Матеріалознавство

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  • Документ
    Complex multifunctional additive for anchoring grout based on alkali-activated portland cement
    (IOP Publishing, 2020) Krivenko, P. V.; Petropavlovskyi, O. M.; Rudenko, I. I.; Konstantynovskyi, O. P.; Kovalchuk, A. V.
    Complex multifunctional additive (further, CA) which consists of aluminum powder, surfactant, salt-electrolyte (NaNO3) and calcium sulfate hemihydrate (CaSO4∙0.5H2O) is proposed for ensuring necessary properties of anchoring grouts based on alkali-activated portland cement (further, AAPC) presented by the system «ordinary portland cement clinker - sodium metasilicate». Specified consistency of fresh AAPC mortar along with it strength after hardening are provided by water reducing due to application of modified polyethylene glycol characterized by stability of molecular structure in AAPC hydration medium. CA influence on shrinkage mitigation in AAPC mortar is explained both water-reducing effect and gas release with volume increasing during formation of dispersive-coagulation structure. Expansion of crystallization-condensation structure is ensured due to stress of calcium hydrosulfoaluminate 3CaO∙Al2O3∙3СаSО4∙32H2O and calcium hydronitroaluminate ЗСаО∙А12О3∙Са(NO3)2∙10Н2О which form due to presence of СаSО4∙0,5H2O and NaNO3 in CA. Time matching of gas release with structure formation insures dense microstructure due to filling of pores by hydrated phases that causes lower excess stress during crystallization. CA ensures necessary performances of AAPC anchoring grout: consistency 190 mm; workability retention time 15 min; tensile strength in bending / compressive strength 6.1 / 25.7 MPа and 12.9 / 68.5 MPa in 1 d and 28 d agreeably; adhesion 0.9 MPa; linear extension up to +0.37 mm/m.
  • Документ
    Development of decisions for alkali-activated cements proper deformations control
    (ПП «Технологічний Центр», 2019-11) Krivenko, P.; Gots, V.; Petropavlovskyi, O.; Rudenko, I.; Konstantynovskyi, O.; Kovalchuk, A.
    The relevance of using cements containing mineral admixtures of both natural and artificial origin is determined by compliance with current trends in sustainable mankind development in terms of efficient consumption of raw materials and energy and responsible attitude to the environment. From the environmental point of view, partial replacement of cement clinker with mineral admixtures contributes to the reduction of CO2 emissions. In addition, materials based on such cements are characterized by high quality, functionality and durability. For example, efficiency of using blast furnace slag, zeolite and limestone in composite eco-cements with high initial strength has been demonstrated [1].
  • Документ
    Development of solutions concerning regulation of proper deformations in alkali-activated cements
    (ПП «Технологічний Центр», 2019-11) Krivenko, P.; Gots, V.; Petropavlovskyi, O.; Rudenko, I.; Konstantynovskyi, O.; Kovalchuk, A.
    The essence of the problem related to proper deformations in alkali-activated cements (AAC) complicated with high content of gel-like hydrate formations was analyzed. Cement types diametrically opposite in their compositions and, accordingly, in the content of gel phases during hydration, that is, the alkali-acti�- vated portland cement (AAPC) and alkali-activated slag cement (AASC) were taken for consideration. Approaches to formation of an effective structure of artificial stone counteracting shrinkage deformation by means of interference in structure formation when using complexes of mineral and organic compounds were proposed. Such compounds in composition of complex organomineral admixtures jointly influence intensification of crystallization processes and formation of an effective pore structure and morphology of hydrate phases while reducing water content in artificial stone. Salt electrolytes of various anionic types and anion-active surface-active substances were considered as ingredients of the proposed complex modifying admixtures. It has been found that the “salt electrolyte–surfactant” system is the most effective for AAPC modification. It was shown that modification of AAPC with this complex admixture based on NaNO3 reduced shrinkage from 0.406 to 0.017 mm/m. Instead, the use of Na2SO4 provided AAC of this type with a capacity of expansion up to 0.062 mm/m. It was shown that the effect of compensated shrinkage of modified AAPC is associated with a higher crystallization of low-basicity hydrosilicates (CSH(B)) and calcium hydroaluminates (CaO∙Al2O3∙10H2O). An additional effect is associated with formation of sulfate-containing sodium-calcium hydroaluminate (for the Na2SO4-based system) and crystalline calcium hydronitroaluminate (for the NaNO3-based system) with a corresponding microstructure stress. For further development, a complex admixture of “Portland cement clinker–salt electrolyte–surfactant” system was proposed for AASC modification. It provided shrinkage reduction from 0.984 mm/m to 0.683 mm/m. Minimization of the modified AASC shrinkage was explained by formation of sodium hydroalumosilicate of gmelinite type ((Na2Ca)∙Al2∙Si4∙O12∙6H2O) with a high degree of crystallization along with low-basicity calcium hydrosilicates. It was noted that the cement stone structure is characterized by high density, uniformity, and consolidation of hydrate formations.
