Influence of constant magnetic field on the properties of waste phosphogypsum and fly ash composites

Construction and Building Materials 89 (2015) 13–24

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Influence of constant magnetic field on the properties of waste phosphogypsum and fly ash composites Marek Zielin´ski ⇑ Laboratory of Environmental Threats, Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, University of Lodz, Tamka Street 12, 91-403 Lodz, Poland

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 Constant magnetic field as an

additional parameter in the creation of composites.  Composites from waste.  Thermal treatment of waste phosphogypsum.

a r t i c l e

i n f o

Article history: Received 23 August 2013 Received in revised form 6 March 2015 Accepted 12 April 2015

Keywords: Constant magnetic field Building materials Composites Phosphogypsum Fly ash

a b s t r a c t The paper presents a study of the effect of constant magnetic field on composites used in building industry. The effect of changes was obtained both by direct exposure of the samples to CMF and by using magnetically treated mixing water. Particularly good results were obtained in flexural strength test for (gypsum–phosphogypsum) composite, in which that parameter increased by 30% (from 2.35 to 3.07 MPa), as well as for (cement–fly ash–phosphogypsum) one, in which it increased by 150% (from 2.39 to 6.11 MPa). In compression strength test, that parameter for (cement–fly ash–phosphogypsum) composite improved by 110% (from 7.09 to 14.98 MPa). Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction The aim of the paper was to present the potential applications of CMF (constant magnetic field) for improvement of the physical properties of some building materials and composites and to consider the possible mechanisms of the effect of CMF on materials. It was demonstrated by direct exposure of material samples to CMF in an electromagnet and by using magnetically treated water. Waste materials of phosphogypsum and fly ash type were the additional components of the composites besides the basic ones such as cement and gypsum. Phosphogypsum (PG) is one of the materials ⇑ Tel.: +48 (42) 6355782/6355788; fax: +48 (42) 6355796. E-mail addresses: [email protected], [email protected] http://dx.doi.org/10.1016/j.conbuildmat.2015.04.029 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved.

used in the presented study. It is a by-product of chemical industry, consisting mainly of calcium sulphate, formed in the process of phosphoric acid production [1]. PG waste may be applied as a mineralize in Portland cement clinker burning [2–7] and as an additive which, like natural gypsum, regulates the setting properties of cement [8–13]. The second material investigated in such studies are fly ashes (FA). They are obtained as waste in power plants where pulverised coal and brown coal is burnt. The researchers have been interested for a long time in the effect of magnetic fields on chemical processes. Although the energy of magnetic interactions is low, under specific conditions even weak magnetic fields may cause perceptible changes in the rate of chemical processes [14]. It was observed in the study that CMF affects stable rates of chemical reactions. CMF influences not only chemical and electrochemical

