Wood fiber and its products are modified to increase fire and bio-resistance. The best results are achieved by using modifiers that enter into chemical interaction with the hydroxylated substrate, forming the organic matrix of the materials. The purpose of the research described in the article was to study the possibility of using boron-nitrogen compounds to modify cellulose and cellulose-containing materials to improve the performance, bio- and fire-protective properties of construction materials, as well as to optimize the consumption of boron-nitrogen compounds. As a result of the research, it was found that the boron-nitrogen compounds used in the compositions developed here chemically interact with hydroxyl groups at the C⁶-atom of cellulose. The chemical interaction of boron-nitrogen compounds with cellulose is an inter-crystalline process occurring without destruction of the crystal structure of the substrate since the modifier molecules bind with the more accessible hydroxyl groups of the amorphous regions of cellulose. Thus, surface modification with boron-nitrogen compounds does not result in accelerated aging of cellulose-containing materials and loss of strength but, on the contrary, increases the durability of wooden structures.

The article is devoted to the questions of usage of crushed concrete fines from concrete scrap for the production of high-quality decorative composite materials based on mixed binder. The main problem in the application of crushed concrete in the manufacture of decorative concrete products is extremely low decorative properties of crushed concrete fines itself, as well as concrete products based on them. However, crushed concrete fines could have a positive impact on the structure of the concrete matrix and could improve the environmental and economic characteristics of the concrete products. Dust fraction of crushed concrete fines contains non-hydrated cement grains, which can be opened in screening process due to the low strength of the contact zone between the hydrated and non-hydrated cement. In addition, the screening process could increase activity of the crushed concrete fines, so it can be used as a fine aggregate and filler for concrete mixes. Previous studies have shown that the effect of the usage of the crushed concrete fines is small and does not allow to obtain concrete products with high strength. However, it is possible to improve the efficiency of the crushed concrete fines as a filler due to the complex of measures prior to mixing. Such measures may include a preliminary mechanochemical activation of the binder (cement binder, iron oxide pigment, silica fume and crushed concrete fines), as well as the usage of polycarboxylate superplasticizers. The development of specific surface area of activated crushed concrete fines ensures strong adhesion between grains of binder and filler during the formation of cement stone matrix. The particle size distribution of the crushed concrete fines could achieve the densest structure of cement stone matrix and improve its resistance to environmental effects. The authors examined the mechanisms of structure of concrete products with crushed concrete fines as a filler. The results of studies of the properties of the crushed concrete fines were provided. It is shown that the admixture of the crushed concrete fines has little effect on the colour characteristics of the decorative concrete products. The preferred options to improve the surfaces of decorative concrete are also proposed.

The formation of concrete structures by spraying method is widely used in the construction of underground structures. The technology of sprayed concrete (otherwise known as shotcrete) is widely used for fixing underground development, in the device of permanent lining of tunnels and collectors, as elements of shells and supporting structures of underground structures of urban infrastructure. Sprayed concrete makes it possible to widely vary the shape and thickness of design of underground structures, allowing to eliminate formwork and in some cases reinforcing. The creation of shotcrete structures with increased physical and mechanical properties, as well as technological parameters should be carried out taking into account the latest achievements in the field of construction materials science. The authors investigated the opti-mized compositions of sprayed concrete in which modified compound with optimally selected granulometric and mineralogical composition and the introduction of fiber into the concrete mixture are used as a binder. Due to the use of different degrees of stability in underground structures with a con-taining soil mass, the requirements for the characteristics of the spray tone can vary widely. Taking into account the spread of the " wet " method of spraying (where the finished concrete mixture is fed to the nozzle at a high speed), special requirements are placed on the rheological characteristics of the mixture and the deformation characteristics during bending (since the bearing capacity of the vaulted coatings depends directly on their ability to withstand loads in stretched zones), especially for lining of hard contour.

The paper presents the blast furnace slag properties at different grinding times by the dry grinding method. The process of fine grinding blast furnace slag is prepared at different times (10 minutes, 20 minutes, 30 minutes, 40 minutes). The results indicated that the main component in BFS is the amorphous structure defined in about 25÷35 degrees (with the appearance of Akermanite at 31.1, Calcite at 29.2 and Aragonite at 26.4). The results also showed that the compressive strength and activity index of blast furnace slag increased significantly after extending the grinding time from 0-40 minutes (corresponding to compressive strength from 51.2 ÷ 7 2.1 MPa at 28 days of age and activity index of blast furnace slag from 91.92% -129.44%). The fine grinding process shows that the particle size of blast furnace slag is significantly reduced. In addition, the paper also presents the effect of finely ground blast furnace slag in 40 minutes on foam concrete properties. Research results show that the use of finely crushed blast furnace slag by the mechanical grinding method to replace sand in foam concrete not only improves the mechanical properties such as compressive strength, flexural strength, the elastic modulus of foam concrete but also protect the environment, reduce product costs.

The paper presents a one-stage method of development results to obtaining effective structural and thermal insulation products based on cellular concrete with variatropic structure and the study of their properties. In addition, the paper presents the study's results on determining the influence of initial components quantitative ratio of the foam-aerated concrete mixture and technological regimes. For this purpose, a model system [Ca(OH)2;Al;H2O;NaF] has been created. The effect of the foam-aerated concrete mixture's form filling ratio (1.0÷0.7) and the perforation index of the form walls on the formation and properties of cellular concrete with a variatropic structure is studied. Influence of variatropic structure of cellular concretes on strength characteristics of products based on them is studied. It is confirmed that products based on cellular concrete with variable density from the periphery have sufficiently good thermal insulation properties due to the low density in the central zone. Concurrently, it meets all the required indicators of strength, hardness and erosion resistance due to the high density of the surface layer. At the same time, the absence of a sharp boundary prevents the zone appearance of contractive stresses and condensate accumulation. The experimental results confirm the possibility of obtaining products based on variatropic cellular concrete with the specified properties and producing building products and structural elements with higher strength indicators than similar products based on monotonic cellular concrete while maintaining material intensity.