Barbara Pacewska

Warsaw University of Technology, Warszawa, Masovian Voivodeship, Poland

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Publications (37)77.52 Total impact

  • Source
    Wojciech Kubissa, Barbara Pacewska, Iwona Wilińska
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    ABSTRACT: The results of research of mechanical properties and selected other characteristics influencing durability of cement concretes containing cement substitutes were presented. Cement concretes performed with conventional fly ash, fluidised fly ash and their mixture were investigated. The obtained results were compared with findings registered for two types of concrete performed without cement replacements and with cement concrete containing silica fume. The results have shown that cement concrete with redetermined 28-day compressive strength of about 50 MPa and good workability may be obtained using different cement replacements. Generally, these cement concretes exhibited also favorable properties related to concrete durability, i.e. low permeability and sorptivity, and significant reduction of chloride migration coefficient. Favourable results were obtained for cement concrete containing mix of conventional and fluidised fly ashes: good workability, compressive strength after 28th day exceeding 50 MPa, low permeability of water, and low sorptivity, as well as low coefficient of chloride migration. These features were similar as for cement concrete containing silica fume.
    Advanced Materials Research 10/2014; 1054(1):154-161. DOI:10.4028/www.scientific.net/AMR.1054.154
  • Barbara Pacewska, Mariola Nowacka
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    ABSTRACT: This article presents the investigations of the progress of conversion process of calcium aluminate hydrates formed during hydration of calcium aluminate cement at various temperature conditions occurring over time by thermal analysis method. Moreover, the differences of microstructure were also confirmed by SEM/EDS studies and X-ray diffraction analysis. On the basis of the obtained results, it is concluded that thermal analysis method is a very attractive and useful way to identify the structure of hydrated calcium aluminate cement matrix and allows estimating the degree of the conversion at different times of various process conditions. The conversion process of metastable calcium aluminate hydrates into stable hydrogarnet and gibbsite is strictly temperature dependent and could be completed at different times. Acceleration of the conversion is caused not only by the increasing external temperature of storage, but also the temperature inside the sample is very important. The self-heating, which could be strong in large sample, and occurring during first few hours of hydration of calcium aluminate cement, initiates the transformation.
    Journal of Thermal Analysis and Calorimetry 08/2014; 117(2):653-660. DOI:10.1007/s10973-014-3804-5 · 2.21 Impact Factor
  • Iwona Wilińska, Barbara Pacewska
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    ABSTRACT: Binders containing large amounts of cement substitutes have been a subject of interest for many years because of the possibility to reduce the amount of cement in concrete, and in consequence decrease negative influence of cement production on natural environment. In this work, studies related to hydration of binders where 80 % of cement was substituted by blended pozzolana were carried out. The aim of this work was to investigate activation of fly ash–cement system by addition of spent aluminosilicate catalyst, using calorimetry and thermal analysis as main methods of investigations. It was demonstrated that spent fine-grained fluidised catalytic cracking catalyst acts acceleratingly on early hydration of binder. It seems to be beneficial to use up to 10 mass% of this spent catalyst. Higher amounts may cause changes in the mechanism of early hydration. Because Ca(OH)2 in such systems is quickly consumed due to pozzolanic reaction it seems beneficial to modify composition of binders by introducing additional amounts of Ca(OH)2 or cement.
    Journal of Thermal Analysis and Calorimetry 05/2014; 116(2):689-697. DOI:10.1007/s10973-014-3749-8 · 2.21 Impact Factor
  • Barbara Pacewska, Iwona Wilińska
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    ABSTRACT: The aim of this work is to investigate the influence of selected alkaline activators on pozzolanic and hydraulic activities of fly ashes using thermal analysis (TG/DTG) and infrared spectroscopy (FTIR). Two types of fly ashes differing in chemical compositions, especially content of calcium components, were selected for investigations. The study was carried out for two types of samples: (1) fly ash-lime paste performed with low-calcium fly ash and (2) a paste performed with high-calcium fly ash and water without introduction of additional amount of Ca(OH)2. Chemical admixtures NaOH, Na2SO4, and Na2CO3 were added to both the types of samples. It was confirmed that influence of chemical activators on pozzolanic and hydraulic properties of fly ashes strictly depends on the kind of fly ash and availability of Ca(OH)2. For example, in case of high-calcium fly ash, the most active action was exhibited by NaOH solution.