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reactions, but also the crystalline structure, physical and chemical properties of the final products [15–19]. A team of scientists headed by Gehr et al. [20], investigated SO2 ions present in a solution, 4 which was then placed in CMF of magnetic induction B = 4.75 T. The results indicated that CMF contributes to favourable gypsum properties with respect to its density and disintegration. The effect of CMF on atoms manifests itself as stresses in the crystalline network, whereas in a liquid magnetic fields acting both on electrons and on ionized atoms cause dynamic effects [21–23]. In the study by Mwaba et al. [24] the effect of magnetic field with 0.1 T induction on crystallization of CaSO4 was investigated. The authors observed formation of crystals with larger surface area, acceleration of their formation, as well as one specific direction of growth of these crystals. Iwai et al. concluded in their study [25] that the magnetic field has a number of useful functions, such as, among others, the magnetic anisotropy phenomenon, or generation of Lorentz force. Beaugnon et al. [26] observed that the magnetic field, both homogeneous and inhomogeneous, exerts a certain force on the materials and can be used for modification of their physical properties. Water molecules present in the structure of building materials take various forms. Asymmetrical distribution of charges in the water molecule induces a large dipole moment of water. Free electron pairs generate electric forces, which attract the positively charged molecules present in the vicinity. Because of high electronegativity of oxygen, electrons agglomerate closer to the oxygen nuclei than to the hydrogen ones. Thus, the positive charge of hydrogen is emphasized. Protons attract negative charges, also the free pair of electrons of an appropriate another atom. Water contains H3O+ and OH ions, which are susceptible to the effects of both electric and magnetic field. The differences in the physical properties of water are manifested as the changes in the surface tension, viscosity, dielectric permittivity, electrical conductivity. This is the consequence of modification of water structure and molecular dynamics. The structure of water can be changed by electric field, magnetic field, pressure, content of other substances, or temperature. As stated in the paper by Coey and Cass [27], the changes caused by CMF in water persist for up to 200 h. Such changes are dependent on the magnitude of magnetic induction, as observed by Kobe et al. and Higashitani et al. in their studies [28,29]. They also depend, as stated by Backer and Judd, on the direction of magnetic field lines [30], as stated by Higashitani et al. and Tai et al., on the time of exposure to magnetic field [31,32] and, according to Alimi et al., on pH [33]. Higashitani and Oshitani [34] stated that CMF causes changes in the structure of water molecules and ions contained in water, as well as hydrated ions adsorbed on the surface of colloidal particles. The study presented in this paper involved the development of cement-gypsum composites utilizing waste PG and FA. CMF was also used for magnetic processing of mixing water and initial seasoning of the produced samples (standardised trabecular samples). First, their properties such as radioactivity, humidity and chemical compositions were investigated. Then, the formulations of composites were designed so as to comply with the standards adopted for building materials. The properties of mixing water used for the composites such as density, viscosity, electric conductivity, chemical composition were also determined. Then the samples in the form of standardised trabecular samples were produced and subjected to tests for absorptive properties, frost resistance, mechanical strength when bent, compressed when crushed. 2. Materials and methods 2.1. Materials Components of the composites were such materials as Portland cement (CEM I 42.5 R), manufactured by CEMMAC, 91442 Horne Srnie (Slovakia), compliant with the PN–EN 197–1 (EN 197–1:2000) standard; gypsum marked with symbol CE 06, manufactured by Dolina Nidy, compliant with EN 13279-1-B1/20/2; 1 mm

(099) quartz sand of (0.1–1.2 mm) grain size range, supplied by Kreisel. The composites were obtained using waste materials such as raw PG from ‘‘Police’’ Chemical Plant in Police (Poland) and FA from the Heat and Power Plant in Lodz (EC-2) (Poland). Phosphate ore comes from Morocco. The mean humidity of raw PG obtained from five samples was 57.6%. The chemical composition of raw PG and FA was investigated according to standard analytical determination methods. The results have been presented in Tables 1 and 2. The radioactivity of PG and FA were measured in the Intersector Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 90–924 Lodz (Poland). The measurements were performed using a HPGe Spectrometer cooled with liquid nitrogen with max. 30% efficiency for Pb-210. The samples were dried at 80 °C, then comminuted and weighed. Both sample types were normalised to two types of disc geometry – of 15 g and 50 g weight. The measurement time did not exceed 6 h. The measurement uncertainties were estimated on the basis of 1r and for the selected measurement time. They usually do not exceed 10% of the measured radionuclide activity value. The efficiency curve was plotted using LABSOCS – Genie 2000 software, and calibration was verified against the IAEA 327 – Soil standard. The standard was measured on geometries of 15 and 50 g weight. Two coefficients, f1 and f2, were used for assessment of the quality of building materials. Coefficient f1 informs about body exposure to gamma radiation emitted by radionuclides of geological origin: potassium K-40, radium Ra-226 and thorium Th-228. It has a complex form, taking into account different weights of the particular radioisotopes:

f 1 ¼ 0:000 SK þ 0:0027 SRa þ 0:0043 STh 6 1

ð1Þ

where: SK, SRa, STh – the respective concentrations of potassium K-40, radium Ra-226 and thorium Th-228 in Bq/kg. Coefficient f2 informs about the level of pulmonary epithelium exposure to alpha radiation of radon Rn-222, or its derivatives:

