HISTORY OF THE APPEARANCE OF EULER’S FORMULA. ISSUES OF STABILITY OF COMPRESSED REINFORCED CONCRETE ELEMENTS

The article presents a brief overview of the life path of the Swiss mathematician and mechanic Leonard Euler, considers the history of the emergence of the formula for calculating stability, shows options for taking into account the fl exibility of an element in the calculations of reinforced concrete structures, the disadvantages of the Euler curve and the features of its application in relation to structures made of high-strength concrete and concrete hardening under pressure. An example of the result of using a non-linear deformation model in the calculations of eccentrically compressed reinforced concrete elements with the introduction into the algorithm for calculating a coeffi cient that takes into account the eff ect of buckling (defl ection) of an element on its bearing capacity is given.

ELIOSYSTEMS FOR INCREASING THE EFFICIENCYOF THE USE OF SOLAR ENERGY IN CONCRETE TECHNOLOGY

Приведены результаты исследования влияния предложенных гелиосистем для повышения эффективности использования солнечной энергии в технологии бетона. При этом исследованы температурные поля бетона изделий, выдерживаемых под гелиопокрытием с межпленочным переменным сечением (МПС). Изучены влияние модуля открытой поверхности на температурный режим твердения, распределение температуры по сечению. Опыты показали эффективность использования солнечной энергии применением гелиотехнической системы для интенсификации твердения бетона в условиях сухого жаркого климата. The results of the study of the influence of the proposed heliosystems for increasing the efficiency of using solar energy in concrete technology are presented. In this case, the temperature fields of the concrete of products maintained under solar coating and under the MPS were investigated. The effect of the open surface modulus on the temperature regime of hardening, the temperature distribution over the cross section, was studied. The experiments showed the efficiency of the use of solar energy by using a solar system for the intensification of concrete hardening in a dry, hot climate.

INFLUENCE OF WATER LOSS ON STRENGTH CHARACTERISTICS OF HELIOBETON

В работе рассмотрены основы тепло- и массообменных процессов при выдерживании бетона в гелиоформах со светопрозрачным покрытием. Изучены особенности обезвоживания бетона, твердеющего в условиях высоких температур и низкой относительной влажности. Установлено, что количественные показатели влагопотерь влияют не только на физико-механические и эксплуатационные показатели, но и на конструктивные особенности гелиоформ, используемых для выдерживания бетонных композитов на комплексных вяжущих, получаемых на основе использования портландцемента и некондиционного природного и техногенного сырья. The paper discusses the basics of heat and mass transfer processes during the curing of concrete in helioforms with a translucent coating. The features of dehydration of concrete hardening under conditions of high temperatures and low relative humidity have been studied. It has been established that the quantitative indicators of moisture loss affect not only the physical, mechanical and operational indicators, but also the design features of the helioforms used to cure concrete composites on complex binders obtained through the use of Portland cement and substandard natural and technogenic raw materials.

ADDITIVES FOR HEAVY CONCRETE BASED ON INDUSTRIAL WASTE FROM CHEMICAL INDUSTRIES

The effect of a complex additive containing superplasticizer C-3 on the properties of heavy concrete has been investigated. The efficiency of the plasticizing action of the specified additive at the stage of preparation of the concrete mixture and subsequent molding of concrete products has been revealed. It is proved that at the stage of concrete hardening, the investigated additive promotes to the formation of a more homogeneous colloidal-crystalline structure and the formation of dense crystalline hydrate complexes of cement stone by the time of completion of concrete hardening. The objects of investigation were samples of grade B22.5 concrete without additives; containing a monoadditive - superplasticizer S-3; containing the complex additive. When designing the composition of additives for heavy concrete, we proceeded from the fundamental provisions of construction science that the complexity of the action of additives lies in the optimal combination of two main opposite processes in time and volume of the concrete matrix. The use of the caprolactam oligomer synthesized in the course of this investigation makes it possible to solve the problem of involving concentrated wastes of caprolactam production in the production turnover. The obtained caprolactam oligomers can be used in construction as plasticizers of concrete mixtures, as inhibitors of corrosion of steel reinforcement in the production of reinforced concrete products. Water-soluble oligomers of caprolactam, which reduce the time of dissolution of the superplasticizer C-3 and the dispersion of low-temperature catalyst in the volume of the concrete mixture being mixed, were synthesized. It was found that in the presence of the oligomer caprolactam in an amount of 10 to 20% of the mass. the dissolution rate of S-3 superplasticizer in water at a temperature of 20-21 °C increases by 2.0-2.2 times. This contributes to a better mixing of the components of the concrete mixture, primarily to improve the dispersion of the complex additive in the volume of the concrete mixture. The caprolactam oligomer used in this research work is an effective water-soluble wetting agent for the surface of particles of cement, sand, and crushed stone, which is very important for activating hydration and sorption processes during mixing of a concrete mixture. The increased wetting properties of the caprolactam oligomer are characterized by a wetting angle of 19.6 °.

ENERGY-SAVING CHAMBER IN PRODUCTION OF BUILDING MATERIALS AND PRODUCTS

This paper presents the results of a study of the compressive strength of concrete in a cyclic solar chamber. The analysis of the existing types of industrial solar chambers is carried out and the main structural elements are considered. The method of calculating the solar chamber for the production of concrete products is presented. Experiments were carried out on heavy concrete compositions using MC-Bauchemie superplasticizers additives: MC-PowerFlow 3100 and MC-PowerFlow 2695. The samples were kept in a cyclical solar chamber. The strength of concrete was determined at different periods of concrete hardening. A comparative analysis of the results of the compressive strength of concrete in a solar and normal hardening chamber is carried out.

The effect of fine aggregates produced from anthropogenic waste and low-modulus fiber on the workability of self-compacting concrete (SCC)

This article gives information about the research of the new promising material in construction industry of the Republic of Kazakhstan, namely, self-compacting concrete (SCC). We have studied such important physical and technical properties as workability, durability, gain in strength in the early stages of concrete hardening. The data obtained are presented in summary tables, a mathematical model is given, generalizing conclusions are made.

Application of additives-accelerators of cement concrete hardening in the construction of roads in Afghanistan

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.

Thermovision monitoring the heat of hydration in concrete

Due to the Portland cement chemical reaction, which always takes place in a hardening concrete, a certain amount of heat is released. This heat should be quantified, as it can harm or aid the concrete itself, depending on the concrete components, structure element, ambient and building site conditions. There are number of possible setups for the monitoring of heat of hydration, two of which have been applied in the case presented in this paper. Four concretes were monitored with the use of the two stated techniques for 24 hours. First technique used is thermo-vision camera which monitored the surface, and the second is thermosensor - used for monitoring of interior of fresh concrete hardening mass. The potential of the applied setup lays in the ease of installation, low price, and possibilities of mass application, which could substantially aid the monitoring and prevent concrete failure.

Expanded Clay Applications in Internal Curing of Concrete

Internal curing is used to reduce shrinkage and early age cracking of poured concrete. The internal curing process depends on providing internal moisture to hardening concrete using prewetted light weight aggregates, as expanded slates and shales. The main objective of this research is to produce internally cured light-weight concrete mixes to be used in bridge deck construction. Light-weight mixes are developed by incorporating different percentages of pre-wetted expanded clays in partial replacement of mix coarse aggregates. Expanded clays will internally provide the concrete with adequate moisture to account for water evaporating during concrete hardening. Produced concrete mixes are characterized by light weight, comparable compressive strength, and reduced shrinkage and early-age cracking. Produced lightweight mixes showed comparable strength with minimized shrinkage, which will positively impact the durability of concrete