strength

Concrete is the most widely used building material due to its versatility, durability and availability of raw materials. With the development of the construction industry requirements to concrete, in particular their strength, are increased. Increasing of the physical and mechanical properties and crack resistance of cementitious composites during the operation of buildings and structures is an actual problem in engineering practice. A special class of fiber reinforced materials – engineered cementitious composites (ECC) has been developed for this purpose.

In the article the analysis of literary sources concerning methods of gypsum binders modification is shown. It is shown that today more and more attention is paid on the ecology of production and the maximum efficiency of the use of natural resources, therefore the development of non-klinker binders, such as anhydrite and gypsum, is relevant.

Exposure to elevated temperatures has detrimental effects on the properties of concretes based on the Portland cement, leading to irreversible changes, up to total failure. One of solutions to improve resistance of structures after exposure to high temperatures may be the use of cement-based materials modified at the nanoscale.

The modified concrete mixes design and cement concrete with the given operational parameters was developed. During the experiment, cement concrete was obtained from concrete mixtures of various compositions with modifying additives of a new generation containing a superplasticizer based on polycarboxylates and an air-absorbent additive. Superplasticizer was injected into a concrete mix with water in a quantity of 0,6; 0,8 and 1,0 % of the mass of cement, and the additive-aeration – in the amount of 0,1 % of the mass of cement in all the components of concrete.

The application of engineering cementitious composites (ECC) – a specially developed class of cement-based material reinforced with fibers – allows to enhance the loading capacity, stability under static and dynamic influences, as well as durability of building structures due to controlled cracking process. The design of engineering cementitious composites is based on the concept of micromechanics, which includes the strength and energy criteria of deformation strengthening throughout the wide range from the macro- to the nanostructural level.

Every construction is influenced by different factors during operation. As a result, there are various defects and damage of these elements, which affects their operating condition. One of such defects is the corrosion of the working rebar. Investigation of samples with corrosion is a complicated and labor-intensive process. Instead of corrosive effects, we perform controlled valves of damaged. In this way, we obtained experimental samples with a fixed value of reducing the diameter of the valve.

In many countries (Japan, USA, China, Poland, etc.) the studies of the influence of laser radiation on the surface of various building materials are being carried out for a long time, including the military purposes. Most attention has been paid to the interaction of laser radiation with the surface of metals.

The relationship between spalling formation on model wheels tread surface and cyclic fracture toughness of steels with nitride strengthening is study. It is shown that the nitride strengthening of wheel steels has a positive influence on damage resistance of surface rolling of model wheels. To improve the serviceability of wheel steels with nitride strengthening indicated the need to optimize their chemical composition providing content of carbon in the range of 0.50...0.55 %, vanadium — 0.08...0.12 % and nitrogen — 0,008...0,015 %.

The results of studies of the impact strength, temperature factors and parameters of cutting tool geometry on the formation of the stress-strain and thermodynamic state of surfaces with different types of engineering materials in the cutting process are described in the article. Analysis of simulation modeling of power, temperature and deformation parameters is the basis for making of forecasting models of influence of the structure and process parameters on the formation of complex operational properties of the product.