽  
PAUL KROCHAK
Keyword(s):  
Negative Impact ◽  
High Strength ◽  
Strength Properties ◽  
Cellulose Microfibrils ◽  
Paper Strength ◽  
Flow Loop ◽  
Cationic Starch ◽  
Reflectance Measurement ◽  
Drainage Rate ◽  
Complete Study

Different strategies aimed at reducing the negative impact of fillers on paper strength have been the objective of many studies during the past few decades. Some new strategies have even been patented or commercialized, yet a complete study on the behavior of the filler flocs and their effect on retention, drainage, and formation has not been found in literature. This type of research on fillers is often limited by difficulties in simulating high levels of shear at laboratory scale similar to those at mill scale. To address this challenge, a combination of techniques was used to compare preflocculation (i.e., filler is flocculated before addition to the pulp) with coflocculation strategies (i.e., filler is mixed with a binder and flocculated before addition to the pulp). The effect on filler and fiber flocs size was studied in a pilot flow loop using focal beam reflectance measurement (FBRM) and image analysis. Flocs obtained with cationic polyacrylamide (CPAM) and bentonite were shown to have similar shear resistance with both strategies, whereas cationic starch (CS) was clearly more advantageous when coflocculation strategy was used. The effect of flocculation strategy on drainage rate, STFI formation, ash retention, and standard strength properties was measured. Coflocculation of filler with CPAM plus bentonite or CS showed promising results and produced sheets with high strength but had a negative impact on wire dewatering, opening a door for further optimization.

Causes of gear pump fails and methods for their elimination

2020 ◽  
pp. 98-107
Author(s):  
Vitaliy A. Zuyevskiy ◽  
Daniil O. Klimyuk ◽  
Ivan A. Shemberev
Keyword(s):  
Adhesion Strength ◽  
Production Systems ◽  
Low Cost ◽  
High Strength ◽  
Strength Properties ◽  
Research Purpose ◽  
Working Fluid ◽  
Gear Pump ◽  
Repair Service ◽  
Recovery Method

Gear pumps are an important element of many production systems and their replacement in case of failure can be quite expensive, so it is important to have a modern and well-tuned technology for their recovery. There are many methods for restoring the pump's performance, depending on the reason that led to its failure. (Research purpose) The research purpose is in determining what causes most often lead to loss of pump performance, and developing a recovery method that provides the greatest post-repair service life of the pump and low cost of repair. (Materials and methods) Authors took into account that the applied coatings must have sufficient adhesion strength and resistance to mechanical, thermal and corrosion loads during operation. It was found that most often significant leaks of the working fluid, leading to failure, occur due to an increase in the gap between the inner surface of the housing and the gears due to active wear of the housing wells. Authors determined that the method of electric spark treatment of worn-out housing wells is best suited to perform the task (a large post-repair resource and low costs). (Results and discussion) It was found by laboratory studies of the adhesion strength of electric spark coatings with various electrodes that the best transfer of the material to the substrate is provided by bronze electrodes BrMKts3-1. It was noted that the coatings applied using the BrMKts3-1 electrode have high strength properties. (Conclusions) Research conducted in the center for collective use "Nano-Center" VIM confirmed the possibility of effective recovery of the gear pump by electric spark treatment.

scholarly journals Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1988
Author(s):  
Tibor Kvackaj ◽  
Jana Bidulská ◽  
Róbert Bidulský
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
High Strength Steel ◽  
Single Phase ◽  
Hsla Steel ◽  
High Strength ◽  
Strength Properties ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Steel Grades

This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) depending on differences in their final microstructural components, chemical composition, alloying elements and strengthening contributions to determine strength and mechanical properties. HSS is characterized by a final single-phase structure with reduced perlite content, while AHSS has a final structure of two-phase to multiphase. UHSS is characterized by a single-phase or multiphase structure. The yield strength of the steels have the following value intervals: HSS, 180–550 MPa; AHSS, 260–900 MPa; UHSS, 600–960 MPa. In addition to strength properties, the ductility of these steel grades is also an important parameter. AHSS steel has the best ductility, followed by HSS and UHSS. Within the HSS steel group, high-strength low-alloy (HSLA) steel represents a special subgroup characterized by the use of microalloying elements for special strength and plastic properties. An important parameter determining the strength properties of these steels is the grain-size diameter of the final structure, which depends on the processing conditions of the previous austenitic structure. The influence of reheating temperatures (TReh) and the holding time at the reheating temperature (tReh) of C–Mn–Nb–V HSLA steel was investigated in detail. Mathematical equations describing changes in the diameter of austenite grain size (dγ), depending on reheating temperature and holding time, were derived by the authors. The coordinates of the point where normal grain growth turned abnormal was determined. These coordinates for testing steel are the reheating conditions TReh = 1060 °C, tReh = 1800 s at the diameter of austenite grain size dγ = 100 μm.