    Journal of Thermal Analysis and Calorimetry 04/2014; 120(1):119-127. DOI:10.1007/s10973-014-4334-x · 2.21 Impact Factor
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    ABSTRACT: The early hydration (up to 24h) of calcium aluminate cement (Al2O3 min. 40%) blended with spent FCC catalyst at two temperatures i.e. 10 degrees C and 25 degrees C was investigated. The calorimetric measurements were used to study cement pastes with constant ratio of water/binder = 0.5 (binder = cement + addition) and containing 0, 5 and 25% mass of mineral waste as replacement part of cement. In addition the kind of created products using X-ray diffraction method was identified. On the basis of obtained results it was found that the influence of spent FCC catalyst on early hydration of calcium aluminate cement strictly depends on temperature of hydration process. At the temperature of 25 degrees C this waste aluminosilicate accelerates setting and hardening of cement, but at the temperature of 10 degrees C acts as retarder. These changes are realized by variation of duration of the induction period and the bigger content of FBCC the bigger the effect is regardless of the temperature of hydration. The presence of this mineral waste causes a minor effect on the crystalline hydrates produced after 1 day of hardening although it clearly increases degree of CA hydration. (C) 2012 The Authors. Published by Elsevier Ltd.
    Procedia Engineering 12/2013; 57:844-850. DOI:10.1016/j.proeng.2013.04.107
  • Source
    Barbara Pacewska, Iwona Wilińska
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    ABSTRACT: Reducing the consumption of cement with simultaneous utilizing waste materials is preferred for reasons of environmental protection. Typical content of materials substituting cement in cement concrete composition does not exceed 35% of mass of binder. More and more interest is aroused to the increase amount of cement supplements above 50%. The mechanism of hydration processes in such complex systems is not fully understood. The aim of this work is to discuss possibilities of using binders with high amount of cement replacements, with particular regard to physical and chemical processes occurring in such systems after addition of water. Based on literature reports and our own research works possibilities of activation of binders containing high amount of cement replacement (e.g. fly ash) were discussed. Further investigations concerning studies on mechanism of physical and chemical processes occurring in such mixtures are needed.
    Procedia Engineering 01/2013; 57:53–62. DOI:10.1016/j.proeng.2013.04.009
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    ABSTRACT: The effect of spent FCC catalyst on early hydration (up to 48 h) of high aluminate cement (Al2O3 >70%) at different ambient temperatures (10, 20, and 30 °C) was investigated. Cement pastes with constant ratio of water/binder = 0.35 (binder = cement + addition) and containing 0, 5, 10, and 15% mass of addition as replacement of cement were studied. The hydration kinetics was determined by calorimetric measurements and the structure of hardened binders after 2 days of curing at an appropriate temperature was also investigated using X-ray, SEM, and thermal analysis methods. Due to the fact that hydration of aluminate cements is highly sensitive to temperature conditions as well as certain changes of temperature are inevitable in practice, the evaluation of the impact of the waste catalyst addition in such conditions is justified. On the basis of obtained results, it was stated that the temperature determines the early hydration of high aluminate cement and decides about the influence of waste aluminosilicate. The introduction of the discussed addition has a big impact on the kinetics of cement hydration closely related to the curing temperature. The presence of spent catalyst accelerates the hydration at the temperatures of 20 and 30 °C, but at the temperature of 10 °C this waste aluminosilicate acts as a retarding agent. The effect of the addition on the microstructure of hardened binders after 48 h of hydration is rather insignificant, especially at 20 °C, compared to the influence of the temperature on hydration. At the temperature of 10 °C, a formation of low amount of C2AH8 can be observed because of the presence of spent catalyst, while at the temperature of 30 °C the introduction of the mineral addition prevents the hydrogarnet formation.
