Applied Mechanics and Materials Vols. 725-726

Abstract: The consideration is given to a specific component of the creep of concrete which becomes apparent within one day from the moment of load application, the so called “short-term creep”. Since the entire creep of concrete is conditioned by its water content, the short-time creep must be assigned to the most mobile water – capillary water. As far as the capillary water behavior is determined by the capillary forces acting in it, the short-term creep of concrete is considered and described in the present work as expression of capillary forces. Such description is based on a modified capillary theory of concrete shrinkage: creep is interpreted as forced shrinkage arising due to the fact that application of load leads to disturbance of hygrometric equilibrium of concrete and environment. In view of the mentioned creep interpretation as the forced shrinkage the isotropic loading of the body is considered. The purpose of this work is to determine the degree in which the capillary forces are source of the short-term creep of concrete.

Abstract:

The purpose of the present work is to research the process of hardening clinkerless slag-alkaline binder materials during the early stage of interaction between the ground granulated blast-furnace slag and the alkaline component by the thermokinetic method. The amount of heat emitted during the interaction between slag and alkaline component, and the influence of the duration of slag pre-hydration period upon this process have been assessed. These values were compared to similar values for binder materials based on portland cement. It was shown that ageing has significantly larger influence on heat emission during hydration of portland cement and on concrete strength.
We have elaborated in more detail the mechanism of hydration reaction of slag-alkaline binder materials starting at the level of active centers on the surface in accordance with the process of self-decelerating forming of crystallization centers. As slag grains are covered with a layer of hydrates, kinetics of hydration till the end of reaction is regulated by the process of diffusion that depends on the degree of structural irregularity.

Abstract: The task of the project is obtaining the dependence between the relative decreasing of strength and rate of strain and substantiation of the new method for determination of concrete frost resistance. It has been analytically proved that using concrete’s rate of strain ε as a measure of damage, instead of decreasing of tensile strength R, increases freeze-thaw resistance’s accuracy of estimation a lot under otherwise equal conditions by the time of freeze-thaw cycling. Also it has been experimentally shown that ratio of relative decreasing R to ε in direction, perpendicular to compression, is assumed to be independent on values R and ε for a given concrete and on the ways of achieving them during mechanical or freeze-thaw cycling. To determine the dependence δR/R by ε (z) 8 specimens were tested by non-destructive method (RU 2 490 631) and two baths of 50 specimens by basic method (thermo cycling). Results of the non-destructive method are different from results by basic method for 6,3%. Dependence of relative decreasing in strength by rate of strain is near to linear and, therefore, value of z is constant. Taking this into account patented methods for estimation of concrete’s freeze-thaw resistance as per values R and ε received after freezing and thawing cycles of some specimens and their postlimenary failure by linear compression was substantiated.

Abstract: In work need of detailed studying of a water phase of a bituminous emulsion about concentration of emulsifier in its structure, and also compatibility with the concrete mineral material used in production is proved. It is offered to bring improvements in a technique of development of a compounding of a bituminous emulsion at a stage of studying and selection of a water phase.

Abstract: In work need of detailed studying of a water phase of a bituminous emulsion about concentration of emulsifier in its structure, and also compatibility with the concrete mineral material used in production is proved. It is offered to bring improvements in a technique of development of a compounding of the bituminous emulsion at a stage of studying and selection of a water phase. Found that in the manufacturer's recommended ranges there is no effective emulsifier concentration having a sinusoidal dependence. Samples of bituminous emulsions prepared using an emulsifier in the range of effective concentrations obtained depending confirmed. As objects of research in work emulsifiers of one of leading producers were used AkzoNobel: RedicoteE-11 и RedicoteEМ-44.

Abstract: Brickwork is one of the most convenient of enclosures. It combines supreme thermal insulation, durability, aesthetic appearance. However, masonry is subjected to plurality of destructive factors, one of which is salt corrosion. Survey of buildings of Saint-Petersburg has been described in this article. Experimental data that proves vulnerability of mortar to salt efflorescence has been obtained. Several solutions of this problem have been recommended and necessity of future researches has been stated.

Abstract: The demand for town houses using the constructions of lightweight conrete is growing rapidly in recent time. One of the most common building materials for cottage construction is lightweight aggregate blocks. An important role for lightweight expanded clay aggregate (LECA) concrete plays such a property as vapor permeability. This paper presents the results of vapor permeability test of the samples, the analysis and recommendations for construction of the building. These samples were taken from the LECA concrete blocks covered by unidentified cladding, of which one of the town houses was under construction in the North-West of Russia. An assumption has been made that the unidentified cladding may cause losses to the building’s wall enclosure.

Abstract: In this paper, we consider the possibility of using, in friction pendulum bearings, multilayer friction proof coatings based on polytetrafluoroethylene compounds modified by nanoscale spinels such as magnesium, zinc and chromium. The tribological effect of applying the coating is achieved by formation of a friction transfer layer. For better wear resistance, we applied a multilayer coating with a power frame covered using electrospark coating. We performed an experimental research of bushing samples and various coating fluoroplastic bases. The research on a friction machine “SMT-1” has shown the effectiveness of epoxy fluoroplastic composition as an anti-friction coating in comparison to other types of fluoropolymer bases.

Abstract: Nowadays, construction often is used a composite material. Including fibro concrete of reinforcing synthetic fibers. In this title was survey the effect of fiber reinforcement. PAN and HC on the properties of concrete in depend of length fibers, its design, types dressing, composition of concrete, aggregate fineness and etc. As a result of influence was revealed that is not depend of length fibers in the same mobility of concrete mix and differente flow consumption of cement concrete strength in compressive decreases and increases a concrete of fiber. The same conditions strength concrete in flexural with increases content fibro rising. In attendance fibro model is deformation decreases but maximum permission increase.

Abstract: The purpose of this work is to show the way that leads to losing of stability of a lattice girder, by gradual becoming plastic of elements. Elements that are allowed to become plastic are inserted into the program SAP2000 as link elements of appropriate characteristics, whereby there is made a numeric modeling of a problem. Finally, the possibility of significant reducing of lattice girder's weight is shown, which has a very favourable economic effect as a consequence