scholarly journals Analysis of the Crack Resistance of the Cement Stone and Roche

2019 ◽  
Vol 50 (2) ◽  
pp. 124-131
Author(s):  
Vladimir Erofeev ◽  
Irina Maksimova ◽  
Nikolay Makridin ◽  
Alexey Bulgakov ◽  
Salman Al-Dulaimi
Keyword(s):  
Crack Resistance ◽  
Influencing Factor ◽  
Limit State ◽  
Practical Importance ◽  
Cement Composite ◽  
Material Structure ◽  
Cement Stone ◽  
Professional Literature ◽  
Actual Strength ◽  
New Generation

The crack resistance is the most important parameter of strength. It characterizes the ability of a material structure to resist the beginning of the movement and development of cracks at mechanical and other force impacts and is the most important parameter of the limit state of the structure. In this regard, the evaluation of parameters of the mechanics of rocks, used as fillers (dispersed phase) and the cement stone (matrix phase) for concrete, influencing factor of the actual strength of the cement composite, is not only of theoretical interest, but also of great practical importance, since the issues in regards to the problem of choosing fillers are very poorly addressed in the professional literature, especially re the new generation of concretes.

scholarly journals Development of lignocellulosic fiber reinforced cement composite panels using semi-dry technology

Cellulose ◽  
2021 ◽  
Vol 28 (6) ◽  
pp. 3631-3645
Author(s):  
K. M. Faridul Hasan ◽  
Péter György Horváth ◽  
Tibor Alpár
Keyword(s):  
Flexural Modulus ◽  
Cement Composite ◽  
Composite Panel ◽  
Bending Test ◽  
Morphological Properties ◽  
Cement Stone ◽  
Composite Panels ◽  
Internal Bonding ◽  
Dry Process ◽  
Lignocellulosic Fiber

AbstractThere is a growing interest in developing cement bonded lignocellulosic fiber (LF) composites with enhanced mechanical performances. This study assessed the possibility of developing composite panels with 12 mm thickness and around 1200 kg/m3 nominal densities from ordinary Portland cements (OPC) and mixed LFs from seven different woody plants found in Hungary. Once the mixed LFs were sieved and found fine (0–0.6 mm) and medium (0.6–0.8 mm) length fibers. The optimum ratio for LF, OPC, water glass (Na2SiO3), and cement stone was found to be 1:3.5:0.7:0.07. The semi-dry process, which is a comparatively cheaper and less labor intensive technology, was used for producing the composites. After 28 days of curing, the composite panels were characterized for mechanical, physical, thermal, and morphological properties. A scanning electron microscopy (SEM) test was conducted to observe the fiber orientation in the matrix before and after the bending test, which showed the clear presence of the fibers in the composites. The FTIR (Fourier transform infrared spectroscopy) was conducted to investigate the presence of chemical compounds of LF in the composite panels. Different physical (water absorption and thickness swelling) characteristics of the composite panels were investigated. Furthermore, mechanical properties (flexural properties and internal bonding strength) of the composite panels were also found to be satisfactory. The flexural modulus and internal bonding strengths of composite panel 2 is higher than other three boards, although the flexural strength is a little lower than composite panel 1. The thermogravimetric analysis and differential thermogravimetry also indicated better thermal stability of composite panels which could be used as potential insulation panel for buildings. Graphic abstract

Some problems of assessing the dynamic crack resistance of structural steels

2021 ◽  
Vol 18 (3) ◽  
pp. 428-435
Author(s):  
Vladimir I. SMIRNOV ◽  
◽  
Tatiana A. KNOPOVA ◽  
Sergey S. MAYER ◽  
◽  
...  
Keyword(s):  
Crack Resistance ◽  
High Speed ◽  
Dynamic Testing ◽  
Practical Importance ◽  
Dynamic Strength ◽  
Structural Steels ◽  
Dynamic Crack ◽  
Unstable Fracture ◽  
Structural Elements ◽  
Limiting State