    Journal of Thermal Analysis and Calorimetry 08/2012; 109(2). DOI:10.1007/s10973-012-2233-6 · 2.21 Impact Factor
  • Dariusz Szychowski, Barbara Pacewska
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    ABSTRACT: The purpose of this study was to determine the possibility of producing hydrophobic mesoporous mineral-carbon sorbents from aluminum hydroxide and coal-tar pitch-polymer compositions by carbonization at 600 °C in an nitrogen atmosphere. The method of homogenization was optimized using different solvents. Blends of aluminum hydroxide and coal-tar pitch with a definite composition or the products of co-precipitation of aluminum hydroxide in the coal-tar pitch-polymer medium were subjected to carbonization process. The hydrophilic–hydrophobic properties were evaluated by adsorption of water vapors. The highest value of BET surface area about 370 m2/g, was achieved for the carbonization product obtained from co-precipitated raw components with 10 wt% coal-tar pitch-polymer compositions.
    Journal of Thermal Analysis and Calorimetry 08/2012; 109(2). DOI:10.1007/s10973-012-2341-3 · 2.21 Impact Factor
  • Barbara Pacewska, Dariusz Szychowski
    Journal of Thermal Analysis and Calorimetry 08/2012; 109(2). DOI:10.1007/s10973-012-2564-3 · 2.21 Impact Factor
  • Source
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    ABSTRACT: The purpose of this study was to determine the possibility of producing hydrophobic mesoporous mineral–carbon sorbents from aluminum hydroxide and compositions of coal tar pitch–polymers on carbonization at 600 °C in a nitrogen atmosphere. Blends of the products of co-precipitation of aluminum hydroxide in the carbonaceous substances medium were subjected to carbonization process. The extent of porous structure development was evaluated using low temperature nitrogen adsorption, adsorption of benzene vapors, and adsorption of iodine from aqueous solution. The highest value of BET surface area of about 370 m2/g was achieved for the carbonization product obtained from co-precipitated raw components with 10 wt% compositions coal tar pitch–polymer. These materials demonstrated high capacity to reduce organic pollutions from sewage. Pitch–polymer composition containing poly(ethylene terephthalate) or phenol–formaldehyde resin was studied by the means of DSC method in order to determine the high-temperature transformations taking place under the conditions of carbonization. DSC method enables to determine i.a. the decomposition temperatures of carbonizates produced from pitch–polymer compositions and the evaluation of their sorption abilities. The additive of poly(ethylene terephthalate) and phenol–formaldehyde resin caused the increase of thermal resistance of the pitch expressed by higher decomposition temperatures.
    Journal of Thermal Analysis and Calorimetry 01/2012; 107(3). DOI:10.1007/s10973-010-1257-z · 2.21 Impact Factor
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    Barbara Pacewska, Iwona Wilińska, Mariola Nowacka
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    ABSTRACT: The influence of three mineral additives, i.e. fly ashes from pulverized combustion and from fluidized combustion of hard coal as well as Portland cement, on early hydration (up to 28th day) of calcium aluminate cement was investigated. Cement pastes containing 0, 5 and 25 wt% of additives were studied by the use of calorimetry, thermal analysis and infrared spectroscopy methods. It was confirmed that hydration of calcium aluminate cement is closely dependent on the type of addition and its amount. The influence of additives of different properties on cement hydration was discussed basing on received results and other literature reports.
    Journal of Thermal Analysis and Calorimetry 12/2011; 106(3). DOI:10.1007/s10973-011-1570-1 · 2.21 Impact Factor
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    ABSTRACT: The influence of spent catalyst from catalytic cracking in fluidized bed (FCC) on the hydration of two kinds of calcium aluminate cements (of about 40 and 70% content of alumina) was studied. Cement pastes were prepared with constant ratio of water/binder = 0.5 and with content of 0, 5 and 25% mass of addition as replacement of cement. The samples were stored at room temperature. Thermal analysis (TG, DTG), infrared absorption (FTIR) and X-ray diffraction methods were applied to investigate changes in various periods of hydration (up to 150 days). The compressive strength of cement mortars was also examined. On the basis of presented results it was affirmed that in studied conditions spent FCC catalyst is a reactive addition in calcium aluminate cement (CAC) pastes, which probably can create a new phase type C–A–S–H. It may be an interesting alternative for limitation of the negative phenomenon of conversion of aluminate hydrates, although the degree of the influence of the mineral additive depends on the composition of CAC and of the quantity of the used waste.
