The influence of secondary crushed stone on the strength and shrinkage of concrete was studied. The results showed that when granite coarse aggregate is replaced with crushed recycled concrete, the compressive strength of concrete is reduced by an average of 20% and the flexural strength by 3-10%. Concrete on recycled crushed stone has a high shrinkage. The shrinkage of concrete with a minimum consumption of recycled aggregate differs slightly from the shrinkage of concrete on granite crushed stone.

Keywords: demolition waste, concrete scrap, recycling, recycled aggregate, compressive strength, flexural strength, shrinkage

The influence of the ratio of fly ash and blast furnace slag in a geopolymer binder on the properties of concrete hardening during heat and humidity treatment was studied. The article obtained data on the influence of the binder composition on the workability of the concrete mixture, the strength and shrinkage of concrete. The dependences of the influence of hardening temperature and the proportion of slag in the binder on the strength of geopolymer concrete were established. The results obtained made it possible to recommend the studied binder and concrete based on it for pilot industrial production of prefabricated reinforced concrete.

Keywords: geopolymer binder, fly ash, blast furnace slag, concrete, strength, workability, water absorption, shrinkage

The importance of inert mineral additives for the development of modern concrete technology is considered. The results of a study of the influence of the dosage of limestone powder on the consistency and strength of fine-grained concrete with different ratios of its components are presented. It was established that in concretes with a high content of superplasticizer, the proportion of mineral additives in mixed cement is the main technological factor in controlling the strength characteristics of concrete.

Keywords: fine-grained concrete, mineral powder, inert mineral additive, superplasticizer, mix consistency, strength, strength control

The results of a study of the influence of slags from various manufacturers on the spreadability, strength and shrinkage of self-compacting fine-grained concrete are presented. It was found that replacing up to 30% of cement with slag reduces the strength of concrete only in the initial period of hardening. It was shown that the use of slag can significantly reduce the shrinkage of concrete.

Keywords: granulated blast furnace slag, mineral additive, fine-grained concrete, self-compacting concrete, mixture flow, strength, shrinkage

The possibility of reducing the excessive strength of self-compacting high-strength concrete for use in general construction was investigated. As a cement for such concrete, a cement-ash binder was studied, part of which was replaced by an inert mineral additive - microquatz, obtained by grinding quartz sand. It was established that the studied additive at a dosage of up to 30% does not allow to reduce the strength of concrete to the values ​​characteristic of general purpose concrete. It has been experimentally shown that the replacement of a part of the binder with microquartz does not significantly affect the initial modulus of elasticity, but significantly reduces the fast-flowing creep

Keywords: high-strength self-compacting concrete, cement-ash binder, inert mineral additive, microquartz, strength, modulus of elasticity, fast-flowing creep

The advantages of using self-compacting concrete in the technology of precast reinforced constructions that are manufactured on stands with a travelling shuttering were considered. Considering the significant heat losses on the heating of products in this technology, concretes have been studied that harden at low temperatures. It was shown that self-compacting concretes with consumption of 330-450 kg / m3 gaining strength in compression of 20-35 MPa for 16-20 hours at low temperature heating.

Keywords: self-compacting concrete, stand technology, travelling shuttering, disperse filler, superplasticizer, heat treatment, strength

The advantages of using polypropylene fiber in technology of geopolymer concrete were considered. It was established that the use of dispersed reinforcement makes it possible to improve the critical characteristics for this type of concrete: strength, crack resistance and shrinkage. It was shown that an important problem of using polypropylene fiber is obtaining of a homogeneous structure of concrete with fiber. The effectiveness of various ways of introducing polypropylene fiber VSM into fine grained geopolymer concrete mixture was studied. It was found that the most effective way of introducing fiber is pre-mix it with a moistened fine aggregate.

Keywords: "geopolymer, fine-grained concrete, disperse reinforcement, polypropylene fiber, mixing technology, compressive strength, flexural strength, homogeneity, granite, slag "

The paper describes the role of inert mineral additives in concrete technology. It was found that inert mineral additives are expediently use together with superplasticizers for the preparation of concrete mixtures with high workability at low cement consumption. It was shown that the negative effect of inert additives on strength decreases with a decrease in the water-cement ratio due to an increase in the proportion of cement hydration products and a reduction in the pore volume in a cement stone prepared with the use of inert mineral additives. There was established that the most promising direction of using these materials is the production of high-fluidity and self-compacting concretes of low and medium class with high frost resistance, water resistance and corrosion resistance

Keywords: "concrete, inert mineral additive, superplasticizer, workability, strength "