f 2 ¼ SRa 6 185 Bq=kg

ð2Þ

where: SRa – concentration of radium Ra-226 in Bq/kg. The following activities (expressed as the means of two geometries) were measured for FA (Table 3). As it follows from the calculations, coefficient f1 for FA amounted to 0.9461, whereas coefficient f2 was 103.2. Therefore, FA, even in its original form without any admixtures could be used. The following activities (means of two geometries) were measured for raw PG (Table 4). As it follows from the calculations for raw PG, coefficient f1 amounted to 2.483, whereas coefficient f2 was 513.3. The above indicates that PG can be used only as an additive whose content will amount to ca. 1/3 of composite composition by weight. Then, f1 will be equal to 0.8277 and f2 will equal 171.1 [13]. 2.2. Methods 2.2.1. Methods of thermal analysis (TG, DTG, DTA) Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA) methods were used to investigate the polymorphic changes of the main component of PG in processing. A Thermogravimetric Analyser, with drying rate of 10 K/min., was used to obtain the respective derivatograms. Waste PG was processed by heating at 210–230 °C (483–503 K) in t = 0.25 h. On the basis of literature data [35] and own research, the progress of dehydration of CaSO4l2H2O, i.e., the main PG component in the process of heating was determined. The knowledge of processing-induced polymorphic changes of the main PG component is helpful for analysis of further investigation of composites. In theory, dehydration of gypsum dihydrate according to reaction (3):

CaSO4  2H2 O ! a  CaSO4  1=2H2 O þ 3=2H2 O

ð3Þ

is possible from the point of view of thermodynamics from 107 °C (380 K) (Fig. 1).

Table 1 Chemical composition of PG. Components of PG

Content (% by weight)

CaO SO3 P2O5 Fe2O3 SiO2 F Al2O3 H2O crystall. Rare-earth elements Loss on ignition Total pH

31.00 42.83 3.91 0.50 0.13 0.26 0.77 18.60 0.60 1.40 100.00 2.4

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Mixing water electric conductivity values were observed to increase as a result of water processing in CMF of magnetic induction B = 1 T for 30 min.

Table 2 Chemical composition of FA. The components of FA

Content (% by weight)

SiO2 Al2O3 Fe2O3 CaO SO3 Other Loss on ignition Total

52.10 25.90 7.40 2.50 0.50 8.10 3.50 100.00

Decomposition of hemihydrate gypsum to soluble anhydrite according to reaction (4) is possible at the temperature above 207 °C (480 K):

a  CaSO4  1=2H2 O ! a  CaSO4 ðIIIÞ þ 1=2H2 O

ð4Þ

Dehydration reactions have been reported to be endothermic reactions. Then, under experimental conditions, a 67 mg raw PG sample was investigated with thermodynamic analysis methods (TG, DTG, DTA), using a thermogravimetric analyser, in which the drying rate was 10 K/min. A derivatogram presented in Fig. 2 was obtained. At the moment of phase change, the line forms the peaks oriented downwards, which evidences endothermic processes (at temp. 95 and 130 °C). Thermal energy expenditure necessary for polymorphic changes of a 67 mg raw PG sample was calculated and found to amount to 254.5 J/g. As it follows from the derivatogram, the first peak (95 °C) reflects a considerable loss of hygroscopic water mass with the increase of temperature (the baseline PG humidity was 57.6%). The second peak (130 °C) represents transformation of dihydrate gypsum into hemihydrate gypsum according to reaction (3). The temperature shift from the theoretical 107 °C value to 130 °C is due to the presence of impurities like P2O5, F, organic matter and alkali. As it followed from the experiments, a mixture of hemihydrate gypsum, with considerable predominance of the a variant (Fig. 3). 2.2.2. Investigation of mixing water parameters in and outside constant magnetic field The chemical composition of mixing water was determined by means of capillary electrophoresis (EC). An Agilent 7100 capillary electrophoresis system was used to obtain the respective electrophorograms. The content of selected anions:  3 Cl, SO2 4 , NO3 and PO4 was determined in water processed by exposure to CMF of magnetic induction B = 1 T for 30 min and non-processed. The water was processed in CMF both in a glass and in a polypropylene container. The electrophorogram of such waters is presented in Fig. 4.  3 Besides the peaks of Cl, SO2 4 , NO3 and PO4 anions, some impurities in the matrix are also visible. The areas under the peaks were then calculated to obtain the concentrations of the particular anions in water. These numerical values are presented in Fig. 5. As it can be seen from the graph, mixing water processed in CMF contained fewer anions than water which had not been processed magnetically. The dynamic viscosity of mixing water gw was measured with a Ubbelohde viscometer at 25 °C. The time of exposure to CMF of B = 1 T was 5 min. Viscosity of water not exposed to CMF amounted to 0.8942 cP whereas after exposure to CMF it was 0.9046 cP. The change of dynamic viscosity of mixing water gw in CMF changed by Dgw = 1.16%. Water density (qw) was measured with pycnometric method. Density under no exposure to CMF 0.99744 g/cm3 and in CMF 0.99786 g/cm3 was measured. The duration of exposure to CMF of B = 1 T was 30 min. CMF was regarded to induce negligible changes in water density, as the change amounted to 0.04%. The electric conductivity of mixing water was measured with a CC – 505 digital conductometer. Electric conductivity of mixing water was tested for 2 weeks in two series, both on water processed in CMF of magnetic induction B = 1 T for 30 min, and on non-processed water. The results are presented in the form of graphs (Figs. 6 and 7).