    Journal of Thermal Analysis and Calorimetry 07/2011; 105(1):129-140. DOI:10.1007/s10973-011-1303-5 · 2.21 Impact Factor
  • Barbara Pacewska, Iwona Wilińska, Maria Bukowska
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    ABSTRACT: The aim of this work is to compare the influence of addition of waste aluminosilicate catalyst on the initial periods of hydration of different cements, i.e. calcium aluminate cements of different composition and Portland cement, basing on the calorimetric studies. Cement pastes containing up to 25 mass% of additive were studied, where the water/(cement+additive) ratio was 0.5. An attempt was undertaken to explain the mechanism of action of introduced aluminosilicate in the system of hydrating cement, particularly in the case of calcium aluminate cement pastes. It was found that the presence of fine-grained additive caused in all studied cases the increase of the amount of released heat in the first period after the addition of water. In the case of aluminate cements with aluminosilicate addition, a significant reduction of induction time and faster precipitation of hydration products were observed compared to the reference sample (without additive). In the experimental conditions, the additive caused the acceleration of aluminate cements hydration, and the mechanism of its action is probably complex and can encompass: nucleative action of small grains and formation of new chemical compounds.
    Journal of Thermal Analysis and Calorimetry 07/2009; 97(1):61-66. DOI:10.1007/s10973-008-9668-9 · 2.21 Impact Factor
  • B. Pacewska, G. Blonkowski, I. Wilińska
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    ABSTRACT: In this work, the pozzolanic and hydraulic properties of ashes originating from various sources were studied in model systems such as ash and ash-lime pastes. The sources of studied ashes were: fluidized combustion of brown coal, pulverized combustion of brown coal and pulverized combustion of hard coal. This article is a continuation of our previously published studies on cement pastes with mentioned ashes. The following experimental techniques were applied: calorimetry, thermal analysis (TG, DTG) and infrared absorption (IR). Previously drawn conclusions relating to the reactivity of ashes in an environment containing Ca2+ ions were confirmed. According to these conclusions, an ash originating from fluidized combustion of coal exhibited higher reactivity compared to other ashes from pulverized combustion. Pozzolanic and hydraulic properties of this ash were also confirmed. Differences in the behaviour of ashes originating from pulverized combustion of various types of coal in the presence of water and Ca2+ rich environment were demonstrated.
    Journal of Thermal Analysis and Calorimetry 10/2008; 94(2):469-476. DOI:10.1007/s10973-008-9179-8 · 2.21 Impact Factor
  • Barbara Pacewska, Dariusz Szychowski
    Journal of Thermal Analysis and Calorimetry 09/2008; 93(3):669-670. DOI:10.1007/s10973-008-3121-y · 2.21 Impact Factor
  • Barbara Pacewska, D. Szychowski
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    ABSTRACT: The purpose of this study was a preliminary evaluation of mineral-carbon sorbents preparation possibility by the method of thermal decomposition of a mixture of aluminium oxide or hydroxide and acenaphthene and determination of their physicochemical properties. The conditions of carbonization were established and the changes of physicochemical properties of obtained materials as a function of organic substance content in the mineral-carbon mixture before the process of carbonization were tracked. In these investigations the methods of thermal analysis, low-temperature nitrogen adsorption and benzene vapors adsorption were applied.
    Journal of Thermal Analysis and Calorimetry 09/2008; 93(3):763-767. DOI:10.1007/s10973-008-9142-8 · 2.21 Impact Factor
  • Barbara Pacewska, I. Wilińska, G. Blonkowski
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    ABSTRACT: The paper describes an attempt of chemical activation of fly ash and claims the usefulness of combination of such investigation methods as calorimetry and infrared absorption for investigations of early periods of cement hydration. The research samples were cement pastes made with an addition of fly ash and admixtures of chemical activators, CaCl2, Na2SO4 and NaOH, whereas a cement paste without fly ash addition and a cement-fly ash paste (both without admixtures) were used as reference samples. In order to investigate early periods of cement pastes hydration, the amount and rate of heat release were registered, and IR spectrums were checked at appointed hydration moments. As a result, it was shown that the combination of calorimetric and IR absorption methods in the investigations of early periods of cement hydration was useful. It was confirmed that the use of chemical activators CaCl2, Na2SO4 and NaOH accelerated the hydration of cement pastes containing fly ash additive in early hours after adding water. The action of activators on hydrating cement system is different for each of investigated compounds.