  • Документ
    Alkali activated portland cement with adjustable proper deformations for anchoring application
    (IOP Publishing Ltd, 2019) Krivenko, P. V.; Rudenko, I. I.; Petropavlovskyi, O. M.; Konstantynovskyi, O. P.; Kovalchuk, A. V.
    The application of alkali-activated Portland cement (hereinafter AAPC) for anchoring grouts was investigated with obtaining of non-shrinking high performance cementing systems. The AAPC system “ordinary Portland cement clinker – sodium metasilicate” was modified by the complexes of mineral and organic compounds to ensure specified properties of anchoring grouts. It was revealed that the most effective multifunctional additives are represented by the system “salt-electrolyte – surfactant”. Alongside with slowing down of AAPC paste setting time, the effect of compensated shrinkage of AAPC mortar, i.e. expansion within 0.062 mm/m and slight shrinkage within 0.017 mm/m, was ensured when Na2SO4 and NaNO3 were used in the mentioned system respectively. The effect of compensated shrinkage is explained by greater crystallization of ydrosilicates and hydroaluminates, additional formation of sulfate-containing sodium-calcium hydroaluminate (for Na2SO4-based system) and crystalline calcium hydronitroaluminate (for NaNO3-based system). The advantages of the modified AAPC for anchoring application are indicated in thepaper.
  • Документ
    Вплив органо-мінеральних комплексів на міцність і власні деформації шлаколужних цементів
    (ОДАБА, 2019) Кривенко, П. В.; Петропавловський, О. М.; Руденко, І. І.; Константиновський, О. П.
    Запропоновано комплексну органо-мінеральну добавку складу «портландцементний клінкер – електроліт – поверхнево-активна речовина», використання якої в шлаколужному цементі забезпечує сповільнення строків тужавлення, підвищення показників міцності і практично відсутність усадки (0,062 мм/м). Показано особливості роботи портландцементного клінкеру у лужному середовищі, вплив добавок солей різного аніонного типу та луговміщуючих аніоноактивних ПАР на водопотребу, синтез міцності та власні деформації при гідратації та формування структури штучного каменя на його основі. Відмічена перспективність запровадження таких органо-мінеральних комплексів в якості додаткових компонентів шлаколужних цементів для регулювання їх технологічними і фізико-механічними властивостями, у т.ч. для зменшення усадки цементного каменя
  • Документ
    Enhancement of alkali-activated slag cement concretes crack resistance for mitigation of steel reinforcement corrosion
    (EDP Sciences, 2020-04) Krivenko, Pavlo; Petropavlovskyi, Oleh; Kovalchuk, Oleksandr; Rudenko, Igor; Konstantynovskyi, Oleksandr
    The paper is devoted to mitigation of steel reinforcement corrosion in alkali-activated slag cement (further, AASC) concretes, based on soluble sodium silicates (further, SSS’s), obtained from high consistensy concrete mixes. Enhancement of AASC fine concretes crack resistance due to modification by complex shrinkage-reducing additives (further, SRA’s) based on surfactants and trisodium phosphate Na3PO4.12H2O (further, TSP) was proposed for mitigation of steel reinforcement corrosion. SSS’s were presented by sodium metasilicate (silica modulus 1.0, dry state) and water glass (silica modulus 2.9, density 1400 kg/m3). In case of sodium metasilicate the application of SRA composition “ordinary portland cement clinker – TSP – sodium lignosulphonate – sodium gluconate” provides enhancement of crack resistance starting from early age structure formation with restriction of drying shrinkage from 0,984 to 0,713 mm/m after 80 d. The effect is caused by reduction of water and by higher volume of crystalline hydrates. In turn, SRA presented by compositions “TSP – glycerol” and “TSP – glycerol – polyacrylamide” provide enhancement of AASC fine concretes fracture toughness during late structure formation with increasing ratio of tensile strength in bending to compressive strength up to 37 – 49 % if compare with the reference AASC when water glass is used.
