Перегляд Автор "Rudenko, Igor"

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35. The influence of complex additive on strength and proper deformations of alkali-activated slag cements
(Trans Tech Publications Ltd, 2019) Krivenko, Pavel; Petropavlovskyi, Oleh; Rudenko, Igor; Konstantynovskyi, Oleksandr
The peculiarity of alkali-activated slag cements (further, AASC’s) is increased proper deformations, which can cause increased cracking and reduced durability of structure. The paper is devoted to manage AASC’s proper deformations. The main task was to determine the composition of complex additives (further, CA’s) in system «ordinary portland cement (further, OPC) clinker -mineral compound of different anionic type - surfactant» in presence of sodium metasilicate (further, MS) to affect on hydrated AASC performance while ensuring effective structure of artificial stone by criterion of shrinkage deformations. Comparative analysis of hydrated cement systems "OPC clinker - MS", "OPC clinker - mineral compound - MS" and "OPC clinker - mineral compound - MS - surfactant" showed that the greatest effect on reduction of proper deformations occurs when the mineral compounds relate to electrolytes, i.e. Na2SO4 and NaNO3. Hydrated system is characterized by expansion (+0,062 mm/m) in presence of Na2SO4. Almost no shrinkage is supplied by application of NaNO3 (-0,062 mm/m). The obtained CA’s were tested in AASC. CA in the system “OPC clinker - NaNO3 - surfactant” provides the initial setting 43 min, the end - 65 min with accelerated strength. Investigated AASC can be classified as non-shrinking cement. This phenomena is ensured by increasing density, homogeneity and monolithicity of hydrosilicate formations, as well as due to formation of hydroaluminosilicate structures with different morphology by inclusion of nitrate anions.
Effect of technological factors on freeze-thaw resistance of alkali-activated slag cement concrete in NaCl solution
(AIP Publishing, 2023) Krivenko, Pavel; Rudenko, Igor; Konstantynovskyi Oleksandr
The application of alkali-activated slag cement concrete (hereinafter AASC concrete) is relevant for building constructions which are exploited in aggressive environments with exposed class XF4. It is due to increased freeze-thaw resistance of AASC concrete in water solutions of salts if compared with portland cement concrete. The aim of this work was to investigate the effects of technological factors on porous structure and freeze-thaw resistance of plasticized AASC concrete in NaCl solution. It was shown that increasing of fresh concrete consistency from class S1 up to class S4 due to plasticization by complex admixture “polyorganohydrosiloxane - sodium lignosufonate - polyethylene glycol” as well as application of alkaline component in dry form, in contrast to liquid form, ensures negative changes in porous structure of AASC concrete. These changes cause decreasing of freeze-thaw resistance from mark F500 down to F200. It was revealed that hardening of plasticized AASC concrete under normal conditions (t = 20±2 °С, RH = 95±5%), compared with hardening in water or under steam curing (t = 85±5 °С), ensures more effective porous structure which causes maintained freeze-thaw resistance of F300 in contrast to F200 and F250 agreeable. Effective technological decisions for advanced freeze-thaw resistant of AASC concrete were determined.
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.
Enhancement of alkali-activated slag cement concretes crack resistance for mitigation of steel reinforcement corrosion
(EDP Sciences, 2020-04-22) Petropavlovskyi, Oleh; Kovalchuk, Oleksandr; Krivenko, Pavlo; 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 Na3PO .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.
Feasibility of incorporating SO42--ions in zeolite-like matrices based on alkaline aluminosilicate binders
(Elsevier BV, 2023-08) Krivenko, Pavlo; Rudenko, Igor; Konstantynovskyi, Oleksandr; Vaičiukynienė, Danutė
Factors determining minimization of the influence of sulfate environments on concrete and risk of corrosion of embedded steel reinforcement have been analyzed. Coatings based on alkaline aluminosilicate binders were proposed to prevent transport of the sulfate ions into concrete. The formation of water resistant zeolite-like matrices on the alkaline aluminosilicate binder of the Na2O-K2O-Al2O3-SiO2-H2O system at 20 ± 2 ◦C can be provided by the use of calcium-containing modifying additives. Optimized molar ratios between oxides of binder constituent were SiO2/Al2O3 = 4–5 and K2O/(Na2O + K2O) = 0.15–0.30. The results of the study show that the speed of incorporating sulfate ions in cement matrix of binder from the sulfate environment is dependent upon a cation and ranks as follows: (NH4)2SO4 > MgSO4 > Na2SO4 > CaSO4. Complete protection of concrete against the penetration of sulfates can be reached when the developed coating is applied in a thickness of 3 mm.
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).
The efficiency of plasticizing surfactants in alkali-activated cement mortars and concretes
(Transbud-2018, 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).