    Journal of Thermal Analysis and Calorimetry 09/2008; 93(3):769-776. DOI:10.1007/s10973-008-9143-7 · 2.21 Impact Factor
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    ABSTRACT: Aluminium hydroxide was precipitated during a hydrolysis of aluminium perchlorate in ammonia medium. The materials were studied with the following methods: thermal analysis, IR spectroscopy, X-ray diffraction, low-temperature nitrogen adsorption and adsorption–desorption of benzene vapours. Freshly precipitated boehmite had a high value of SBET=211 m2 g–1 determined from nitrogen adsorption, good sorption capacity for benzene vapours, developed mesoporous structure and hydrophobic character. After prolonged refluxing at elevated temperature its crystallinity increased which was accompanied by an increase of specific surface determined from nitrogen adsorption up to 262m2g–1 , decrease of sorption capacity for benzene vapours and stronger hydrophobic character. The calcinations of all boehmites at temperature up to 1200C resulted in formation of -Al2O3 via transition form of γ-, δ- and θ-Al2O3. The samples of aluminium oxides obtained after calcination at 550 and 900C were characterised with high values of specific surface area of 205–220 and 138–153 m2 g–1 , respectively. The SBET values calculated for the oxide samples derived from aged hydroxides and calcined at 1200C are higher than for the analogous sample prepared without the ageing step. It was concluded that the process of ageing at elevated temperature developed thermal stability of aluminium oxides.
    Journal of Thermal Analysis and Calorimetry 12/2006; 86(3):751-760. DOI:10.1007/s10973-005-7377-1 · 2.21 Impact Factor
  • B. Pacewska, G. Blonkowski, I. Wilińska
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    ABSTRACT: Investigations of physico-chemical properties of three kinds of fly ash and their influence on cement hydration were performed in this work. Thermal analysis, microcalorimetry, infrared absorption and others were used. It was confirmed that the kind of coal and combustion conditions essentially influence physico-chemical properties of fly ash and in consequence influence cement hydration. Investigated fly ashes show in cement system so-called pozzolanic activity. Fly ash from combustion of brown coal in fluidized furnace revealed better activity compared to other investigated ones. This work is an introduction to more extensive investigation of fly ash activation.
    Journal of Thermal Analysis and Calorimetry 08/2006; 86(1):179-186. DOI:10.1007/s10673-005-7136-7 · 2.21 Impact Factor
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    ABSTRACT: An attempt to obtain aluminium hydroxide that could give aluminium oxides of increased thermal stability was made. Aluminium hydroxide was precipitated during a hydrolysis of aluminium chloride in ammonia medium. The influence of preparative conditions, such as a dosing rate of aluminium precursor, pH, duration of the precipitate refluxing and temperature of calcination, on the properties of obtained hydroxides and oxides was investigated. The materials were studied with the following methods: thermal analysis, IR spectroscopy, low-temperature nitrogen adsorption and adsorption–desorption of benzene vapours. Precipitated boehmites had high values of S BET determined from nitrogen adsorption (220–300 m2g–1), good sorption capacity for benzene vapours, developed mesoporous structure and hydrophilic character. It has been proved that a high pH value during the precipitation of aluminium hydroxide favoured better crystallisation of boehmite structure, higher temperature of its dehydroxylation into γ-Al2O3, and delayed transformation of γ phase into α-Al2O3. Aluminium oxides derived from the hydroxides precipitated at a high pH were the most stable at high temperatures, and were characterised with the best surface properties.
    Journal of Thermal Analysis and Calorimetry 01/2006; 85(2):351-359. DOI:10.1007/s10973-005-9987-z · 2.21 Impact Factor

Publication Stats

354 Citations
77.52 Total Impact Points

Institutions

  • 2000–2014
    • Warsaw University of Technology
      • • Faculty of Civil Engineering, Mechanics and Petrochemistry (Plock)
      • • Faculty of Civil Engineering
      Warszawa, Masovian Voivodeship, Poland