Phase Transformations in Cement Matrix at Low Temperatures

2020 ◽  
Vol 992 ◽  
pp. 86-91
Author(s):  
Ekaterina Potapova ◽  
I. Korchunov ◽  
S. Perepelitsyna
Keyword(s):  
Phase Composition ◽  
Phase Transformations ◽  
Low Temperatures ◽  
Frost Resistance ◽  
Cement Matrix ◽  
Polymer Additives ◽  
Composition And Structure ◽  
Average Size ◽  
Positive Effect ◽  
Helium Pycnometry

The paper presents the results of the phase composition and structure of cement, hardened under alternating freezing/thawing. The fluctuation in the density of the cement through the number of freezing/thawing cycles was determined by the method of helium pycnometry. It is shown that the average size of micropores changes in the presence of plasticizing additives. It is determined that the type and size of pores in the cement effect on frost resistance. The positive effect of mineral slag on the frost resistance of the binder is demonstrated. The positive effect of mineral and polymer additives on the frost resistance of the binder has been discovered and presented in this work.

scholarly journals Increasing the frost resistance of ‘Golden Delicious’, ‘Gala’ and ‘Šampion’ apple cultivars

2016 ◽  
Vol 28 (2) ◽  
pp. 125-135 ◽  
Author(s):  
Grzegorz P. Łysiak ◽  
Robert Kurlus ◽  
Anna Michalska
Keyword(s):  
Low Temperatures ◽  
Frost Resistance ◽  
Foliar Application ◽  
Frost Damage ◽  
Positive Influence ◽  
Field Application ◽  
Positive Effects ◽  
Golden Delicious ◽  
Apple Cultivars ◽  
Positive Effect

Abstract The aim of this research was the evaluation of whether the application of 5-ALA, which has potential as a plant growth stimulating agent with indirect anti-stress activity, can limit the damage caused by low temperatures in winter. The research was conducted on frost-sensitive apple cultivars for three years in an orchard and in a laboratory. During the vegetative seasons of each year, the trees of three apple cultivars (‘Golden Delicious’, ‘Gala’ and ‘Šampion’) were subject to 5-ALA foliar application. Three times during each winter following the field application, apple shoots were taken to the laboratory and frozen at −20°C, −25°C and −30°C. After incubation, the damage to the sensitive parts of the shoots was evaluated. The application had a positive effect on the frost resistance of all cultivars, most often at the end of dormancy, which is especially noteworthy because frost damage occurs most frequently during this period. Positive effects of the application were found in most of the experiment combinations of cultivar, year, freezing date and shoot part. Additionally, the positive influence of 5-ALA application on frost resistance was found to increase with each year of the research.

Effect of phase composition and structure of maraging steel 00Kh11N10M2T on its susceptibility to embrittlement when aged at low temperatures

1981 ◽  
Vol 23 (9) ◽  
pp. 659-663
Author(s):  
S. S. Ryzhak ◽  
L. V. Tarasenko ◽  
I. P. Zhegina ◽  
V. I. Titov ◽  
V. P. Grebennikova
Keyword(s):  
Phase Composition ◽  
Maraging Steel ◽  
Low Temperatures ◽  
Composition And Structure

Features of radiothermoluminescence of polypropylene and ethylene propylenediene elastomer SKEPT-4044 compositions with nanoscale metal-containing fillers

2020 ◽  
pp. 66-73
Author(s):  
A.M. Magerramov ◽  
◽  
N.I. Kurbanova ◽  
M.N. Bayramov ◽  
N.A. Alimirzoyeva ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Molecular Mobility ◽  
Fe3o4 Nanoparticles ◽  
Low Temperatures ◽  
Frost Resistance ◽  
Relaxation Processes ◽  
Ethylene Propylene ◽  
Temperature Range ◽  
Β Relaxation

Using radiothermoluminescence (RTL), the molecular mobility features in the temperature range of 77-300 K were studied for the polypropylene (PP)/ethylene propylene diene elastomer SKEPT-4044 with NiO, Cu2O and Fe3O4 nanoparticles (NPs) based on ABS-acrylonitrile butadiene or SCS-divinyl styrene matrices. It has been shown that the introduction of nanofillers in PP significantly affects the nature and temperature of γ- and β-relaxation processes, while the region of manifestation of the β-process noticeably shifts to the region of low temperatures. Composites with Cu2O NPs have a higher β-transition temperature Tβ than composites with other NPs. It was found that PP/SKEPT-4044 composites with Cu2O NPs with a dispersion of 11-15 nm and acrylonitrile butadiene thermoplastics have optimal frost resistance compared to other compositions.

scholarly journals INFLUENCE OF METAKAOLIN ON PROPERTIES OF CONCRETE MODIFIED WITH POLYCARBOXYLATE ADMIXTURE FOR RIGID PAVEMENT REPAIR

2021 ◽  
pp. 90-97
Author(s):  
V.O. Kryzhanovskiy ◽  
◽  
S.O. Kroviakov ◽  
M.V. Zavoloka ◽  
◽  
...  
Keyword(s):  
Abrasion Resistance ◽  
Frost Resistance ◽  
Mineral Admixture ◽  
Rigid Pavement ◽  
Cement Replacement ◽  
Rigid Pavements ◽  
Concrete Mixtures ◽  
Total Shrinkage ◽  
Partial Cement Replacement ◽  
Positive Effect