2.2.3. Composition and method of formulation of composites The composition and testing of composites was based on the following standards: PN-EN 196-1:2005 (methods of cement testing – determination of mechanical strength), PN-85/B-04500 (building mortars), PN-88/B-04300 (cement). Measurements of PG and FA radioactivity were also included so as to adjust their contents in the composites in compliance with the applicable standards. Phosphogypsum waste, before its application in composites, was subjected to thermal processing at temp. 210–230 °C (483–503 K), for 0.25 h. The purpose of that process was dehydration of PG and obtaining the desirable form of crystalline structure of calcium sulfate, applicable in building materials – reactions (3) and (4). At such temperature, besides the reduction of PG humidity from 57.6% to 2.7%, also the content of soluble phosphate groups was reduced from 1.78% to 0.12% – the boiling temperature of phosphoric acid is 213 °C (486 K). Gokon et al. [36] established that CMF enhanced in aqueous solutions induction of coagulation processes, among others, of phosphates, which would obviously reduce the amount of soluble phosphates. Coey and Cass [27] confirmed in their studies that reduction of the diffusion layer thickness under the influence of CMF (9) facilitated the coagulation process. Certain amount of insoluble phosphates may be reduced [37]. Phosphate ions, known to be incorporated in the structure of calcium sulfate (CaSO4) delay the conversion of its hemihydrate to dihydrate. Phosphate ions undergo dissociation on the surface of CaSO4 crystals. The process of formation of phosphate complex with calcium ions (phosphate precipitation process) is inhibited because of the presence of SO2 4 ions. This facilitates the course of the reaction and the passage of phosphate ions into the solution in the form of phosphoric acid (5):  ½CaðH2 OÞn H3 PO4 þ þ SO2 4 ! ½CaðH2 OÞn SO4  þ H3 PO4

ð5Þ

The effect of CMF favored such a reaction, which was observed in the study by Gabrielli [38]. Thus, owing to the effect of CMF, good conditions for elimination of phosphate ions from the CaSO4 crystal lattice in phosphogypsum were created. The mean content of waste materials used in the composites was 25% by weight for processed PG, 30% by weight of FA and 35% by weight of both PG and FA, if both materials were present in the composite. The formulations of composites conforming to the above assumptions are listed in Table 5. The study of the obtained composites was divided into four parts: The first part (I) involved the use of mixing water not exposed to CMF (B = 0) and seasoning also without exposure to CMF (B = 0) (Fig. 8). The second part (II): involved processing of mixing water in CMF of B = 1 T, for t = 0.5 h, whereas seasoning was associated with no exposure to magnetic field (B = 0). The third part (III): involved no exposure of mixing water to magnetic field (B = 0) whereas seasoning took place in CMF of magnetic induction B = 1 T, for t = 5 h. The fourth part (IV): involved processing of mixing water in CMF of B = 1 T, for t = 0.5 h and seasoning in CMF of magnetic induction B = 1 T, for t = 5 h. From each of these parts, standardised trabecular samples of 10  10  120 mm and 40  40  160 mm dimensions for testing of mechanical strength, absorptive properties and resistance to frost were obtained. The molds firmed with the composite were prepared as follows: small samples were kept in constant magnetic field of induction B = 1 T for 5 h, whereas other small samples as well as big ones were not exposed to the magnetic field. After 24 h, the samples (composites) were taken out of the mould and seasoned for minimum 28 days, at ambient temperature [28 days], and in a drier [500 C, t = 12 h and then at ambient temperature [27.5 days]. 2.2.4. Absorbability of composites The absorbability of composites by weight was investigated as follows. The material samples seasoned for a month were weighed on laboratory scales. Then they were immersed in water for 24 h so that they were completely covered. After 24 h they were taken out, dried on blotting paper at ambient temperature for 0.5 h and weighed (AC). The absorbability of composites (AC) was calculated from the following formula (6):

AC ¼ ðwS  wÞ=w  100%

ð6Þ

where: ws – weight of the trabecular sample saturated with water, w – weight of the dry sample.

