Compact and Loosely Bound Structures in Light Nuclei

A role of different components in the wave function of the weakly bound light nuclei states was studied within the framework of the cluster model, taking into account of orbitals "polarization". It was shown that a limited number of structures associated with the different modes of nucleon motion can be of great importance for such systems. Examples of simple and quite flexible trial wave functions are given for the nuclei $^8$Be, $^6$He. Expressions for the microscopic wave functions of these nuclei were found and used for the calculation of basic nuclear characteristics, using well known central-exchange nucleon-nucleon potentials.Comment: 19 pages, 3 ps figure

Сement based compositions with complex modifying additives based on glyoxal

Introduction. Due to the multicomponent composition, cement based concrete has a high potential for improving technical characteristics by controlling technological processes or the quality of raw materials, which makes it possible to develop composites with specified requirements for the construction of modern resource and energysaving buildings, including for the northern territories of Russia. With the transition to the micro level of the formation of the structure of cement based concretes, new opportunities open up for the directed regulation of properties. Based on this, in order to improve the quality of concrete by improving the structure of the hardened cement paste, a method was proposed for introducing modifiers into the mixture, which directly affect the new growths in the ‘cement-water’ system, which makes it possible to control the process of structure formation of the hardened cement paste.Materials and methods. Research has been carried out using test methods set out in national standards and physical and chemical analysis: thermal analysis and scanning electron microscopy. The results of a study of the effect of complex modifying additives (CMA) based on an aqueous solution of glyoxal and organic acids on the rheological and strength properties of hardened cement paste are presented, the regularities of the processes and the mechanism of structure formation of the modified cement paste are determined.Results. The optimal compositions of a cement based composition based on an aqueous solution of glyoxal have been determined. On the first day of hardening of hardened cement paste with CMA, including polylactic acid and an aqueous solution of glyoxal, as well as lactic acid and an aqueous solution of glyoxal, the strength increases by 23.5%, and at 28 days of age - up to 63% compared to the control composition. Physicochemical studies found that in hardened cement paste with CMA based on an aqueous solution of glyoxal and organic acids, the density and homogeneity of the structure increases, and the content of low-basic hydrosilicates also increases.Conclusion. The developed complex additives are recommended for use in the production of cement based concretes with the required rate of structure formation and high strength

Formation of porous structures in production technology of construction materials based on building gypsum plaster

ABSTRACT: Introduction. This article presents the results of the research works on formation of building gypsum plaster porous structure with the use of recovered anhydrite raw materials and chemical additives, and describes a method for production of wall materials. The relevance of this paper is stipulated by the need to expand the range and increase the manufacture of heat-insulating and structural-heat-insulating products based on gypsum binders and local mineral raw materials, as well as the development of technologies to ensure the production of gypsum materials with improved performance. The authors proposed certain methods for forming the porous structure of building gypsum plaster and improving its performance in terms of porosity and thermal conductivity through the use of modified recovered raw materials and chemical additives of calcium chloride and sodium carbonate. Materials and methods. The study of the effect of modifying additives on the properties of the mixture was carried out using gypsum paste of normal consistency (NC = 55%). The preparation of samples and testing were performed according to the methods specified in the national standards with the use of porous additives of calcium carbonate, fluoroanhydrite and chemical additives for the rheological properties of the mixture, average density and strength of the samples, the patterns and mechanism of the processes of gypsum stone structure formation were established. Results. The application of fluoroanhydrite modified in the disintegrator with an equimolar amount of calcium carbonate leads to a decrease in the average density of the samples to 40% with evenly distributed pores. The analysis of the microstructure of heat-insulating material samples with a density of 550 kg/m3 showed that the average diameter of micropores is 0.45 mm, while the thermal conductivity of samples with complex chemical additives has the thermal conductivity coefficient of 0.25 W/m°C, which is 30% lower than the thermal conductivity of samples without complex additives. Conclusions. The results obtained create the basis for using recovery raw materials and domestic modifying additives as a pore-forming agent, which allow regulating the structure of gypsum stone in order to produce effective wall material

The deformation characteristics of the modified heat-insulating foam concrete

Abstract The present paper investigates deformation characteristics of natural hardened cement based foam concrete with chrysotile asbestos fibers and crystalline glyoxal. The given study is relevant as new methods for managing volumetric changes during the porous cement compositions operation are required to be developed. These new methods should allow obtaining high-quality, energy-efficient wall structures for application on the territory of the Russian Federation. Chrysotile asbestos fibers and crystalline glyoxal applied within the technology of cement foam concrete of natural hardening contribute to ensuring the increased deformation characteristics of concrete at the age of 28 days. The optimal compositions of heat-insulating foam concrete with the elastic modulus of 1035-1383 MPa, Poisson’s ratio of 0.1127-0.1446 and shear modulus of 465-604 MPa have been developed. The elaborated composition and technology of foam concrete production with glyoxal-containing additives is intended for use in the wall structures as well in monolithic construction as in pre-cast production.</jats:p

Сement based compositions with complex modifying additives based on glyoxal

Introduction. Due to the multicomponent composition, cement based concrete has a high potential for improving technical characteristics by controlling technological processes or the quality of raw materials, which makes it possible to develop composites with specified requirements for the construction of modern resource and energysaving buildings, including for the northern territories of Russia. With the transition to the micro level of the formation of the structure of cement based concretes, new opportunities open up for the directed regulation of properties. Based on this, in order to improve the quality of concrete by improving the structure of the hardened cement paste, a method was proposed for introducing modifiers into the mixture, which directly affect the new growths in the ‘cement-water’ system, which makes it possible to control the process of structure formation of the hardened cement paste.Materials and methods. Research has been carried out using test methods set out in national standards and physical and chemical analysis: thermal analysis and scanning electron microscopy. The results of a study of the effect of complex modifying additives (CMA) based on an aqueous solution of glyoxal and organic acids on the rheological and strength properties of hardened cement paste are presented, the regularities of the processes and the mechanism of structure formation of the modified cement paste are determined.Results. The optimal compositions of a cement based composition based on an aqueous solution of glyoxal have been determined. On the first day of hardening of hardened cement paste with CMA, including polylactic acid and an aqueous solution of glyoxal, as well as lactic acid and an aqueous solution of glyoxal, the strength increases by 23.5%, and at 28 days of age - up to 63% compared to the control composition. Physicochemical studies found that in hardened cement paste with CMA based on an aqueous solution of glyoxal and organic acids, the density and homogeneity of the structure increases, and the content of low-basic hydrosilicates also increases.Conclusion. The developed complex additives are recommended for use in the production of cement based concretes with the required rate of structure formation and high strength.</jats:p