Objective: Solving the problem of determining the conditions for the onset and development of unstable fracture, which is extremely important for the development of methods for calculating the limiting states of structural elements, improving the dynamic testing schemes of materials and classifying steels according to their ability to resist fracture. Methods: Analytical methods for assessing the limiting state of structural elements are used. Results: A brief overview of the available test methods for structural steels for dynamic strength and crack resistance is given. The experience accumulated by domestic and foreign practices in testing steels for strength and crack resistance under high-speed loading is analyzed. The disadvantages of the existing methods for assessing the indicators of dynamic strength and resistance to brittle fracture are indicated. Practical importance: It is shown that along with the traditional methods for assessing strength based on safety factors, it is necessary to develop and apply new methods for assessing the limiting state of structural elements, including by the criteria of crack resistance

scholarly journals DESIGN OF CEMENT COMPOSITES WITH INCREASED IMPERMEABILITY

Vestnik MGSU ◽  
2016 ◽  
pp. 72-81
Author(s):  
Roman Sergeevich Fedyuk
Keyword(s):  
Composite Materials ◽  
Cement Composite ◽  
Vapor Permeability ◽  
Cement Stone ◽  
Cement Composites ◽  
Hydrated Cement ◽  
Body Density ◽  
Scale Levels ◽  
Positive Effect ◽  
Improved Characteristics

The paper deals with the development of composite binders for producing concrete with improved characteristics of gas, water and vapor permeability. The authors investigate the processes of composite materials formation in order of decreasing scale levels from macro to nanostructures. The criteria for optimization of the volume of dispersed additives in concrete are offered. The authors theoretically studied the technological features of the formation of hydrated cement stone structure. A positive effect of nanodispersed additives on the structure and physico-mechanical properties of cement composite materials are predicted. Thanks to its improved features, such as good ratio of strength and body density, high density and lifetime, the modified concrete may be used when solving various practical tasks of the construction branch.

scholarly journals EXPERIMENTAL FINDING OF FRACTURE TOUGHNESS CHARACTERISTICS AND THEORETICAL MODELING OF CRACK PROPAGATION PROCESSES IN CARBON FIBER SAMPLES UNDER CONDITIONS OF ADDITIVE PRODUCTION

2019 ◽  
Vol 16 (33) ◽  
pp. 325-336
Author(s):  
V. N. DOBRYANSKIY ◽  
L. N. RABINSKIY ◽  
O. V. TUSHAVINA
Keyword(s):  
Fracture Toughness ◽  
Carbon Fiber ◽  
Crack Resistance ◽  
Tensile Properties ◽  
Practical Importance ◽  
Effect Of Temperature ◽  
Zone Model ◽  
Cohesive Elements ◽  
Damage Development ◽  
Mechanical Tensile

The relevance of the problem stated in this article is that the development of aerospace technology increased the demand for good quality materials. An important issue is ensuring durability in conditions of longterm loads and in conditions of damage development. One of the criteria that ensure the toughness of the material is crack resistance. The aim of the work is to study the interlayer crack resistance (fracture toughness) under loading under conditions of separation and transverse shear, interlayer strength, as well as the effect of temperature on interlayer strength, mechanical tensile properties. A comparison of the values of interlayer crack resistance GIС (separation) and GIIС (shear) and of mechanical tensile properties and interlayer strength of carbon fiber samples is made. The main methods for studying this problem were the short-beam method, the DCB method, the ENF method. The results of the experimental data were compared with modeling the processes of the appearance and development of cracks in the finite element complexes ABAQUS and Ansys based on the VVCT models, cohesive elements. Deviations from the experiment were found and conclusions were drawn that the point of application of the load had to be shifted from the edge of the sample, which will reduce the initial separation and increase the stiffness of the sample. Due to the fact that the cohesion zone model is very sensitive to input parameters, it is necessary to know many parameters and take into account a large number of factors. The practical importance of this work is to show how to use the VCCT model to obtain the critical load of the germination of the first crack. The research technique can be used for further experiments, including simulation further stratification with low inaccuracy.

scholarly journals Influence of optimal conditions of ultrasonic dispersion on the stability of suspensions of finely ground slags