  • Документ
    The efficiency of plasticizing surfactants in alkali-activated cement mortars and concretes
    (EDP Sciences, 2018) Runova, Raisa; Gots, Volodymyr; Rudenko, Igor; Konstantynovskyi, Oleksandr; Lastivka, Oles’
    Functionality of mortar and concrete mixes is regulated by surfactants, which act as plasticizers. The molecular structure of these admixtures can be changed during hydration of alkali-activated cements (AAC). The objective was to determine the chemical nature of plasticizers effective for property modification of mortars and concretes based on AACs with changing content of granulated blast furnace slag from 0 to 100 %. The admixtures without ester links become more effective than polyesters when content of alkaline component increase. The admixtures effective in high alkaline medium were used in dry mixes for anchoring (consistency of mortar 150 mm by Vicat cone; 1 d tensile strength in bending / compressive strength of mortar 6.6 /30.6 MPа) and in readymixed concretes (consistency class changed from S1 to S3, S4 with consistency safety during 60 min; 3 d compressive strength of modified concrete was not less than the reference one without admixtures).
  • Документ
    Fillers for modification of polyester powder coating
    (IOP Publishing Ltd, 2020-09) Gots, V. I.; Lastivka, O. V.; Tomin, O. O.; Tymoshenko, S. A.
    In the article effectiveness of the use of fillers to improve the physical and mechanical properties of the coating varied depending on the average size of the filler particles and crystalline shape was studied. According to the indicators of impact strength to back impact and bending strength of the coating, the most effective is the use of microsilica with an average size of 2.9 μm. As the average filler size increases, the gloss and impact strength of the coating reduce. To increase the bending strength of the coating, it is advisable to use fillers in the form of wollastonite, which is characterized by a fibrous crystal shape, which improves the physical and mechanical properties of the coating and prevents cracking, acting as a reinforcing agent. In addition, the analysis of the obtained study results shows that the use of the studied Ukrainianmade fillers in the powder paint composition promotes obtaining a covering with adjustable physical and mechanical characteristics.
  • Документ
    Influence of whitening additives on the properties of decorative slag-alkaline cements
    (IOP Publishing Ltd, 2020-09) Gots, V. I.; Gelevera, O. G.; Petropavlovsky, O. N.; Rogozina, N. V.; Smeshko, V. V.
    Traditional decorative cements are made on the basis of white cements and the demand for them is constantly growing. But such cements have all the disadvantages of clinker cements, namely, high energy intensity and high price. An alternative may be slag-alkali cements having higher physical and mechanical characteristics and lower price. Therefore, these studies were aimed at choosing such additives that would have the maximum whitening properties and would enhance the stabilization of bleaching processes during hydration and hardening of slag in the presence of alkalis, to determine the simultaneous effect of three additives on the whiteness and physical-mechanical characteristics, as well as to determine the optimal the content of these additives in slag-alkali decorative compositions. In this work, as a result of the studies performed, the possibility of obtaining effective slag-alkali white cements as the basis for the production of decorative concrete with acceptable economic characteristics is proved. The influence of each of the bleaches on such characteristics of decorative slagalkali cements as strength, setting time, whiteness is established. Methods for optimizing compositions are identified.
  • Документ
    Modification of the structure of the stabilized basalt fiber
    (IOP Publishing Ltd, 2020-09) Gots, V. I.; Palchyk, P. P.; Tymoshenko, S. A.; Palchyk, S. P.
    The study of thermophysical, physical-mechanical and acoustic characteristics of coarse continuous basalt fiber in the conditions of influence of operational factors and corrosion environment is carried out. It is shown that obtaining barrier materials with high thermophysical and acoustic properties is possible by creating a porous system in the material with a predetermined textural characteristic of pores of different class, purpose and combination. The influence of the porous system of coarse continuous basalt fiber on the operational properties of flexible heat and sound insulation products and materials has been studied. It is determined that the performance characteristics of flexible thermal insulation materials are in direct proportion to the degree of porosity of the constituent materials and their structural characteristics. Shown that the increase in the operating temperature of these materials, sound and thermal resistance is determined by the chemical and mineralogical composition of the source materials and their structural characteristics. The influence of the mechanism of selective leaching of coarse continuous basalt fibers on their textural characteristics and the zone of operating temperatures is studied.