Papers by Keyword: Frost-Resistance

Abstract: In this paper, influence of new plasticizers on the mechanical and low-temperature properties of rubbers is studied. The subjects of the research are rubbers based on BNKS-18 butadiene-nitrile rubber and Hydrin T-6000 epichlorohydrin rubber (ECHR). As used plasticizers: DINP (diisononylphthalate), TOTM (trioctyltrimellitate), DOA (dioctyladipate), Alphaplast (complex plasticizer based on esters of organic alcohols and acids). For identification the efficiency, rubbers with the studied plasticizers compared with standard rubber, in which plasticizers have not introduced, as well as with rubber in which a widely used industrial plasticizer DOF (dioktilphthalate) was added. Research of the mechanical properties of rubbers based on BNKS-18 showed that the introduction of plasticizers leads to an increase in elasticity and a slight decrease in the strength of rubbers and on the contrary for rubbers based on ECHR. Low-temperature properties of rubbers with all studied plasticizers have an increased level in comparison with standard rubber. In rubber based on BNKS-18, the highest values of the coefficient of frost resistance at-45°C are observed with the introduction of plasticizers Alphaplast and DOA, an increase in the index compared to standard rubber is more than 50%. The same plasticizers have shown the greatest contribution to the increase in frost resistance of rubbers based on ECHR.

Abstract: The results of development of frost-resistant rubber based on epichlorohydrin rubber (ECHR) of Hydrin T6000 brand of Zeon Chemicals L.P. (USA) are described in the present work. The properties of ECHRs are determined by the nature of the structural units that constitute the macromolecules. The absence of olefinic functionality in the main chain gives ECHR the resistance to heat, oxygen, ozone and other factors. The presence of chlorine causes the high resistance of Hydrin T6000 rubber to the effect of hydrocarbon media (oils, fuels, fats, waxes, solvents), and the presence of oxygen atoms helps to maintain the flexibility and elasticity of materials at low temperatures. Hydrin T6000 rubber has the lowest glass transition temperature (T_gt = -60 ° C) from all the epichlorohydrin rubber brands, high oil resistance, increased heat and ozone resistance, and, therefore, attracts researchers' interest as a promising rubber for the development of frost-resistant rubber with sealing capability. The paper presents the formulation of rubbers based on Hydrin T6000 and the results of studies of their physical and mechanical properties. Analysis of the data revealed that the obtained rubber has excellent frost resistance, increased oil resistance at a satisfactory level of residual deformation after compression and strength characteristics. Thus, Hydrin T6000 has established itself as a promising rubber for manufacturing frost-resistant rubber with sealing function and will provide increased reliability and durability of equipment operation in extreme conditions of cold climate in Russia.

Abstract: The article presents experimental data on the improvement of physical and mechanical properties and structure of fine-grained concrete by mechanical activation of sticky cement in various apparatuses. It is established that the use of mechanoactivation technologies allows controlling the surface characteristics of cement in a wide range, its granulometric composition, as well as the physical and mechanical characteristics of concrete products. It is revealed that the efficiency of grinding machines that realize various mechanisms of disperse action is not the same. The highest indexes belong to the concrete containing cement, which is mechanically activated on the planetary ball mill AGO-2.

Abstract: The connection with the icing on the frost resistance of concrete containing slag cement and chemical additives «MC Bauchemie» under freezing and thawing.It is shown that freeze concrete samples at (-) 10°C increase in the amount of slag from 30 to 70 wt.% Of binder in the composition leads to an increase in the index of ice formation in the concrete of 1.7 ... 1.9 times compared with the concrete obtained at a slag containing slag cement with a content of 10 wt.%. Frost resistance of concrete is reduce from F450 to F400.When freezing of concrete samples at (-) 20°C increase in the amount of slag from 30 to 50 wt. % Binder in the composition leads to an increase in the index of ice formation in the concrete of 1.7 times compared with the concrete obtained on slag cement containing slag with a content of 10 wt.%. Frost resistance of concrete is reduce from F400 to F350.The concrete on the slag containing cement with slag 70 wt. % is observed a slight decrease in ice formation. However, its value is 1.4 times higher than ice formation in concretes containing slag in an amount of 10 wt. %. Mark on frost resistance remains at F350.The smallest ice formation, regardless of the content of the slag into the slag containing cement, concrete characterized in that use complex organo-mineral supplement SX (5%) + SP (0.6%) in the amount of 5.6%. According to the degree of influence of additives used to reduce ice formation in the slag in concretes, containing cements can be ranker number: SX (5%) + SP (0.6%) > NC (5%) + SP (0.6%) > SP (0.6%).

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: Using the fast freeze-thaw test method, we tested the loss modulus and compressive strength of steel slag-limestone powder concrete after 0,25 times,50 times,75 times,100 times freeze-thaw cycle,studied the mechanical properties and frost resistance performance after the freeze-thaw cycle. The results showed that adding a certain amount of steel slag-limestone powder does not affect the anti-frost property of concrete; established different dosage of steel slag concrete freeze-thaw damage model: y = a + bx + cx2, degree of fitting is better; large quantity of steel slag used in concrete shall be a wider range of research.

Abstract: With the study of frost resistance of plain concrete and mixed concrete with fly-ash substituted and mixed concrete with fly-ash substituted and nanoSiO₂ as admixture, the outcomes of the test go that the frost resistance of concrete with nanoSiO₂ will be increased considerably.

Abstract: Influence of aggregate types on the impermeability and frost-resistance of concrete with different water/cement ratios were investigated, as well as the pore structure and hydrates of the ITZ. The results show that, concrete prepared with a high water/cement ratio and using granite aggregate, presents the highest values of chloride diffusion coefficient and the lowest numbers of freeze-thaw cycles. Whereas concrete prepared with a low water/cement ratio and using limestone aggregate, obtains the similar durability results. The limestone aggregate with a rough surface and higher water absorption, has a tight bonding with the cement paste. However, the granite and basalt aggregate that formed by magma eruption, have higher activity. The XRD results demonstrate that more clinkers participate in the hydration of cement, therefore, resulting in a denser ITZ. In order to improve the concrete durability, the basalt aggregate both with higher activity and rough surface is consider optimal.

Abstract: The influence of admixture on concrete pore structure was analyzed by using the mercury intrusion method and the rapid frozen-thaw method under the condition of the same water/binder ratio in this paper, and thus the relationship between pore structure and frost resistance of concrete were analyzed. When the compound mineral ad-mixture is mixed, the porosity rate of concrete can be decreased and the harmful hole is in-creased, the less-harm hole and the no-harmful hole are decreased. The early strength of concrete is not decreased. But the strength has the increasing trend in the late, which is more favorable for the impermeability and corrosion resistance. But the improvement of the freezing resistance is not obvious. The admixture of air entraining agent can increase the porosity and more-harmful hole, and the concrete strength will be decreased, which will be not favorable for the freezing resistance of concrete. If these two substances are admixed at the same time, the concrete porosity is increased, and the pore size distribution of concrete can be reasonable. The decrement of concrete strength is not obvious, but it is favorable for the freezing resistance of concrete.

Abstract: A study was made into the resistance in frost-thaw cycles and chloride penetration of silica-fume concrete by simulating the characteristics of the marine environment and using the R-value evaluation method. The results show that as a result of mixing silica fume in concrete, the R-value increases by 52.1%; the composite use of silica fume and air-entraining agent with an adequate mixing amount can increase substantially the comprehensive property of concrete in resisting frost-thaw cycles and chloride penetration, with the magnitude of R-value increase being as high as 174%~ 284% and the silica mixing amount being best at around 10%.