English English

Nedoseko I.V.

Doctor of Engineering Sciences (Advanced Doctor), Professor of Building Constructions Department, Ufa State Petroleum Technological University, Russia

Strengthening of monolithic concrete slabs against pushing

https://doi.org/10.58224/2618-7183-2025-8-2-4
, , , ,
Abstract
Significant stress concentrations occur at the interface of floor slabs and columns in widely used monolithic reinforced concrete beamless frames. Therefore, the strength of the floor slabs must be checked for pushing under the loads from columns, bearing walls or stiffening diaphragms. The analysis of engineering solution of beamless monolithic reinforced concrete slabs of the administration nine-storey building with frame-walled load-bearing system is made. The strength thereof for pushing is found to be not provided under the given loads in a number of cases, due to this, experimental studies of strengthening the near-column areas of floor slabs have been carried out. When restoring the structures that suffered defects and damages in the course of their operation, composite materials having high tensile strength, low weight, constructibility and resistance to aggressive influence are widely used. The presented method for strengthening the near-column areas of floor slabs for ensuring their pushing strength with the use of chemical anchors has been developed, and a comparative analysis of the calculation results of the near-column areas of floor slabs with the adopted strengthening method with the results of experimental studies of slab fragments has been carried out. The operating conditions of the near-column areas of the floor slab have been simulated under the test method, and the results of the experimental samples testing are presented. All samples were found to have been destroyed by pushing through, with the destruction being of a plastic nature. The results of assessing the application of transverse reinforcement to the load-carrying capacity of the slab on pushing-through are presented. The results of experimental studies on assessing the pushing strength of extreme parts of monolithic floor slabs with columns reinforced with transverse glued-in reinforcement have shown good efficiency.
PDF

Investigation of structure and properties of expanded clay waste with the purpose of their use in the construction industry

https://doi.org/10.58224/2618-7183-2025-8-1-4
, , , ,
Abstract
This paper describes the structure and properties of large-tonnage expanded clay gravel waste, which is generated as dust from the cyclone, or clay dust (when drying granules), and expanded clay dust from filters (when leaving the kiln, from the cooler and screen). The mineralogical and phase composition of expanded clay dust and its hydraulic activity were determined. Clay dust from cyclones corresponds to the specific surface of 2500 cm2/g, and expanded clay dust from filters - 6800 cm2/g, which allows us to recommend it for use as a fine mineral additive to cement mortars and concretes. Due to the fact that the bulk density of clay dust is about 1000 kg/m3, and expanded clay dust - 6300 kg/m3, it allows to recommend it in the form of facilitating raw material additives in the production of wall and partition products. The results of X-ray phase analysis of clay dust from cyclones showed the presence of significant residues of unburnt clay (more than 80%), and the analysis of expanded clay dust from filters showed the presence of solid high-temperature phases consisting of: Quartz (SiO2) – 50.28%, Albite C-1 (NaAlSi3O8) – 14.82%, Microcline maximum (KAlSi3O8) – 15.73%, Lime (CaO) – 2.77%, Calcite (CaCO3) – 5.11%, Alunogen (Al2(SO4)2(H2O)22) – 11.29%. Hydraulic activity of clay and expanded clay dust according to the methods of GOST R 56593 and GOST 30744 showed that it is extremely low, especially for clay dust (0.3 MPa). On the contrary, the characteristics of samples of clay-alkali compositions showed sufficient strength (for clay dust up to 6.8 MPa, and expanded clay dust up to 3.6 MPa), which allows them to be recommended as a component of slag-alkali binder for cement-soil bases of highways.
PDF

The effect of the temperature difference in the thickness of three-layer reinforced concrete enclosing structures in the operational stage on their stress-strain state