Table 3 Activities measured for FA (mean of two geometries). Radionuclides

Activity A (Bq/kg)

Activity DA (Bq/kg)

DA/A (%)

K – 40 Tl – 208 Pb – 210 Pb – 212 Bi – 212 Pb – 214 Bi – 214 Ra – 226 Ac – 228 Th – 234

510 70.9 102.8 75.5 63.2 105.0 87.2 103.2 68.2 123.2

45 6.9 9.5 3.8 5.1 5.8 2.8 9.3 4.4 10.3

8.8 9.7 9.2 5.0 8.1 5.5 3.2 9.0 6.5 8.4

Table 4 Activities measured for raw PG (mean of two geometries). Radionuclides

Activity A (Bq/kg)

Activity DA (Bq/kg)

DA/A (%)

Nb – 95 Pb – 210 Pb – 214 Bi – 214 Ra – 226 Th – 234 K – 40

21.2 963.1 455.2 539.4 513.3 248.3 109.0

2.12 47.3 14.4 12.5 10.2 15.4 4.6

10.0 4.9 3.2 2.3 2.0 6.2 4.2

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20000 15000

Reaction (3)

10000

Δ Z (cal/mol)

5000

Reaction (4)

0 -5000 -10000 -15000 -20000 -25000 -30000 0

100

200

300

400

500

600

700

800

900

Temperature (K) Fig. 1. Correlation of isobaric–isothermic potential DZ with temperature T for gypsum dehydration reaction.

Fig. 2. Derivatogram describing the correlation of changes in PG sample weight and weight differential with temperature changes.

2.2.5. Frost resistance of composites Resistance to frost was assessed with a direct method, which involved alternating freezing of the samples saturated with water at 25 °C for 4 h and then thawing in water at ambient temperature for at least 4 h (within one cycle, and there were 6 such cycles). Frost resistance (FR) was indicated by the finding of weight loss after the samples were dried to regain their constant mass. The weight loss was calculated according to the following Eq. (7):

F R ¼ ðw1  w2 Þ=w1  100%

ð7Þ

where: w1 – sample weight before the measurement, w2 – dried sample weight after the measurement. 2.2.6. Tests of mechanical strength of the composites The tests of mechanical strength of composite samples were performed in the Department of Materials Mechanics of the Technical University of Lodz (Poland). They were performed on a Zwick BT1-FR050TH, A1K testing machine for static compression and elongation tests, serial number 156859 with the following parameters: maximum load 50 kN, equipped with a KAP-TC type force transducer 50 kN (AST Dresden) no 156860/5289, bending test rate 50 N/s, compression test rate 10 mm/min and elongation test rate 50 N/s.

Fig. 3. A SEM image of processed PG used for composite recipes.

2.2.7. Application of constant magnetic field Magnetic treatment of mixing water and initial seasoning of the standardised trabecular samples under CMF conditions was conducted in an ER-2525 laboratory electromagnet manufactured in the Experimental Department of the Polish Academy of Sciences in Poznan. The processes were conducted at magnetic induction level B = 1 T, for time t = 0.5 h for magnetic water processing and t = 5 h for initial seasoning of the standardised trabecular samples of 10  10  120 mm dimensions.

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Fig. 4. Electrophorogram for selected anions of water processed and non-processed by exposure to CMF, in a glass container and in a polypropylene container.

Cl -

SO4 2-

NO3 -

PO4 3-

30

24,54

23,71

25

c (mg/l)

20

15

13,52

12,63

10

7,52 4,5

4,3

5,0

5

0 B=0

B=1 T

Fig. 5. Content of selected anions in mixing water kept in CMF of induction B = 1 T for 30 min and not exposed to CMF.

