Сравнительный анализ расчета коэффициента интенсивности напряжений по результатам равновесных и неравновесных испытаний

Sadovskaya E. A., Leonovich S. N.Сравнительный анализ расчета коэффициента интенсивности напряжений по результатам равновесных и неравновесных испытанийThis article explores the practical use of methods for determining the stress intensity factor at normal separation: eccentric compression of notched cubes and four-point bending of a notched beam. During non-equilibrium tests, the stress intensity factor value was calculated from the value of the breaking load. During equilibrium tests, the stress intensity factor value was determined from the complete equilibrium deformation diagram, taking into account the energy indicators of destruction. The test used nanofiber-reinforced concrete, in which carbon nanotubes are used as crack propagation inhibitors at the level of the cementing agent, and various macro-sized fibers are used at the level of fine-grained concrete. As a result of the tests, it was found that the methods for determining the recovery factor from cubes with a notch and from deformation diagrams showed a good degree of convergence. Fiber reinforcement affects the fracture toughness of a nanocement composite, and high-modulus fiber has a greater effect on fracture toughness than low-modulus fiber. The stress intensity factor is a good indicator for comparing different types of fiber reinforcement in terms of their effect on fracture toughness

Technological project of the existing plants reconstruction of large-panel housing construction: problems and solutions

Increasing the volume of construction and meeting the requirements to reduce the cost of housing contribute to the flourishing of industrial housing. First, industrial housing is cheaper, and its construction is necessary for implementation of the state policy in relation to the needy in improvement of housing conditions of needy disabled citizens, and also their other categories enjoying the privileges provided by the legislation (social housing). Secondly, with the transition to the construction of residential buildings of modernized series, i.e. houses of modern consumer and operational qualities, it is possible to move to meet the needs of a wider range of consumers, namely the more affluent segments of the population, organizations and enterprises of various forms of ownership. Thus, project institutes have developed new standard series of panel buildings, allowing to build housing with increased kitchens, bathrooms, staircases, equipped with freight elevators. In the development of some standard series managed to ensure that modern panel houses have Bay Windows, French balconies, individual architectural solutions, non-standard input groups. Solutions for the development of a series of 25-storey houses, as well as industrial 3-room houses of the manor type for rural areas on the basis of products of large-panel housing (LPH) construction are being worked out. To date, there are 14 enterprises of efficiency and house-building plants in the Republic, of which 8 enterprises are subordinated to the Ministry of construction and architecture of the Republic of Belarus and 6 enterprises are in communal ownership, and all enterprises to a greater or lesser extent require the renewal of technological equipment, reconstruction of industrial buildings and structures. In order to solve this problem, a State comprehensive program for the development of the material and technical base of the construction industry was developed, within the framework of which investment projects for the reconstruction, modernization and technical re-equipment of LPH plants were implemented

New technical solutions for construction of the Minsk ring highway

In Byelorussia the network of highways intensively develops. For their construction and reconstruction modern technologies are used. The sample of new technical decisions in road construction can be counted the Minsk ring highway. Questions of erection of an earthen cloth on bogs have been here successfully solved. Geosynthetic materials, blacktop with cellulose fibres, noise protection screens from profile metal are used. Construction of bridges and overpasses was carried out with wide application of preliminary intense bearing designs. The bridge cloth and sidewalks are executed from monolithic concrete. For strengthening slopes, ridge vibropressing plates are applied. All works were carried out by wide front with maximal use of highâ€efficiency road technics. With the purpose of management of a condition roadway parts on the Minsk belt line three road measuring stations are constructed. They allow to carry out works under the account of transport streams and influences of meteorologicalâ€climatic factors on the trafficâ€operational condition of a highway. First Published Online: 21 Oct 201

Electrical conductivity of cement mortar with the addition of graphene

With the development of technological innovations in the field of construction, increasing the efficiency of energy-saving materials used, more and more attention is paid to electrically conductive materials. Electrical conductivity studies were carried out on samples of concrete with graphene addition to obtain the current–voltage characteristics of the material. In order to identify the mechanism of the effects of different concentrations of graphene on electrical conductivity, a series of samples with different concentrations of graphene was made. As a result of the research, it was found that the dependence: the resistivity of the materialthe concentration is percolation, the concentration of graphene in the amount of 8% of the mass of cement is the percolation threshold