https://doi.org/10.58224/2618-7183-2025-8-1-5
, , ,
Abstract
In three-layer reinforced concrete structures, the inner and outer layers of concrete of different physical and mechanical characteristics have different coefficients of thermal conductivity and linear temperature deformation. During the operation of buildings and structures, due to the temperature difference in the thickness of the structure along the contact planes of the layers, shear stresses may occur, which leads to bending of the structure, an increase in its deflections and a decrease in crack resistance. In this regard, when designing and calculating such structures, it is necessary to take into account the operational stresses and deflections caused by the temperature difference in the thickness of the enclosing structure.
Taking into account the fact that the cross-section of three-layer enclosing structures with a monolithic connection of layers includes various types of concrete and reinforcement, differing in the values of the initial modulus of elasticity, to solve the problem, the cross-section of the enclosing structure is reduced to a homogeneous one corresponding to the largest initial modulus of elasticity of the concrete of the outer layers.
Studies have been carried out to identify the effect of the thickness of the enclosing structure on the change in deflection, depending on the temperature difference, and its share in the total deflection of the structure. Despite the fact that the calculation results revealed a slight increase in the total deflection, taking into account the proportion of deflection that depends on the temperature difference, the study allows us to increase the accuracy of the calculation. The tendency to reduce the material consumption of structures and, consequently, a decrease in the thickness of the structure can lead to an increase in the proportion of deflection, depending on the temperature difference, which must be taken into account when choosing design solutions.
PDF

Study of the characteristics of pavement elements made of rein-forced soil with the use of secondary resources

https://doi.org/10.58224/2618-7183-2023-6-6-2
, , , , , , ,
Abstract
The importance of using secondary resources on the basis of industrial waste is understood by both governments of developed countries and business (production of Portland cement using ground metallurgical slag as a mineral additive at Novotroitsk, Magnitogorsk, Sterlitamak, Katav-Ivanovsk and other plants in the South Urals). The use of secondary raw materials requires the creation of technological infrastructure for processing of secondary raw materials, the costs of which can be quickly recouped due to the cheapness and availability of industrial secondary raw materials and freeing the territory from environmental pollution. In order to recoup the costs of the infrastructure, it is necessary to guarantee full compliance of the quality of pavement elements with the requirements of GOST R 59120-2021. Secondary raw materials have a great variety and laboratory analysis of the quality of pavement elements is required in order to design compositions with the best quality, satisfy-ing all regulatory requirements. In our work the authors present the results of laboratory research and evaluation of the possibility of using clinker-free lime-slag binder based on the mineral product of so-da production and metallurgical slags to strengthen and stabilize soils for their use in pavement struc-tures in the construction of roads for various purposes and climatic zones.
It is experimentally shown that the addition of lime-slag binder in the amount of 8-10% of the dry weight of both cohesive (loamy soil, loamy sand) and non-cohesive (fine sand) soil allows to obtain reinforced soil with improved strength and elastic-deformative characteristics, which can be used in-stead of scarce natural crushed stone and gravel in the construction of underlying layers of pavements in the construction and reconstruction of highways. This technology can be used not only in the Rus-sian Federation, but also in a number of other countries, including those with hot dry climates (e.g., the Republic of Egypt).
PDF

Dry mixes on gypsum and mixed bases in the construction of low-rise residential buildings using 3D printing technology

https://doi.org/10.58224/2618-7183-2023-6-6-5
, , , , , ,
Abstract
3D-printed building construction technology is developing in most countries, such as France, China, Russia and others, and the dry mixes and equipment used are being improved. The development of 3D-printing construction technology is dictated by its many advantages: architectural diversity, speed and automation of the technological process of construction of buildings and structures with a noticeable reduction in the cost of production. However, there are a number of problems of this technology that are waiting for optimal solutions. The paper proposes solutions to two such problems: firstly, the choice of mixture with gypsum and gypsum-cement binders, ensuring the continuity of the 3D printing process of the building and allowing the construction of buildings up to three floors with sufficient safety margin, high seismic stability, as well as with good heat and noise insulation; secondly, the design of buildings with a rational structural and technological solution of the roof and floor, allowing the interface of these structures with load-bearing printed walls.
Different compositions of dry mixes were tested in a series of field tests of large-sized wall blocks made with the use of a construction 3D-printer and filled with especially light porous expanded claydite, expanded clay concrete or heat-insulating foam gypsum with subsequent testing on press equipment of increased load-carrying capacity (with determination of bearing capacity and deforma-bility of the large-sized block).
When designing low-rise buildings, erected by additive technology, as an optimal design of floors, it is proposed to use frame-monolithic beam structures made of metal thin-walled steel galvanized profiles, filled with foam gypsum mix, providing heat and noise insulation and covered with a thin layer of high-strength self-leveling gypsum mix, providing the necessary structural strength of the floor and, accordingly, the minimum load on the foundation.
PDF