The authors conducted the analysis of scientific and technical references relating to the issue of increasing maintenance reliability of pre-stressed reinforced concrete by means of taking into account concrete non-homogeneity in the calculations of strength, deformability and crack resistance of the reinforced concrete products with annular section. The authors stated the opportunity to increase the quality of concrete intended for centrifugation by means of regulating the properties of used materials. It was identified that applying disperse-reinforced fibers resulted in increase in bending tensile strength, decrease in shrinkage, increase in crack resistance and material resistance towards alternate freezing and thawing, drying and humidification cycles. Upon the results of conducted research and comparison of the properties of various fibers, the authors obtained regularities and application rules on fiber use and gave recommendations in terms of applying one of another fiber type. On the basis of the analysis of obtained results the authors made the conclusion that the highest effect in all tests was observed at the application of basalt fibers as they provide for a higher dispersion of cement rock reinforcement while the basalt fiber itself has a higher strength comparing with any other polymer fiber. Further, the authors conducted the research of mechanical properties characteristic for test beams made of heavy concrete to manufacture the annular section products by means of centrifugation. The obtained dependences allow making a conclusion that the percentage ratio of applied crushed stone fractions Fr 5-10 / Fr 5-20 = 50 / 50 under otherwise equal conditions has the highest influence on the heavy concrete ground strength.

The effect of the multifunctional supplement Linamix PCX and mineral fillers of microsilica and expanded clay dust on the characteristics of concrete mixtures pumped by concrete pumps is investigated. The evaluation of highly mobile and self-compacting concrete mixtures’ properties was carried out according to pumpability criteria that simulate the elastic-viscous structured system flow. The physical and mechanical characteristics of the hardened concrete were determined using standard and generally accepted methods. The ability of the modified concrete to resist tensile stresses was determined by the crack resistance coefficient. The water-reducing efficiency of the superplasticizer was evaluated by the specific consumption of cement per unit of concrete strength. The performed studies have established that the polyfunctional superplasticizer Linamix PCX is an effective modifier of concrete mixtures, rheologically compatible with cements of various material composition. A significant effect of the fine aggregate grain size composition on the properties of highly mobile concrete mixtures and the formation of the hardened concrete structure has been revealed. Evaluation of the modified concretes’ strength characteristics showed that it is rational to use the mixtures with Linamix superplasticizer PCX and microsilica, providing high strength concrete with a minimum specific consumption of cement for concreting massive monolithic structures in order to slow down heat generation during concrete hardening.

Improvement of rural settlements is an urgent task to create attractive living conditions, preserve cultural traditions, develop ethnic tourism and create a unique look for the villages and villages of the Don region. It is advisable to make small architectural forms of concrete, which is a versatile and durable material that allows any designer’s creative idea to be realized. The performed studies have established that it is rational to produce small architectural forms from fine-grained self-compacting mixtures with screenings of stone crushing of rocks of the Don region. The experiments have shown that in a fine-grained self-compacting mixture, the optimal dosage of ordinary limestone crushing screenings is 20%, and sandstone crushing screenings can reach 33%. This is explained by an increase in the liquefaction effect of the anionic superplasticizer due to its lower adsorption on fine particles of sandstone grains, which have a predominantly negative surface charge. The mobile production of small architectural forms from fine-grained self-compacting concretes with stone crushing screenings on the territory of crushing and sorting plants will allow organizing a promising business and creating new jobs for residents of rural settlements.

No abstract

The article covers the processes that occur during centrifugation and vibration centrifugation of ready-mix concrete. It dwells upon the conditions of specific (variational) structure formation of as-formed centrifuged concrete, the outer layer of which is formed mostly by coarse aggregate with an interlayer of cement-water paste; the closer to its inner surface, the higher the content of small particles of dense aggregate and cement-water paste. Having conducted the research, the authors plotted and analyzed stress-deformation diagrams of concrete samples and their separate layers acquired through various molding processes. They studied different concrete mixes with varied combinations of aggregate and dispersed fiber. A mix of vibration centrifuged concrete with combined aggregate (granite + lightweight expanded clay aggregate) and combined fiber (steel + basalt) was chosen for further research. One diagram was plotted for vibrated concrete, which has an even distribution of properties over the cross sections; three diagrams were plotted for centrifuged and three – for vibration centrifuged concrete (one for each layer: outer, middle, and inner). The experimental data was analyzed.

No abstract

No abstract

No abstract