scholarly journals Self-repairing of polymer-cement concrete

2013 ◽  
Vol 61 (1) ◽  
pp. 195-200 ◽  
Author(s):  
P. Łukowski ◽  
G. Adamczewski

Abstract Self-repairing means ability to the total or partial recovering of the properties which were worsened as a consequence of damage of the material. The subject of the paper is evaluation of ability to self-repair of a cement composite modified with epoxy resin without a hardener. The methodology of investigation of self-repairing building materials, developed by the authors, has been described, with controllable enforcing of the limited weakening of the material. Also, the self-repair degree has been defined as the measure of self-repairing ability of the building composites. The material model of the epoxy-cement composite has been developed on the basis of the tests results. The material optimization of the composite towards the maximum self-repairing ability has also been carried out. The results of investigation have confirmed the possibility of self-repairing of the cement composite modified with the epoxy resin without hardener. The conclusion and further research needs in the range of the self-repairing epoxy-cement composites have been pointed out

Vestnik MGSU ◽  
2020 ◽  
pp. 1523-1533
Author(s):  
Vladimir T. Erofeev ◽  
Victor V. Afonin ◽  
Tatiana F. Elchishcheva ◽  
Marina M. Zotkina ◽  
Irina V. Erofeeva

Introduction. An engineering method is proposed for assessing salt formation on the surface of cement composites exposed to adverse operating conditions. The technique is based on the histogram method used to determine the dominant brightness of the half-tone image of scanned cement composites. The criterion for ranking composites is a relative dimensionless value –– a metric obtained by comparing the brightness of a grayscale image with the brightness level of white. Materials and methods. We selected three types of compositions of composites in the amount of 21 items; each of them contains three samples –– a control sample and samples exposed to high humidity and positive temperatures for 15 and 45 days. Each composition is represented by a scanned raster image of the sample surface. The images are further subjected to digital processing using a software program written in the C++ programming language and the OpenCV technical vision library. This allows you to use the available methods and classes to develop algorithms to solve the problem in question and to convert a full-color RGB image to a grayscale image. Such images are used to analyze histograms, which determine the dominant level of brightness to determine the numerical metric for quantifying the salt formation on the surface of cement composite samples on the basis of their scanned images. Results. A description of the software algorithm, used to detect salt formation on the surface of cement composite specimens that have passed performance tests under high humidity conditions at positive temperatures, is presented. The method of ranking cement composite samples using the values of their dominant brightness relative to the brightness of control samples is shown. The comparative analysis of the study is presented in the form of numerical data and explanatory diagrams. Conclusions. Software modeling is employed to demonstrate the expediency of the methodology for the assessment of salt formation on the surface of cement composites and other building materials prone to salt formation.


Author(s):  
Qinyue He ◽  
Xun Yu

Hexagonal boron nitride (h-BN) is well known for its unique properties, such as high thermal conductivity, excellent mechanical strength, high electrical insulating, and high chemical stability. This paper studies the effect of h-BN to the mechanical and electrochemical properties of cement concrete. Sodium cholate is used as an ionic surfactant to exfoliate h-BN and subsequently stabilize them in water solution. Different cement concrete samples with different doping levels of h-BN and different sizes of h-BN were prepared for comparisons. Also, steel fiber reinforced h-BN/cement concrete samples were also prepared. The results show that the addition of h-BN can improve the strength of cement composites, and the degree of reinforcement are influenced by the doping levels and feature size of h-BN. The corrosion resistance of h-BN/cement composites were also tested. Experiments results show that h-BN can enhance the corrosion resistance of cement composites.


