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  • A look at the problem of reusing scrap concrete in the construction industry

    Concrete paving slabs for road construction are made from mixtures consisting of hydraulic binder, fine and coarse aggregates and water. The prepared mixture of a given humidity is subjected to vibration molding under the following technological conditions: process duration 5–10 seconds, vibration frequency 30–50 Hz and pressure 70–80 kg/cm2. Hardening of freshly molded samples is carried out in a heat and humidity treatment chamber. It has been established that it is possible to replace natural coarse aggregate with fractionated scrap concrete. The compressive strength of concrete with aggregate based on recycled crushed stone is 300 - 400 kg/cm2, water absorption 4.8 - 6.2%, frost resistance F2 200 - 300. The proposed technology allows solving both economic and environmental issues for regions with large amounts of concrete scrap at temporary industrial waste storage sites.

    Keywords: concrete mixture, vibroforming, modifiers, filler, waste, concrete scrap, strength

  • Expansion of the raw material base for the production of small-piece materials through the use of steelmaking slags

    As a result of artificial carbonization of slag, construction materials can be obtained. For this purpose, a technology has been developed for producing durable construction products as a result of accelerated carbonization of slag minerals with carbon dioxide (CO2) at elevated pressure (up to 2 MPa) and temperatures (20-60°C). The carbonates formed during the carbonization reaction act as a binder, sticking the slag particles together. Carbonized compacts after autoclave processing have technical properties equivalent to conventional concrete products made on the basis of Portland cement. The technology was developed in laboratory and production conditions by optimizing the parameters of the technological process (pressing force, temperature in the autoclave chamber, carbon dioxide pressure in the autoclave chamber and carbonization time) taking into account the increase in compressive strength and frost resistance of the samples.

    Keywords: small-sized products, binder, preliminary preparation, steel slag, pressing, accelerated carbonization, minerals, carbon dioxide, strength, frost resistance

  • Kinetics of strength gain of concrete on a composite binder filled with ground granulated blast furnace slag

    The influence of blast furnace ground granulated slag on the kinetics of strength gain of concrete prepared with a composite binder was revealed. The composite binder contained Portland cement in amounts of 70, 60 and 50%, and the rest was ground granulated slag. It has been established that at the early stage of strength development, concretes made with a composite binder have a strength lower than concrete prepared with Portland cement by 10-24%. However, at the age of 28 days, the strength of concrete using a composite binder corresponds to the strength of concrete using Portland cement. Using polycorboxylate hyperplasticizers, it was possible to obtain concrete with a W/C ratio of 0.25-0.35, which made it possible to obtain high early strength exceeding control compositions by 10-20%.

    Keywords: portland cement, grn slag, grinding, composite binder, kinetics of strength gain, hyperplasticizer, kinetics of strength gain

  • The use of clay brick scrap as a coarse concrete aggregate

    To solve environmental problems related to the disposal of broken bricks, the preparation of new places for building residential complexes, as well as the expansion of the resource base for the production of building materials, clay brick scrap after the renovation of buildings is considered as a major substitute for concrete mixtures. The main physical and mechanical properties of concretes were studied. It has been established that concretes obtained on the basis of coarse aggregate from brick scrap have the properties of concretes based on natural aggregates of the M250-350 grade. The use of scrap clay bricks as fillers requires a special technology for preparing the latter in order to reduce its water demand. The conducted studies have shown that it is expedient to design concrete mixtures based on secondary resources based on a complex binder consisting of Portland cement, finely ground clay brick cullet and hyperplasticizer.

    Keywords: clay brick scrap, coarse aggregate, renovation, binder, hardening, concrete mix, concrete, strength

  • Awakening the hydraulic activity of fillers and aggregates from scrap clay bricks

    The active use in the production of building materials of waste after the renovation of housing is a relevant and promising direction. the load on logistics for the supply of inert materials is reduced, landfills and waste storage sites are being destroyed, and the cost of building materials from recycled materials is being reduced. The use of recycled clay bricks allows to solve the problem of solid waste disposal, but also to reduce the environmental damage caused to the environment by mankind from the excessive development of natural resources. Finely ground brick cullet has pozzolanic properties and can be used as an additive in a cement mixture, and a large fraction is used in aggregates of cement compositions.

    Keywords: Сlay brick scrap, renovation, preparation, pozzolanic activity, hydraulic activity, binder, hardening, aggregate, mortar, strength

  • Applications of fiber in the production of building products

    The aim of the work is to study the possibility of using mineralized fiber as a damping additive in the production of paving slabs and curbs. Fiber mineralization was carried out with an electrolyte solution and sodium silicate. An assessment was made of the physical properties of fiber and their influence on the physical and mechanical properties of fine-grained concrete, hardening both under normal conditions and after heat and moisture treatment. It was revealed that the strength of concretes modified with fiber and hardening under normal conditions is higher than concretes that have undergone heat and moisture treatment by 4.2%.

    Keywords: fiber, organic compounds, sugars, cement clinker, blocking, hardening, hydration, strength, paving slabs

  • Influence of concrete hardening conditions on strength indicators

    Hardening of concrete in the conditions of a construction site under constantly changing temperature and humidity conditions does not provide the desired performance properties of concrete and reinforced concrete structures. An assessment was made of the influence of the conditions of hardening of concrete samples at a water-cement ratio (W / C) of 0.45 and a hardening of 28 days. The hardening of concrete samples took place under conditions of a normal hardening chamber (air temperature T = 20 ± 50С, humidity W = 90 ± 2%), samples in water when completely immersed in a bath at water temperature T = 20 ± 30С and samples immersed in a plastic bag , hardening in the conditions of the air environment of the laboratory (T=20±50C). The samples gain the greatest strength when hardening completely immersed in water, and the smallest when hardening in an insulating polyethylene sheath.

