The results of studies of recycling aggregates obtained by crushing concrete scrap are presented. The heterogeneity of the material received as a result of crushing concrete scrap, complicates the task of selecting the fractional composition of aggregates. The presence of the mortar component in recycled aggregates significantly increases their water demand. This indicates the expediency of their use in a mixture with natural ones. This work aimed at optimizing the granulometry of recycling rubble and sand. Concrete scrap was used for the research. It was represented by destroyed samples of heavy concrete cubes. Standard methods for determining the grain composition and properties of aggregates of concrete, manufacturing and testing mortar mixes were used. It has been shown that recycling rubble of the 5-20 mm fraction has a minimum voidness when it contains 35% of the 5-10 mm grains and 65% of the 10-20 mm grains, which is close to the ratio of these fractions in the initial crushing product. Therefore, it is advisable to use recycling rubble fractions of 5-20 mm without separation into fractions. The rather high content in the recycling sand of grains with a particle size of more than 0.63 mm indicates the feasibility of using it in a mixture with natural fine and very fine sand. A grain-optimized mixture of natural very fine sand (46% of the total mass of mixed sand) and coarse fractions (0.63–5 mm) of recycled sand (54%) is proposed. Should be considered that recycled sand has increased water demand.

No abstract

Sodium silicate binders are a promising binder base for obtaining effective granular thermal insulation materials. Increasing water resistance, first of all, will expand the scope of their application in construction. At the same time, the features of the modification of sodium silicate binders by compounds of polyvalent metals have not been fully studied, the interaction with which leads to the formation of hardly soluble silicates. The purpose of this work was to develop a modifying complex based on a zinc-containing compound - zinc acetate to increase the water resistance and thermal characteristics of the porous granular material. The proposed modifying additive is a complex consisting of zinc acetate and an organic alcohol solvent. It is shown that the properties of porous granular material can be controlled by changing the composition of the zinc acetate solvent. Qualitative and quantitative dependences of the properties of porous granules (strength, water resistance, density, thermal conductivity) on the type of zinc-containing solution and its content in the compositions have been obtained. The concept of the mechanism of formation of sparingly soluble complexes during the modification of sodium silicate binders with zinc-containing aqueous-alcoholic solutions has been developed. X-ray phase analysis showed that the sodium silicate system modified with an aqueous alcohol solution of zinc acetate, in contrast to an aqueous solution of zinc acetate, is completely in an amorphous state. We believe that compounds of the Zn2SiO4H2O, ZnSiO3 type are in the amorphous state. The obtained research results made it possible to determine the rational composition of granular heat-insulating material with increased operational and functional characteristics (ρ = 200-280 kg / m3, λ = 0.052-0.063 W / (m °C), R = 1.3-1.8 MPa, Kr = 0.89-0.92, W = 16- 18 %).

Methods of recycling polyethylene terephthalate waste are analyzed. Thermoplastic waste has great potential for mechanical recycling. Lack of information on the quality of recycled products and their applicability for specific purposes hinders their use. Shredding is a main process in mechanical recycling. Due to the viscoelastic properties, the cost of grinding polymer waste is several times higher than for most brittle mineral materials. Cutting and impact equipment is often used to shred plastic waste. To obtain micron-sized polymer particles, the technologies of cryogenic grinding and wet grinding in solvents are used, which is followed by high operating costs. The purpose of this work was to develop an economical method for producing fine powders from polyethylene terephthalate waste. The specific surface of the powders has been investigated. To investigate the destruction, differential thermal analysis and infrared spectroscopy were used. The technology of secondary mechanical recycling is proposed: crushing, melting of waste, natural or water cooling of the melt, grinding on equipment typical for brittle materials. A dispersed product with a proportion of micronized fraction of about 50% was obtained for use as filler in composites. The resulting product is more degraded in comparison with the feedstock. Therefore, its use as binders is advisable in applications where a decrease in initial properties is permissible, in products with a long lifecycle, for example, in the production of building materials. The use of waste thermoplastic in applications other than the original one does not always reduce the value of the technology.

The results of studies of the composition and structure of polyethylene terephthalate in the process of thermomechanical processing of polymeric wastes as well as properties of waste products obtained on the basis of waste are presented. Methods of infrared spectroscopy, differential thermal analysis and thermogravimetry, as well as standard methods for manufacturing and testing the technical properties of samples of structural building products were used. As a result of thermomechanical processes during re-melting of polyethylene terephthalate waste, the number of hydroxyl groups in the polymer composition decreases, due to the possible cross-linking and polycondensation of macromolecules through terminal hydroxyl and unactivated carboxyl groups. In this case, conformational rearrangements take place in the structure of polyethylene terephthalate. When thermomechanical processing of secondary PET with rapid cooling of the melt, the temperature of the onset of subsequent melting decreases, which allows to reduce power consumption in melting-mixing units during the process of manufacturing construction products. Construction and technical properties of secondary PET as binder composite building materials allow to obtain potentially durable products with structural strength and high decorative.