2019 ◽  
Vol 265 ◽  
pp. 01017 ◽  
Author(s):  
Svetlana Samchenko ◽  
Irina Kozlova ◽  
Оlga Zemskova ◽  
Ekaterina Baskakova
Keyword(s):  
Aqueous Dispersion ◽  
Cement Composite ◽  
Cement Stone ◽  
Mechanical Mixing ◽  
Dispersion Parameters ◽  
Ultrasonic Dispersion ◽  
Sedimentation Stability ◽  
Granulated Blast Furnace Slag ◽  
The Stability ◽  
Furnace Slag

The preparation in the jet mill of finely ground slag (FGS) from the waste of metallurgical production granulated blast-furnace slag, the obtaining of slag suspensions, and the behavior of FGS particles in an aqueous dispersion medium are considered in the paper. It was found that FGS particles in the suspension form micelles of two types with negative (micelle 1) and positive (micelle 2) charges of FGS surface. To increase the aggregative and sedimentation stability of FGS particles in suspensions, studies were carried out using ultrasonic dispersion. The results of investigations on the detection of optimal dispersion parameters for slag suspensions are presented. It was found that in the absence of temperature control, the process of coagulation of slag particles is accelerated and aggregative and sedimentation stability of suspensions of FGS is reduced. The slag particles in the suspension form aggregates that lead to a deterioration of the strength characteristics of the cement stone using suspensions of FGS. Optimal parameters of ultrasonic dispersion of slag suspensions are established: the frequency of ultrasonic vibrations is equal to 44 kHz; the dispersion temperature is 25 ± 2 °C; the dispersion time is 15 min. It was found that the application of ultrasonic dispersion to slag suspensions with the observance of dispersion conditions can increase the aggregative and sedimentation stability of FGS suspension by 2-3 times in comparison with the mechanical mixing of suspensions. The strength of samples with suspensions of FGS prepared using UST under the recommended dispersing conditions increased by 19 to 39% in the first day; for 28 days of hardening - by 19 - 36%, which allows using slag suspensions in the production of cement composite materials and concretes based on them.

scholarly journals Effect of titanosilicate additives on the strength of a self-cleaning cement stone.

2020 ◽  
Vol 11 (3-2020) ◽  
pp. 209-214
Author(s):  
A. V. Tsyryatieva ◽  
Keyword(s):  
Compressive Strength ◽  
Titanium Dioxide ◽  
Hydrochloric Acid ◽  
Cement Composite ◽  
Cement Stone ◽  
Titanium Oxides ◽  
Self Cleaning

The possibility of modifying cement composite by titanosilicate additive, consisting of the mixture of silicon and titanium oxides (TSP —titanosilicate precipitate), obtained by coprecipitation during the interaction of titanite with hydrochloric acid was studied. The properties of the modified TSP cement composite and mechanically prepared mixtures of titanium dioxide (anatase) with silica and titanium dioxide (rutile) with silica are compared. It has been shown that titanosilicate additives in cement compositions increase the compressive strength and give the surface self-cleaning properties.

scholarly journals INFLUENCE OF THE CEMENT COMPOSITION ON THE PROPERTIES OF REINFORCED CONCRETE STRUCTURES WORKING IN HIGH TEMPERATURE CONDITIONS

Fire Safety ◽  
2018 ◽  
pp. 10-14
Author(s):  
O. Bashynskyi ◽  
M. Peleshko ◽  
S. Vovk ◽  
O. Pazen
Keyword(s):  
High Temperatures ◽  
Solid Phase ◽  
Cement Composite ◽  
Strength Characteristics ◽  
Cement Stone ◽  
Solid Phase Reactions ◽  
Loss Of Strength ◽  
Individual Particles ◽  
Partial Coupling ◽  
Decomposition Of Water

