Introduction. In order to give geometric immutability to load-bearing structures that accept horizontal loads from the wind, it is necessary to introduce rigid nodes into the design scheme. The insufficiency of the regulatory framework for calculating nodes with glued joints leads to a separation of calculations from company to company. This paper proposes a method for designing and calculating a ridge assembly of wooden structures with glued washers.

Materials and methods. Engineering calculation of the ridge node and its elements, modelling and calculation of the considered connection, as well as analysis of the possibility of its application on the example of an existing building, calculated in the SCAD software.

Results. A constructive solution for a new type of rigid assembly was developed based on the use of steel washers glued into wood. A numerical and theoretical analysis of each element of the joint for the forces transmitted by neighboring structures is carried out. Estimation of the numerical order of the bending moment perceived by the proposed design. The bearing capacity of the proposed solution eliminates ductility and increases the strength of the entire joint.

Conclusions. The proposed assembly is lighter than its counterpart on glued rods, and the lack of a regulatory framework for such structures forces designers to make standard decisions. The proposed method for calculating the nodal connection can improve reliability, as well as increase the economic efficiency of the entire structure. The possibility of using the proposed node has been confirmed by numerical modelling methods.

Introduction. The use of mixed binders with an increased content of active mineral additives allows improving a number of the most important physical and mechanical properties of concrete. However, a decrease in the proportion of clinker for structural concrete may negatively affect the durability of the reinforced concrete product and the structure as a whole, due to a potential decrease in the pH of the pore liquid of the concrete. Gypsum cement-pozzolanic binders are materials with a small clinker fund, since gypsum binder, which has an acidic environment, predominates in their composition. Therefore, when introducing load-bearing products and structures into production, it is necessary to check the protective properties of concrete in relation to steel reinforcement.

Materials and methods. To prepare the gypsum-cement-pozzolanic binder, we used gypsum binder of grade G-5, cement binder of grade CEM I 42.5N and pozzolanic mineral additives: natural zeolite, microsilica and fly ash. The pH and ionic concentration values of hydrated suspensions with various active mineral additives, both mono- and binary modifications, were studied using potentiometric and conductometric methods. Compressive strength was estimated after 7, 28 and 90 days of hardening in accordance with GOST 10180–2012; water absorption — according to the method of GOST 23789–2018; water resistance was estimated by the softening coefficient.

Results. As a result of the experiments, a composition of gypsum-cement-pozzolanic binder with high protective and physical-mechanical properties was obtained, which can be used for the production of structural quick-hardening concrete.

Conclusions. The obtained results indicate sufficient protective properties of concrete based on gypsum-cement-pozzolanic binders in relation to steel reinforcement: a pH of at least 12 and a composition containing 60 % gypsum binder, 25 % Portland cement and a binary active mineral additive based on microsilica and natural zeolite in a ratio of 2:1 by weight.

Introduction. In practice, standard technical characteristics (such as cone slump, mixture spread diameter, etc.) are used as indicators of the efficiency of plasticizing additives. However, these characteristics make it difficult to judge the rheological properties of cement systems. This paper is devoted to analyzing the correlation between mobility indicators and rheological characteristics, as well as the regulation of rheological parameters of cement mixtures considering electro-surface phenomena.

Materials and methods. Fine fillers (quartz, marble) with different electro-surface properties (Ssp = 300 and 600 m2/kg) were used. The binder was CEM I 42.5 N produced by CJSC “Oskoltsement”; chemical additives included the superplasticizer Polyplast SP-1 and the superplasticizer Sunbo 2021. Rheological characteristics of the dispersions were determined using a Rheotest RN 4.1 rotational viscometer, and mobility was assessed with a mini-cone. Surface microanalysis was conducted using a TESCAN MIRA 3 LM scanning electron microscope. Specific surface area was measured with a PSKh-10a device, and the electrokinetic potential of particle surfaces was measured using a Zetasizer Nano ZS.

Results. It was shown that the greatest thinning effect was observed in suspensions where the predominant surface charge of mineral filler particles was opposite to the charge of the functional group of anionic plasticizing additives, and vice versa. It was revealed that the type of mineral filler had a stronger impact on mobility indicators than on rheological characteristics. A correlation between plastic viscosity and mobility (spread diameter) was established. Based on the analysis of the obtained rheological data and mobility, flow regions of cement dispersions were identified.

Conclusions. The use of fine powders positively influences the flowability of cement dispersions, with marble filler being more effective than quartz. In the region of moderate dispersion thinning (spread diameter = 60–170 mm), the cone spread is consistent with the rheological properties of cement systems. Practical application of the research results presented in this paper will enhance the efficiency of superplasticizers and superplasticizers and simplify the assessment of the rheological flow regime of dispersions.

Introduction. The present paper shares new results of research devoted to improving the operation of conventional reverse osmosis. A new technological solution is proposed to escape scaling on the membrane surface. Applications of nanofiltration membranes provide a reduction of operation costs connected with chemical purchases to ensure pretreatment and chemical cleaning and also to pay for concentrate discharge into the sewer.

Materials and methods. In the paper, the experimental methods developed earlier were used, such as the evaluation of membrane rejection and control of permeate quality as a function of the initial feed water volume reduction coefficient K; evaluation of calcium carbonate scaling rates and organic fouling rates in membrane modules. The experimentally obtained relationships are presented: dependencies of calcium concentrations and TDS values on the initial volume reduction coefficient K values and product flow reduction with K value relationships. Also, the second series results are presented that demonstrate dependencies of calcium carbonate growth rates on K.

Results. Results of the required numbers of membrane modules are obtained to tailor the 3 cubic metres per hour capacity membrane facility and the results of economic calculations are also obtained.

Conclusions. The use of nanofiltration membranes on each stage of water treatment allows for the escape of deposition of sparingly soluble salts on the membrane surface and excludes antiscalant dosing and routine membrane cleanings. The use of the developed technology featured by the low operational cost due to reduced reagent consumption and concentrate discharge into the sewer.