    Keywords: concrete scrap, fractionated crushed stone, water-cement ratio, hardening conditions, clinker hydration, strength development kinetics, moisture migration

  • Influence of ground slag of steelmaking production on the properties of a composite slag-alkaline binder

    The hardening of steel-making slags is slow and the strength properties of the cement stone do not provide the specified operational properties. By creating an optimal composition (steelmaking slag + blast furnace) and chemical activation, a composite material with high strength is obtained. The compressive strength of concrete samples at the age of 28 days of hardening in a normal hardening chamber is 28 to 54 MPa. Caustic soda and sodium silicate were used as a chemical activator of hardening. The greatest strength is provided by the ratio of chemicals as NaOH: Na2 SiO3 × nH2O = 1: 1 and at a dosage of 8% of the mass of the composite slag-alkali binder. The optimum ratio of ground granulated blast furnace slag and steelmaking slag is 3: 1 to obtain high compressive strength and minimum water absorption in the early stages of hardening.

    Keywords: steelmaking slag, blast furnace slag, homogenization, hardening activator, hydration, strength

  • Influence of slag-alkali binder structure modifiers on cracking

    The purpose of the study is to determine an effective modifier of the structure of a slag-alkaline stone, characterized by a low value of linear shrinkage and a decrease in cracking in the early stages of hardening. Ground blast furnace slags were activated with aqueous solutions based on sodium silicate and caustic soda. Fly ash and zeolite-containing clay were used as modifiers of the cement stone structure at a dosage of 5, 10 and 15% of the binder consumption. The results of the study showed that an increase in fly ash content does not significantly affect the setting time. The use of zeolite-containing clay as a slag-alkali binder modifier makes it possible to regulate the setting time of the binder at a dosage of more than 10%. Cracking of the slag-alkaline matrix was observed only for mixtures without fly ash and zeolite-containing clay.

    Keywords: cement stone, slag-alkali binder, hardening activator, structure modifier, fly ash, zeolites, shrinkage, cracking

  • Awakening the hydraulic activity of granulated slag by chemical substances

    The production of Portland cement can be characterized as harmful to nature and human society, resource and energy consuming. The use of by-products of metallurgical and chemical production in obtaining a hydraulic binder is a relevant and promising direction. binder for strengthening and stabilizing the soil of the road base The article investigates the regularities of the initial hardening processes of finely ground slag occurring during structure formation as a result of activation with alkaline solutions and sodium silicates.

    Keywords: granular slag, normal density, setting time, activation, awakening of hydraulic activity, binder, hardening

  • Assessment of the quality of paving slabs based on Portland cement, produced by vibropressing technology

    The physicomechanical properties of paving slabs produced by vibropressing technology are determined. The compositions of fine-grained concrete using quartz fine-grained sands and very fine sands are proposed. The obtained results confirmed the possibility and effectiveness of the use of substandard fine-grained raw materials of the local raw material base, which ensure a reduction in the cost of production.

    Keywords: fine-grained concrete, vibrocompression, raw material base, substandard sands, ground sand, active rheological matrix

  • System perception and transfer of images printing symbols with the original in the matrix of the memorable device of the personal computer, defining types of symbols

    The authors have developed a device consisting of a system of perception of images of printed characters and a personal computer (PC), which determines the types of characters. According to the program developed by the authors, the PC contours the image of the printed symbol in a rectangular matrix consisting of the cells of the PC's storage device. As a result of the edging of the shape of the printed symbol, essential and necessary signs were determined - the directions of the elements of the shape of the symbol, according to which, using the developed algorithm, the PC determined the type of this symbol relative to others. The perception system includes a small-sized television tube - a vidicon with a generator of sweeps of a vidicon beam on its screen vertically and horizontally, two channels and a coincidence circuit. The developed system of perception is distinguished by: simplicity of design, compactness, efficiency.

    Keywords: direction, perception system, trigger, amplifier, pulse counter, coincidence circuit

  • Porous concrete in road construction

    Porous concrete is a new type of concrete with high permeability of water flows. It is advisable to use this type of concrete in road construction for the device filtration zones. This will allow to remove water from the carriageway, especially in places where there is no storm sewer. Infiltration of water flows through concrete pavement coatings contributes to their rapid removal from the surface, reducing slipperiness and water planning. The use of macroporous concrete will minimize flooding of car parks and roads. The results of the study confirm that permeable concrete surfaces function stably over time and are not silted with sand and soil.

    Keywords: porous concrete, permeable surface, filtration, storm sewage, water

  • Investigations of semi-dry pressed concretes made on ultra-fine sands of a local quarry

    The use of ultrathin sand as the main raw material in the production of concrete made by semi-dry molding is relevant for many regions of Russia due to the lack of sand with a high modulus of grain size and solid stone. The article presents the results of the analysis of the possible use of sands with a modulus of particle size Mcr = 0.8-1.4 in pressed small-sized concrete paving products for sidewalks. Replacing ordinary sand up to 80% with fine-grained does not reduce strength and performance properties. The transition to fine-grained and silty sands reduces the cost of production.

    Keywords: concrete, semi-dry pressing, knitting, ultra-fine sand, hyper-plasticizer, strength

  • Levels of management in the construction industry of the national economy as the basis for the stable development of enterprises

    Efficiency, quality and safety of construction are formed by the levels of management and integration relations between the enterprises of the industry and Federal services. Multidirectional construction business contributes to the formation of various types of inter-industry relations. Currently, intra-industry relations are dominant, which are typical for cluster formations in market conditions of development under the existing uncertainty. Effective management of supply and demand affects the stable profit of the construction industry.

    Keywords: construction, management, territorial features, industry features, production, competition, integration associations