scholarly journals Soil microbiomes mediate degradation of vinyl ester-based polymer composites

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Adam M. Breister ◽  
Muhammad A. Imam ◽  
Zhichao Zhou ◽  
Md Ariful Ahsan ◽  
Juan C. Noveron ◽  
...  
Keyword(s):  
Polymer Composites ◽  
Polymer Composite ◽  
Structural Integrity ◽  
Abiotic Factors ◽  
High Strength ◽  
Strength Properties ◽  
Naturally Occurring ◽  
Structural Applications ◽  
Acrylate Esters ◽  
Bacterial Groups

AbstractPolymer composites are attractive for structural applications in the built environment due to their lightweight and high strength properties but suffer from degradation due to environmental factors. While abiotic factors like temperature, moisture, and ultraviolet light are well studied, little is known about the impacts of naturally occurring microbial communities on their structural integrity. Here we apply complementary time-series multi-omics of biofilms growing on polymer composites and materials characterization to elucidate the processes driving their degradation. We measured a reduction in mechanical properties due to biologically driven molecular chain breakage of esters and reconstructed 121 microbial genomes to describe microbial diversity and pathways associated with polymer composite degradation. The polymer composite microbiome is dominated by four bacterial groups including the Candidate Phyla Radiation that possess pathways for breakdown of acrylate, esters, and bisphenol, abundant in composites. We provide a foundation for understanding interactions of next-generation structural materials with their natural environment that can predict their durability and drive future designs.

Correlation Between Microstructure and Mechanical Properties of Diffusion Brazed MAR-M 247

1993 ◽  
Author(s):  
W. Miglietti
Keyword(s):  
Filler Metal ◽  
Turbine Blades ◽  
High Strength ◽  
Strength Properties ◽  
Joint Microstructure ◽  
Investment Cast ◽  
Diffusion Brazing ◽  
Brazed Joints ◽  
Joining Process ◽  
Turbine Blading

Diffusion brazing is a joining process utilized in the manufacture and repair of turbine blades and vanes. MAR-M247 is an investment cast Ni-based superalloy used for turbine blading and has good strength properties at high temperatures. The objectives of this work was to develop a diffusion brazing procedure to achieve high strength joints. A commercially available diffusion brazing filler metal of composition Ni-15Cr-3,5B of 100 μm thickness was used. With the desire to eliminate brittle centre-line phases, the effects of the processing variables (only temperature and time) on the joint microstructure was studied. Once the metallurgy of the joint was understood, mechanical property assessments were undertaken i.e. tensile and creep rupture tests, and the latter being the severest test to evaluate joint strength. The results demonstrated that the diffusion brazed joints had nearly equivalent mechanical strength to that of the parent metal. This showed that the resultant diffusion brazing parameters enabled effective and reliable joining of MAR-M247.

scholarly journals Analysis of Porous Structure in Autoclaved Materials Modified by Glass Sand

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 408
Author(s):  
Anna Stepien
Keyword(s):  
Computed Tomography ◽  
Building Materials ◽  
Micro Ct ◽  
Structure Building ◽  
Acoustic Insulation ◽  
Ct Analysis ◽  
Glass Sand ◽  
Aerated Concrete ◽  
Wall Construction ◽  
Dominant Phase

This paper describes the use of glass sand in the production of autoclaved bricks. Traditional autoclaved materials consist of SiO2, CaO, and H2O. The purpose of the tests is to analyze the possibility of using glass sand in autoclaved materials and to determine their properties and durability. Depending on the structure, building materials can have porosities ranging from 0% (glass, metals) to over 90% (thermal insulation materials such as aerated concrete). Porosity of materials is directly related to the strength of materials and their density, and further to the thermal and acoustic insulation properties of products used especially for external wall construction, i.e., bricks, concrete, and aerated concrete. This type of silicate brick is formed at a temperature of 203 °C, therefore the dominant phase forming the microstructure is tobermorite, in contrast to the C-S-H phase, which dominates in concretes and which is characterized by a larger specific surface. The nature of pores, their number, appearance and arrangement in the material can be studied using computer techniques (SEM, XRD, computed tomography, porosimetry). Computed tomography (micro-CT analysis) showed that the number of voids in the material modified by glass sand is about 20% in relation to the weight of the product. The density of the product with glass sand was determined to be 2.2 kg/dm3.

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