2008 ◽  
Vol 373-374 ◽  
pp. 714-717 ◽  
Author(s):  
Yi Xin ◽  
Wei Zhang ◽  
Shu Zhang ◽  
Bin Shi Xu

The surface configuration, the size and the shell thickness of the microcapsule were investigated. The average size and shell thickness were 100-200μm and 10nm separately. The mechanism performance of the microcapsule was tested by Nano Indentation Test. The results showed that the shell material—UF behaved as a non-linear viscoelastic material that different from the macroscopical performance. Analyzed and computed the un-load curves by non-linear simulation, the results showed that Educed Modulus of the microcapsule was 8.201GPa, which was a little lower than that of the epoxy resin 9.26GPa. And it also proved that the self-repair microcapsule in the epoxy resin dope would break as the microcrack expanded in the matrix, and let out the repair agent to fill the crack and to recover the matrix.


Author(s):  
Said M. Eshansada ◽  

The development and improvement of the road network is a strategic task of the Islamic Republic of Afghanistan. To develop the sparsely populated territories of the country, it is necessary to build and repair thousands of kilometers of highways, a significant part of which is located in the piedmont and mountainous areas. Considering the fact that the Republic of Afghanistan is characterized by a dry and hot climate, as well as a variety of soil and hydrological conditions, one of the main road building materials for solving this problem is road cement concrete, which has recently become the subject of intensive research. This article presents the results of researching the effect of the Adinol Rapid 2H additive (which is a hardening accelerator additive) on the technological properties of the concrete mixture and the strength of cement concrete.


2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Yun-Wang Choi ◽  
Sung-Rok Oh ◽  
Byung-Keol Choi

We fabricated crack self-healing capsules using cement powder for mixing into cement composites and evaluated the properties of the capsule manufacturing process in this study. The manufacture of the self-healing capsules is divided into core production processing of granulating cement in powder form and a coating process for creating a wall on the surfaces of the granulated cement particles. The produced capsules contain unhardened cement and can be mixed directly with the cement composite materials because they are protected from moisture by the wall material. Therefore, the untreated cement is present in the form of a capsule within the cement composite, and hydration can be induced by moisture penetrating the crack surface in the event of cracking. In the process of granulating the cement, it is important to obtain a suitable consistency through the kneading agent and to maintain the moisture barrier performance of the wall material. We can utilize the results of this study as a basis for advanced self-healing capsule technology for cement composites.


1970 ◽  
Vol 6 (1) ◽  
pp. 202-214
Author(s):  
Олена Савченко

У статті розглядається рефлексивна компетентність як інтегративне особистісне утворення, що формується в ході набуття суб’єктом рефлексивного досвіду при застосуванні різних форм рефлексивної активності, спрямованих на розв’язання визначених рефлексивних задач. У структурі рефлексивної компетентності оцінно-мотиваційний компонент виконує наступні функції: оцінку форм рефлексивної активності та її результатів, прогнозування можливих змін у процесі розв’язування проблемно-конфліктних ситуацій, визначення пріоритетних завдань подальшого розвитку себе як суб’єкта рефлексивної активності. На когнітивному рівні функціонує система критеріїв оцінювання власних форм рефлексивної активності, яка характеризується ступенем когнітивної складності, що відображає рівень диференціації та інтеграції системи. Функціонування оцінно-мотиваційного компонента на метакогнітивному рівні забезпечує система здібностей до прогнозування власної активності. Особистісний рівень представлений системою життєвих задач на саморозвиток, які стимулюють суб’єкта докладати зусилля щодо розвитку в себе певних якостей, формування певних вмінь та знань. Розрізненість елементів компонента є індикатором незавершеності процесу формування його внутрішньої структури, низький рівень інтеграції окремих складових не дозволяє системі ефективно компенсувати недорозвинені елементи. Найбільшу вагу у внутрішній структурі оцінно-мотиваційного компонента має показник сформованості системи здібностей до прогнозування власної активності, що підтверджує системотвірну функцію структур метакогнітивного рівня. In the article the reflective competence is seen as an integrative personal formation which develops in the process of acquiring of the reflective experience, when the subject is using various forms of the reflective activity for the solving of specific reflective tasks. In the structure of the reflective competence the value-motivational component performs such functions: an evaluation of forms of the reflective activity and its results, a prediction of the possible changes in the process of solving of the problem-conflict situations, a determining of the priorities for further development of himself as a subject of the reflective activity. The system of the criteria of an evaluating of the reflective activity`s forms functions on the cognitive level of the reflective competence. The level of the cognitive complexity is the basic feature of this system. The predictive abilities` system, that allows to form the expectations of the activity`s results, presents the value-motivational component on the metacognitive level. The system of the life tasks for the self-development, which stimulates the subject to make efforts to develop his own qualities, to form specific skills and knowledge, functions on the personal level. The fragmentation of the elements is an indicator of the incompleteness of the formation of the internal structure of the value-motivational component. The low level of integration of the separate elements does not allow effectively to compensate the functioning of the unformed elements of the system. The index of the formation of the abilities to predict his own activity has the greatest meaning in the internal structure of the value-motivational component. These data confirm the hypothesis about the system-forming function of the metacognitive structures that unite other structures. Thus the development of the predictive abilities will promote the increase of the abilities to the prediction of the others` behavior. An adequate assessment of other people significantly reduces the inconsistency of his own expectations and estimations of others. The development of the predictive abilities creates favorable conditions for the formation of the life tasks for the self-development to increase their value in the system of other tasks


