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Vol. 3 Issue 6

Archives Journal Construction Materials and Products Vol. 3 Issue 6

INCREASING IN IMPACT VISCOSITY OF FIBER-ASH-CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-6-5-16
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 5-16 p.
Abstract
The trend in building materials science is to replace the different proportions of Portland cement in the binder. Therefore, the paper proposes the principles of controlling the static and dynamic strength of fiber-reinforced concrete, consisting in the complex effect of the hydro-removed ash and slag mix and basalt fiber on the processes of structure formation of the cement composite. A four-stage purification system for the hydro-removed ash and slag mixture has been developed, including disintegration, flotation and two-stage magnetic separation. It was found that the density of the fresh mix from the dose behaves naturally, and the density of solid samples at low doses slightly decreases. High early strength of the developed composites is noted, in particular, for specimens with ASM, one and a half increase in compressive strength is traced in comparison with non-additive specimens. Combinations of "fiber + ASM" with a quadrupling of strength have a significant effect on bending strength. Successful approximations of the compressive strength and bending strength on the ASM dose for different ages (1, 7, 28 days) are traced with the regular behavior of the coefficients in the power dependences. Revealed a multiple increase in the impact strength of the developed compositions. The use of the results will lead to the possibility of designing high-strength concretes, including for special structures.
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INCREASING THE BONDING STRENGTH OF THE PLASTERING COATING TO THE BASE

https://doi.org/10.34031/2618-7183-2020-3-6-17-26
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 17-26 p.
Abstract
The strength of plaster coatings depends on the quality of adhesion of the applied plaster layer with the base. The bases for applying plaster coatings are necessarily prepared, the technology of preparing the bases may differ depending on the coating applied. It is established that the closer the initial structures are in structure, the higher the quality of the plaster coating as a whole. According to geonics, the relationship of structures in building composites is based on basic properties, general physical and mechanical indicators, which equally apply to both the building plaster solution and the base. At the same time, a contact binder is allowed between the base and the plaster layer with similar indicators, the presence of which guarantees reliable adhesion and strength of the resulting coating. The use of plaster solutions on enriched fine substandard sands with complex modified additives makes it possible to improve the technological qualities of the mortar mixture, the physical and mechanical characteristics of plaster solutions and optimize the technology of applying the plaster coating. Successive application of plaster layers on technogenic sands with different size modulus allows creating a base rough coating on the base, which closes the main defects and creates the base for the next layer of plaster solution. The Chechen Republic has extensive reserves of very fine and fine local sands, which in their basic properties are inferior to medium- and coarse-grained sands, but with a rational selection of composition, enrichment of grain composition can be used to produce high-quality construction composites. To enrich the grain composition of fine local sands, it is proposed to use dropouts of concrete scrap crushing, the volumes of which are significant on the territory of the Chechen Republic. Dropout of concrete scrap crushing by chemical composition is suitable for enriching local fine sands and when selecting the composition of the plaster solution increases the physical, mechanical and technological properties of the mortar mixture.
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INCREASING THE RESISTANCE OF MACADAM-MASTIC ASPHALT CONCRETE TO RUT FORMATION DUE TO THE USE OF POLYMER MODIFIERS

https://doi.org/10.34031/2618-7183-2020-3-6-27-34
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 27-34 p.
Abstract
Rutting is an important problem in Russia today. One of the ways to improve the properties of asphalt concrete mixtures and reduce wear on road surfaces is to modify the binder with polymer additives. The aim of the work was to test the selected compositions of MMAC mixtures containing bitumen modified with the addition of sevilene and rubber for rutting resistance, which make it possible to predict the formation of plastic rut. It was revealed that when using sevilen in its composition, with an increase in the concentration of vinyl acetate, the depth of the track increases in comparison with the industrial polymer-bitumen binder. It is shown that with the introduction of a complex additive based on sevilen and rubber into the binder composition, its rutting decreases and the service life of the road surface increases, which indicates a high elasticity of the complex-modified binder. In this work, the calculation of the service life of the coating before the formation of a critical rut requiring repair of the coating is carried out. It was found that in terms of the slope of the rutting curve and the proportional depth of the rut, the compositions with sevilene and rubber are not inferior to traditional industrial PBB.
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RELIABILITY OF REINFORCED CONCRETE STRUCTURES TAKING INTO ACCOUNT THE CONCRETE CREEP FACTOR

https://doi.org/10.34031/2618-7183-2020-3-6-35-43
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 35-43 p.
Abstract
In the process of inspection of reinforced concrete structures being in long-term service, deflections of beams and slabs beyond the standard values are often detected, which is attributable to concrete creep occurring in the case of the early dismantling of shuttering. At the same time, any visual signs of their reduced load-bearing capacity are absent. Taking into account the high degree of uncertainty of the factors influencing the long-term strains of the concrete, the safe service life of such structures can vary within a rather wide range, and its actual value can be assessed only through probabilistic methods of the reliability theory. The paper presents the results of the investigation of the influence of concrete creep caused by the early dismantling of the shuttering on the reliability of prefabricated reinforced concrete floor beams of a three-storey building. The data obtained through the instrumental verification of the mechanical characteristics of the beam materials and their deformed state were used for design modelling. The authors carried out the probabilistic creep analysis of the beam through the method of statistical modelling taking into account the variability of concrete strength for various values of the relative humidity of the ambient air and the age of concrete at the moment of the load application. The statistical characteristics of the stress-strain modulus and the beam deflection values with various levels of probability were obtained. Due to con-crete creep, the safety analysis showed a 2,4 times reduction in the beam reliability index at the service life of a structure of 70 years.
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