Abstract. The effect of partial cement replacement with high-activity metakaolin on the strength, frost resistance, shrinkage and abrasion resistance of concrete modified with polycarboxylate admixture MasterGlenium SKY 608. Portland cement CEM II/A-S 42.5 (ПЦ II/А-Ш-500) with partial metakaolin replacement 15 kg (3.75 %) and 30 kg (7.5 %) was used for concrete preparation. The amount of superplasticizer in all studied compositions was 1.2% of cement weight. Slump of concrete mixtures was 6…7 cm. It was found that with increasing amount of metakaolin W/C ratio of mixtures increased slightly. The early compressive and flexural strength (at the age of 2 days) of the composition without metakaolin was higher than similar indicators with partial cement replacement with the active mineral admixture. It is worth noting the positive effect of increasing the metakaolin amount on early strength, because the composition with 30 kg metakaolin had strengths higher at 2 days of in difference to the composition with 15 kg metakaolin. It is necessary to note high frost resistance of all obtained concretes. Its grade of frost resistance reached F200 (evaluated according to the method for road concrete), which is equivalent to the grade F600 for structural concrete. Abrasion resistance was in the low range (0.30-0.31 g/cm2), total shrinkage does not exceed 0.28 mm/m, which in combination with high frost resistance has a positive effect on the durability of concrete mixtures for rigid pavements repair.

scholarly journals Behavior and Energy Losses of Cows during the Period of Low Temperatures

2021 ◽  
Vol 24 (5) ◽  
pp. 46-53
Author(s):  
Oleksandr O. Borshch ◽  
Oleksandr V. Borshch ◽  
Yurii Mashkin ◽  
Vasyl Malina ◽  
Maxim Fedorchenko
Keyword(s):  
Low Temperatures ◽  
Heat Insulation ◽  
Energy Losses ◽  
Strong Wind ◽  
The Past ◽  
Air Temperatures ◽  
The Difference ◽  
And Behavior ◽  
Positive Effect ◽  
Moderate Climate

Over the past 20 years, dairy farms in Ukraine have been actively introducing the keeping of cows in easy-to-assemble premises. However, in a moderate climate (with four distinct year seasons), the issues of microclimate, energy losses of animals and their behavior during the cold period of the year for keeping in such premises have not been fully studied. The purpose of this work was to study the influence of the heat insulation elements use of side curtains in easy-to-assemble premises during the period of low temperatures on microclimate, energy outgoings for thermoregulation and behavior of cows. The research conducted in the central part of Ukraine (Kyiv region). The research was conducted during January-February (29-43 days of the year) 2021. This period characterized by low average daily temperatures of -12.2– -18.7°С, strong wind gusts and daily precipitation in the form of snow. Two easy-toassemble premises for 400 heads were used for research. Parameters of placements (LxWxH): 150х32х10.5 m. The first one was without the use of curtains heat insulation elements, and the second one was with these elements of heat insulation. It was found that the use of polycarbonate wall heat insulation elements had a positive effect on the microclimate in the placement during the period of low temperatures. Indicators of average daily air temperatures in the placement were 3.2 and 8.8°C higher compared to the temperature in the same premise without the use of heat insulation elements and the environment. The wind speed also differed by 0.18 and 11.04 m/s, respectively. In addition, the heat insulation of the walls affected the temperature under the lying cow (+1.8°C), energy outgoings for thermoregulation (-1.93 MJ) and the number of cows that lay in the period of the lowest temperatures (+3.23-9.83%) compared to the placement without heat insulation elements. The difference in temperature of rubber carpet in the compared premises was significant: +3.3°C in the premises with heat insulation elements compared to the premises without heat insulation

scholarly journals Effect of chemical structure and linear density charge of sulfonate-containing aromatic polyamides on interaction with polycations in organic and water-organic media

2019 ◽  
Vol 60 (11) ◽  
pp. 40-47
Author(s):  
Natalya N. Smirnova ◽  
Keyword(s):  
Chemical Structure ◽  
Phase State ◽  
Linear Charge ◽  
Linear Charge Density ◽  
Sodium Sulfonate ◽  
Interpolyelectrolyte Complexes ◽  
Composition And Structure ◽  
Average Size ◽  
Organic Solutions ◽  
Acrylonitrile Copolymers

The interaction of sulfonate-containing aromatic poly- and copolyamides with acrylonitrile copolymers with N,N-dimethyl-N,N-diallylammonium chloride (DMDAAC) and N,N-diethylaminoethylmethacrylate (DEAEM) in organic and water-organic solutions was studied. It was shown that as a result of macromolecular reactions interpolyelectrolyte complexes (IPEC) forms. They are stabilized mainly by electrostatic forces. To characterize the interpolyelectrolyte complexes composition the φ parameter was used, that defines as the ratio of corresponding functional groups molar concentrations of interacting polyelectrolytes. The transformation degree in interpolymer reactions θ was calculated as the ratio of the salt bonds number between polyions to their maximum possible number. It was shown that the main factors determining the composition and structure of forming interpolyelectrolyte complexes are linear charge density of polyelectrolytes, the nature and composition of the solvent in which interpolymer reactions occurs. It is possible to obtain IPEC, the composition of which for the same polycation will vary from φ = 2.5 to φ = 1.0, changing these factors. It was found that at the complexation process is not accompanied by a change in the phase state of the interpolymer system, when the concentration of units with sulfonate groups in the macromolecular polyamide chain 5 mol.%. It was found that the introduction of polycation leads to the formation of IPEC structures in the form of particles with an average size of ~217.7 nm for poly-4,4'-(2-sodium sulfonate) – diphenylaminisophthalamide and ~248.1 nm in the case of poly-4,4'-(2-sodium sulfonate) -diphenylaminterephthalamide. It was shown that the decrease in the polymer content of units with sulfonate groups is accompanied by a decrease in the transformation degree from 0.65-0.66 to 0.18. It was found that the studied complexes can be transferred to the solution by increasing its ionic strength. The result obtained during this work can serve as a base for the development of for the manufacturing technology of film and membrane materials based on sulfonate-containing aromatic poly- and copolyamides.

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