3. Results and discussion 3.1. Absorbability of composites With respect to absorbability of the tested samples, as a result of exposure to CMF their weight changed by 11% for pure components (cement, gypsum) and by 5–11% for composites (Table 6). The material most susceptible to CMF was gypsum, but only in its pure form. The best composites with respect to CMF treatment were recipes 6 (cement–FA) and 10 (cement–FA–PG), with no CMF treatment recipes 1 (cement–PG), 6 and 10. The heating temperature of 50 °C, had an unfavourable effect on absorbability, both for pure components and for composites, also those exposed to CMF. 3.2. Frost resistance of composites As far as the frost resistance of the tested samples is concerned, CMF processing caused a weight change of 5–8% for homogeneous materials (cement, gypsum) and of 2–12% for composites (Table 7).

Cement was a material more susceptible to CMF. The best composites for CMF processing include recipes 1 (cement–PG), 6 (cement–FA) and 10 (cement–FA–PG), for no CMF processing – recipes 6 and 10. The heating temperature of 50 °C exerted a favourable effect on frost resistance, both for homogeneous materials and for composites. 3.3. Mechanical strength parameters of the composites Mechanical strength of the composite samples was tested in the Department of Materials Mechanics at the Technical University of Lodz. The standardised trabecular composite samples 40  40  160 mm were tested for seasoning without CMF, and for mixing water both processed in CMF and unprocessed (part I and part II). The results are presented in Table 8. The experiment involving seasoning the standardised trabecular composite samples directly between the poles of an electromagnet under constant magnetic field (CMF) (part III and part IV) was possible only for samples of 10  10  120 mm dimensions,

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16 14

Conductivity (μS/cm)

12

B=1T

10 8

B=0 6 4 2 0 0

2

4

6

8

10

12

14

Days (-) Fig. 6. The average measurement from three electric conductivity tests carried out on mixing water processed in CMF and non-processed (series I).

20 18 16

Conductivity (μS/cm)

14 12

B=1T 10 8

B=0

6 4 2 0 0

2

4

6

8

10

12

14

Days (-) Fig. 7. The average measurement from three electric conductivity tests carried out on mixing water processed in CMF and non-processed (series II).

Table 5 Recipes of composites and proportions by weight of the particular components, where: Cp – Portland cement, G – gypsum, S – quartz sand, PG – phosphogypsum, FA – fly ash, Ca(OH)2 – calcium hydroxide, W – water. Recipe number

Components

Proportions by weight

1 2 3 4 5 6 7 8 9 10

Cp:PG:Ca(OH)2:W Cp:W G:W Cp:S:W Cp:PG:W Cp:FA:W G:PG:Ca(OH)2:W G:FA:W Cp:G:S:W Cp:PG:Ca(OH)2:FA:W

3:1.4:0.14:2 3:1 1.4:1 3:6:1.5 3:1.4:2 3:1.5:1.5 1.4:1.4:0.14:2 1.4:1.5:1.5 3:1.4:6:2.5 3:1.4:0.14:1.5:2.5

because the distance between the electromagnet pole pieces was 30 mm. The results are presented in Table 9. With respect to flexural strength of the tested samples, CMF processing caused a change for homogeneous materials (cement by 15–30%, gypsum by 20–65%) and by 4–155% for composites. The best composites for CMF processing included recipes 7

(gypsum–PG), 10 (cement–FA–PG), and 6 (cement–FA). As far as the compressive strength of the tested samples is concerned, CMF processing caused its increase for homogeneous materials (cement by 15–20%, gypsum by 40–60%) and for composites (by 2–110%). The best composite for CMF processing was recipe 10 (cement–FA–PG). As far as brittleness of the tested samples is concerned, CMF processing caused a change of 4–35% for homogeneous materials (cement, gypsum) and of 6–30% for composites. The best composite for CMF processing was recipe 1 (cement–PG). 3.4. Effect of constant magnetic field on curing and structure of composites There is no uniform mechanism of the effect of CMF on water or building materials during the hardening process. A certain complex mechanism is only indirectly indicated by some phenomena. On the basis of literature and own research, it can be concluded that under CMF the physical properties of water and the crystalline structure of the hardening material change. The effect of external CMF on the atoms themselves manifests itself as stresses in the

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Fig. 8. Four variants of the tests.