In the article the influence of binder hardening of concrete processes and changes in the phase composition of cement by heating to 1000 °С. It was established that the presence of active mineral adds in cement composite increases the strength of concrete at ordinary temperatures as well as when heated in a fire.  Damage of structures, accompanied by loss of strength characteristics of concrete under the influence of high temperatures of the fire due to the decomposition of water-containing crystalline hydrates, which are formed when locked up with water. The analysis of the results of physical and mechanical investigations of portland cement with applications of meadow waste has shown that their loading allows to significantly increase the strength of this cement stone, due to the formation of an additional amount of sodium sulfate or potassium. Their influence as activators of hardening is most noticeable in the initial terms and gradually decreases with age of hardening. It has been shown that use in the composition of the binder of meadow-based additives and hydrosilics makes it possible to increase the strength of the cement stone by 1.5 times, which is essential for the development of effective composite binders on its basis for work in high temperatures. In this, the presence of fluoride aluminium in hydrosilic in a quantity of 3.3% by weight determines its plastisizing effect on cement. It has been experimentally stated that during the heating of concrete above 500°C, the destruction of hydrated components of cement stone with the destruction of structural bonds between individual particles with a significant decrease in strength characteristics. In this case, the use of applications provides a partial coupling of CaO in the process of solid phase reactions during heating. It is proved that the use of composite cement, as a binder, due to the presence of its composition of a meadow-based application - accelerates hardening and improves strength characteristics, hydrosilics - increases residual strength at a pressure of up to 1000°С by 2.4 MPa .

scholarly journals The Study of Crack Resistance of Concretes of a New Generation

2019 ◽  
Vol 775 (10) ◽  
pp. 3-11
Author(s):  
V.I. TRAVUSH ◽  
◽  
N.I. KARPENKO ◽  
V.T. EROFEEV ◽  
I.V. EROFEEVA ◽  
...  
Keyword(s):  
Crack Resistance ◽  
New Generation

scholarly journals Experimental Study and Numerical Simulation on Mechanical Properties of the Bottom Plate in the Assembled Composite Slab with Additional Steel Trusses

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xiuying Yang ◽  
Yuzhuo Wang ◽  
Yongxin Liu ◽  
Zhenyu Wei
Keyword(s):  
Crack Resistance ◽  
Limit State ◽  
Load Level ◽  
Bottom Plate ◽  
Composite Slab ◽  
Static Test ◽  
Service Limit State ◽  
New Type ◽  
Transverse Steel ◽  
Steel Trusses

The composite slab with steel trusses is composed of precast bottom plate and cast-in-place concrete. In engineering applications, cracks often appear in the bottom plate before casting the upper concrete, which even leads to the failure of the composite slab. To improve the crack resistance of the slab, a composite slab with additional steel trusses is proposed; that is, on the basis of the original longitudinal steel trusses, the transverse steel trusses are added. Static test and numerical analysis were carried out on the bottom plate of the new type of composite slab with the additional transverse steel trusses. The experimental and analytical results show that the load level of the plate with additional steel trusses can be increased by 33% under the normal service limit state; the deflection of the plate is significantly reduced and the crack development is effectively controlled, which illustrates that the new type of composite slab can improve the bearing capacity, increase the bending stiffness, and enhance the crack resistance effectively.

The Effect of Fine Dispersed Slag Component on the Slag Portland Cement Properties

2020 ◽  
Vol 1011 ◽  
pp. 103-108
Author(s):  
Irina Kozlova ◽  
Olga Zemskova ◽  
Vyacheslav Semenov
Keyword(s):  
Portland Cement ◽  
Structural Characteristics ◽  
Initial Period ◽  
Cement Composite ◽  
Cement Matrix ◽  
Cement Stone ◽  
Ultrafine Grinding ◽  
Slag Component

Cement compositions based on slag Portland cement and fine dispersed slag component are considered. It has been established that the introduction of 1-3% fine slag obtained as a result of ultrafine grinding in a jet mill into the slag Portland cement composition provides an increase in the strength and structural characteristics of cement stone from the first day of hardening, which is important for slag cements. To ensure the fine dispersed slag particles’ stabilization in the cement matrix, the cement compositions were sealed with water with the addition of a plasticizer on either sulfa-naphthalene formaldehyde or polycarboxylate substrates in an amount of 0.5% of the cement composite content. In the research course it was found that in the initial stages of hardening and grade age, the strength of the samples containing a fine dispersed slag component and a sulfa-naphthalene formaldehyde-based plasticizer increased by 20%. When the cement composition is mixed with water with a polycarboxylate-based plasticizer, an increase in strength in the initial period of hardening by 60% is noted, at the vintage age - by 30%. At the same time, the porosity of the samples based on slag Portland cement with the addition of fine dispersed slag and one of the plasticizers in the initial period was reduced by 16-21%, at the vintage age - by 33-35%.

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