Nanoindentation of cement stone samples

The preliminary results of the studied cement samples were obtained by the nanoindentation method. It was revealed that the elastic modulus M increases in samples that contain a complex additive containing nanosized particles. The effect is also observed with the introduction of an additive containing only one type of nanoparticles (nanosilica sol SiO2 or carbon nanomaterial MCNT). The selection of the parameters of the nanoindentation method, which ensured the obtaining of the final consistent results, was performed. These results are presented by histograms of the distribution of nanoindentation points in modulus of elasticity M and hardness H and distributions in M and H in the horizontal XY plane perpendicular to the motion of the nanoindentor. The results obtained indicate that there is a change in the nanostructure of the C – S – H gel, which is compared with an increase in strength, Young’s moduli and shear, upon the introduction of SiO2 nanoparticles and MCNT nanoparticles

Pile quality assessment by vibroacoustic method

In recent years, there has been a steady growth in industrial and civil construction, especially in large cities. Construction is often carried out in increasingly difficult geotechnical and hydrogeological conditions. This contributes to the emergence of new production technologies and diagnostic methods. The use of non-destructive testing methods allows you to quickly obtain information about various characteristics of an object without disrupting the process of its operation. This is especially true for hidden work, since access to the research object is practically closed, and its opening may entail undesirable consequences for the operation of the entire structure

Fracture toughness of carbon nanotubes modified cement based materials

С. А. Жданок, Е. Н. Полонина, Е. А. Садовская, С. Н. Леонович. ВЯЗКОСТЬ РАЗРУШЕНИЯ ЦЕМЕНТНЫХ МАТЕРИАЛОВ, МОДИФИЦИРОВАННЫХ УГЛЕРОДНЫМИ НАНОТРУБКАМИIn order to increase the fracture toughness of concrete, dispersed fiber reinforcement is increasingly used in practice. The initiation of crack initiation occurs at the nanoscale in the cement matrix. Thus, the use of nano-reinforcement with dispersed nanoparticles can have a positive effect on the fracture toughness of the cement composite. It is proposed to consider carbon nanotubes (CNTs) as such nanofibers. This article discusses the possibility of using nanocarbon tubes as elements for restraining the development of cracks at the nanoscale in cement composite. The results of testing nanomodified cement stone for strength indicators, fracture toughness indicators, results of nanoindentation, ultrasonic sounding and infrared spectroscopy are presented. A structural model of a cement stone dispersed-reinforced with nanocarbon tubes is considered

The Hypervisors of Safety using Technology of Hardware Virtualization

In the article the approach to construction of system of protection of the information from unapproved access on the basis of program safety hypervisor for the hardware architecture which are not supporting technology of the hardware virtual machine is considered. The model of protection on the basis of traditional safety hypervisor for the systems supporting the hardware-software virtual machine is considered, and attempt of displaying of the given model on a case of absence of support of the specified technology is made

Effect of calcium sulfoaluminate additive on linear deformation at different humidity and strength of cement mortars

The effect of calcium Sulfoaluminate additives (CSA) on the compression and bending strength of mortar, as well as linear deformation of prism samples at different environmental humidity was studied. Test results indicate that bending strength of mortars with CSA and the referent at the age of 28 days are practically equal. Compressive strength of mortars with CSA reduced by 20 ... 23% for all dosages of CSA. Relative linear deformations depend on the humidity of the environment. At a humidity of 100%, the relative linear deformations are positive and the expansion increases with increasing dosage of the expanding additive. When hardening in dry air at a humidity of 55%, the greatest shrinkage deformations were observed for mortars with CSA. We can conclude that the expanding effect of CSA is fully manifested at high humidity, i.e. under construction conditions, this means very high-quality moisture care for concrete structures

Effect of calcium sulfoaluminate additive on linear deformation at different humidity and strength of cement mortars

The effect of calcium sulfoaluminate additives (CSA) on the compression and bending strength of mortar, as well as linear deformation of prism samples at different environmental humidity was studied. Test results indicate that bending strength of mortars with CSA and the referent at the age of 28 days are practically equal. Compressive strength of mortars with CSA reduced by 20 ... 23% for all dosages of CSA. Relative linear deformations depend on the humidity of the environment. At a humidity of 100%, the relative linear deformations are positive and the expansion increases with increasing dosage of the expanding additive. When hardening in dry air at a humidity of 55%, the greatest shrinkage deformations were for mortars with CSA. We can conclude that the expanding effect of CSA is fully manifested at high humidity, i.e. under construction conditions, this means very high-quality moisture care for concrete structures