Table 6 Absorptivity of the composites in the form of standardized trabecular samples 10  10  120 mm, where: part (I) – batched water at B = 0, seasoning at B = 0; part (II) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 0; part (III) – batched water at B = 0, seasoning at B = 1 T (t = 5 h); part (IV) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 1 T (t = 5 h). Recipe number

Seasoning temperature ( °C)

1

T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50

2 3 4 5 6 7 8 9 10

Absorptivity of composites (%) I

II

III

IV

23.1 25.7 15.0 17.1 39.4 39.0 9.6 10.3 21.3 24.7 20.3 21.2 32.9 32.1 33.5 32.6 16.3 17.6 23.7 27.0

22.1 27.9 12.6 13.5 32.0 35.1 8.1 9.1 25.1 27.2 18.8 20.3 39.9 46.0 36.7 37.2 13.8 14.7 21.7 22.4

33.3 27.3 23.8 19.0 43.4 36.2 10.2 7.9 30.6 32.6 15.1 21.2 31.0 38.7 31.8 31.0 15.5 15.1 31.5 33.4

26.9 32.2 15.0 16.3 33.7 33.6 8.9 8.7 29.0 26.6 18.5 22.1 34.2 34.0 34.7 31.4 13.5 14.4 26.4 26.9

Table 7 Frost resistance of standardized trabecular composite samples (10  10  120) mm, where: part (I) – batched water at B = 0, seasoning at B = 0; part (II) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 0; part (III) – batched water at B = 0, seasoning at B = 1 T (t = 5 h); part (IV) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 1 T (t = 5 h). Recipe number

Seasoning temperature ( °C)

1

T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50

2 3 4 5 6 7 8 9 10

Frost resistance of composites (%) I

II

III

IV

11.4 9.9 7.7 6.3 17.1 16.9 2.6 2.4 12.2 10.0 5.8 4.6 17.5 16.8 10.2 10.4 4.6 3.9 7.7 5.2

8.7 6.8 7.5 7.1 16.0 15.9 2.8 2.4 9.7 8.5 5.4 4.3 11.0 6.9 8.7 9.0 4.9 4.2 8.2 7.9

11.1 0 0 4.8 21.1 22.7 1.5 1.2 8.5 7.1 2.9 0.2 23.0 17.1 11.1 11.7 3.9 3.2 3.3 1.0

4.8 4.5 3.4 3.4 17.9 19.0 1.3 1.3 7.2 6.8 1.5 1.0 18.2 17.4 14.8 14.9 4.2 3.9 4.6 5.1

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Table 8 Average mechanical strength and brittleness of standardized trabecular composite samples 40  40  160 mm, where: part (I) – batched water at B = 0, seasoning at B = 0; part (II) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 0. Recipe number

Seasoning temperature ( °C)

Flexural (rf)

1 2 3 4 5 6 7 8 9 10

T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50

Brittleness (–) rt/

Average mechanical strength (MPa) Tensile (rt)

Compressive (rc)

rc < 0.125

I

II

I

II

I

II

I

II

5.08 3.35 7.57 7.59 1.85 2.00 6.05 5.03 5.68 3.47 5.69 5.10 2.35 2.23 1.82 1.75 2.34 1.93 2.39 1.79

2.81 2.08 6.47 7.55 2.57 2.54 5.87 3.95 3.10 2.08 4.09 5.18 3.07 2.59 1.74 1.47 3.88 3.13 6.11 5.88

1.89 1.04 3.36 3.34 0.40 0.39 2.23 1.92 2.00 1.15 2.68 2.40 0.66 0.62 0.43 0.40 0.82 0.55 0.80 0.61

0.81 0.72 3.56 3.93 0.66 0.69 2.64 2.01 1.06 0.63 2.90 2.53 0.73 0.76 0.39 0.36 1.33 1.24 1.87 2.16

15.26 10.22 41.07 31.64 3.89 4.13 21.60 16.91 15.77 9.36 27.61 25.96 5.73 6.13 4.53 4.00 5.64 4.47 7.09 5.43

9.72 6.51 31.80 29.38 6.16 7.57 22.04 17.03 11.02 5.64 25.89 19.59 5.60 6.50 3.88 2.74 9.11 8.24 14.98 17.33