Author(s):  
Ekaterina Galkina ◽  

The problem of the study is that it is not sufficiently studied what psychological barriers people face at the initial stage of professional activity as self-employed. The aim of the study is to study the features of psychological barriers at the initial stage of professional activity of self-employed people. Research hypothesis: at the initial stage of professional activity as self-employed people face psychological barriers in the organizational and creative areas of entrepreneurial activity. The problem of psychological barriers was considered in their works by S. Rubinstein, N. Podymov, I. Pavlov, R. Shakurov and others. The article formulates particular definitions of the main concepts. Methodology: analysis of an individual case using interviews with processing in the framework of interpretive phenomenology. Respondent: female, 34 years old, self-employed as a psychologist for 1 year. Results: psychological barrier of accepting financial responsibility, barrier of adherence to a certain professional culture, barrier of competence in the profession. Certain psychological barriers can arise in connection with certain underlying medical conditions. The conclusions are that psychological barriers are a complex mental education, can be overcome in stages, and motivation of the subject is important for overcoming barriers.


2018 ◽  
Vol 7 (4) ◽  
pp. 13-21
Author(s):  
Todd Backes ◽  
Charlene Takacs

There are a wide range of options for individuals to choose from in order to engage in aerobic exercise; from outdoor running to computer controlled and self-propelled treadmills. Recently, self-propelled treadmills have increased in popularity and provide an alternative to a motorized treadmill. Twenty subjects (10 men, 10 women) ranging in age from 19-23 with a mean of 20.4 ± 0.8 SD were participants in this study. The subjects visited the laboratory on three occasions. The purpose of the first visit was to familiarize the subject with the self-propelled treadmill (Woodway Curve 3.0). The second visit, subjects were instructed to run on the self-propelled treadmill for 3km at a self-determined pace. Speed data were collected directly from the self-propelled treadmill. The third visit used speed data collected during the self-propelled treadmill run to create an identically paced 3km run for the subjects to perform on a motorized treadmill (COSMED T150). During both the second and third visit, oxygen consumption (VO2) and respiratory exchange ratio (R) data were collected with COSMED’s Quark cardiopulmonary exercise testing (CPET) metabolic mixing chamber system. The VO2 mean value for the self-propelled treadmill (44.90 ± 1.65 SE ml/kg/min) was significantly greater than the motorized treadmill (34.38 ± 1.39 SE ml/kg/min). The mean R value for the self-propelled treadmill (0.91 ± 0.01 SE) was significantly greater than the motorized treadmill (0.86 ± 0.01 SE). Our study demonstrated that a 3km run on a self-propelled treadmill does elicit a greater physiological response than a 3km run at on a standard motorized treadmill. Self-propelled treadmills provide a mode of exercise that offers increased training loads and should be considered as an alternative to motorized treadmills.


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