The paper describes the effect of dosage of polypropylene fiber on mixture consistency, flexural strength and compression strength and impact strength of fine-grained concrete. It was established that introduction of fiber leads to a certain decrease of consistency of the mixture, but bleeding are significantly decreases. It was found that the reason for the decrease in strength characteristics of concrete with addition of fiber can be related to heterogeneity of distribution of additive in material volume. Therefore, in order to increase the efficiency of use of fiber, necessary to use methods for preparing mixtures with fiber, which ensure a high uniformity of distribution of the additive in material. It was shown that micro-reinforcement increases impact resistance, even with insufficient quality mixing

Keywords: fine-grained concrete, propylene fiber, flexural strength , compressive strength, impact strength, heterogeneity

The paper describes influence of content of dispersed polymer fiber on mechanical properties of mortar on basis of geopolymer binder. The studies were carried out on a geopolymer binder based on crushed granite and ground-granulated blast-furnace slag . Polypropylene fiber with length of 6 mm at a dosage of 0.22, 0.44 and 0.66% by volume was used as a reinforcing fiber. Dependencies were established for the compressive strength, flexural strength, fracture energy, and density from the dosage of the fiber at various times of hardening. It was established that fiber increases flexural strength and tensile strength of geopolymer mortar. It was shown that investigated fiber is characterized by high resistance to alkaline environment of the geopolymeric stone

Keywords: geopolymer, polypropylene fiber, dispersed reinforcement, compressive strength, flexural strength, tensile strength, resistance in alkaline environment

The paper describes influence of different factors on the hardening kinetics of geopolymer binder on the basis of crushed waste from mining and processing of magmatic rocks. The type and dosage of mineral additives to the binder - granulated blast furnace slag, as well as the composition of the activator hardening, dispersibility of components and curing temperature were investigated as factors determining the development of strength of binders. The analytical dependencies describing the effect of the studied factors on the strength of geopolymer binders were obtained.

Keywords: geopolymer, curing kinetics, waste of production and processing of magmatic rocks, blast furnace slag

The paper describes the results of studies on the effect of the dosage of ground gaize of Penza field and polycarboxylate superplasticizer on the properties of mortar constituent of concrete prepared with the use blended cements, containing Portland cement, fly ash, blast furnace slag and silica fume. The study established the equations the bleeding and segregation of mortar constituent of concrete, as well as its strength at different times depending on dosage of superplasticizer and components of blended binder. The negative influence of gaize on the strength greatly reduces by decreasing the water-cement ratio.

Keywords: blended cement, gaize, blast furnace slag, fly ash, superplasticizer, water requirement, slump flow of mixture, strength

The paper describes influence of the specific surface of the slag additive and silica module of hardening activator of geopolymer binder based on the crushed screenings of granite on shrinkage deformation of mortar component of concrete. It was found that shrinkage of geopolymer binder is most intensively occurs at the early stages of structure formation. Particular importance for the structure formation of geopolymer concrete has shrinkage at the stage of setting and initial strength development that need to be considered by appointment of heat and humidity treatment regimes for factory production of products and structures based on geopolymer concrete.

Keywords: geopolymer, hardening, shrinkage, structure formation, slag, activator curing, grinding waste of crushed granite

"This article presents the results of research shrinkage of Portland cement with the addition of gypsum and alumina cement. A technique for the ultimate shear stress of cement paste on his spreadability on the glass and method of estimation of heterogeneity of the mixture was suggested. It is shown that the definition of the area blurring the mixture with a digital camera, followed by treatment with the results using a graphical editor allows to obtain more accurate data on the limit tension of the mixture and its homogeneity. It was found that binder comprising 78% of portland cement, 21,5% of gypsum and 0,5% of aluminous cement has low shrinkage for 3 days. The optimum dosage of additives gypsum and alumina cement depends on the chemical and mineralogical composition of portland cement. "

Keywords: dry mixes, flooring mixes based on cement binder, mixed binder, alumina cement, gypsum, superplasticizer

The results of research on the effectiveness of a multistage crushing of concrete scrap by the "soft" regime are given. It was found that the processing of concrete scrap by this technology can significantly improve some properties of recycled concrete aggregate, particularly crushability, water absorption, shape factor "average thickness of the grain" and porosity. The result of this treatment is the formation of a significant amount of particulate material. This material can be used as a fine filler in the technology of self-compacting concrete. It was found that self-compacting concrete based on products of crushing concrete scrap has a strength of 50 MPa after 28 days of curing in normal conditions, and more than 70 MPa after one year of storage in dry-air conditions. It was established that received concrete has a lower modulus of elasticity, which should be considered when choosing the fields of its application.

Keywords: self-compacting concrete, concrete scrap, secondary aggregates, multi-stage crushing, crushability, water absorption, elastic modulus