0.124 0.102 0.082 0.106 0.103 0.094 0.103 0.114 0.127 0.123 0.097 0.092 0.115 0.101 0.095 0.100 0.145 0.123 0.113 0.112

0.083 0.111 0.112 0.134 0.107 0.091 0.120 0.118 0.096 0.112 0.112 0.129 0.130 0.117 0.101 0.131 0.146 0.150 0.125 0.125

Table 9 Average flexural and compressive strength of standardized trabecular composite samples 10  10  120 mm, where: part (I) – batched water at B = 0, seasoning at B = 0; part (II) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 0; part (III) – batched water at B = 0, seasoning at B = 1 T (t = 5 h); part (IV) – batched water at B = 1 T (t = 0.5 h), seasoning at B = 1 T (t = 5 h). Recipe number

Seasoning temperature ( °C)

Average mechanical strength (MPa) Flexural (rf)

1 2 3 4 5 6 7 8 9 10

T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50 T = 20 T = 50

Compressive (rc)

I

II

III

IV

I

II

III

IV

1.70 1.90 10.55 8.70 2.75 2.50 3.00 – 1.55 1.45 4.65 4.80 1.90 2.45 2.07 1.77 1.40 – 0.80 0.70

1.65 1.55 7.20 8.55 4.55 4.55 2.65 3.10 1.60 1.65 6.75 5.60 3.30 3.75 2.10 2.20 – 2.70 2.85 1.85

1.53 1.37 9.05 8.50 2.15 2.45 3.70 4.25 1.65 1.30 8.05 4.95 2.00 1.60 2.10 2.30 2.20 2.50 0.90 –

1.65 – 8.90 6.90 2.00 2.70 4.80 4.60 1.35 1.90 6.50 5.50 2.35 1.90 1.80 2.60 2.40 1.65 1.20 1.20

5.65 3.95 22.00 18.45 4.40 3.50 6.60 – 5.20 3.60 13.05 11.09 5.10 4.05 3.47 2.83 2.57 – 2.25 2.00

3.75 4.00 18.65 16.10 6.00 5.35 5.10 5.75 4.55 3.35 13.50 13.60 6.35 7.00 3.45 2.75 – 4.35 7.00 6.75

2.80 3.07 18.30 17.10 2.30 2.80 6.85 6.00 3.20 1.40 13.05 11.75 2.70 1.80 3.35 3.50 3.00 3.55 1.20 0.37

3.35 1.15 18.30 23.50 2.45 3.25 9.50 11.00 3.90 4.40 11.55 11.30 3.25 2.85 2.50 3.85 3.75 2.95 2.60 2.20

crystalline structure. In contrast, magnetic fields in liquids, acting both on electrons and on ionized atoms, cause dynamic effects. The movement of masses causes, in turn, modification of the fields. Thus, we have a complex coupled system of matter and fields [21]. The curing process of building material mass involves an interaction between the liquid and the solid phase. As established by Costa et al. [39], the interactions between the material grains may be as follows: capillary ones (attracting forces), Van der Waals ones (attracting forces), Coulomb electrostatic forces in the double layer (repelling forces), expansive pressure (repelling forces) as well as hydrodynamic interaction. If the particles are small (106–102 mm)(colloidal particles), electrostatic Coulomb forces and Van der Waals forces predominate, whereas in the case of larger particles (0.1–1 mm) capillary forces become

predominant. Hydrodynamic forces, which are of low significance in the absence of CMF, become more important under exposure to CMF. Due to its effect, magnetohydrodynamic forces Fm are generated in the solution. They can be defined by Lorentz formula (8) [40–42]:

F m ¼ Q  ðU  BÞ

ð8Þ

where: Q – molecule charge, U – molecule velocity vector, B – magnetic induction vector. CMF induces in the molecules, predominantly diamagnetic, specific magnetic dipole moments, the value of which is proportional to magnetic field intensity H [22,23] and, therefore, also to magnetic induction B. The magnetic dipole moments are induced in diamagnetic substance molecules in the direction opposite to

´ ski / Construction and Building Materials 89 (2015) 13–24 M. Zielin

the direction of CMF induction. The above considerations confirm the information included in another publication [43], demonstrating that atoms and molecules exposed to CMF are subjected to mechanical forces. The occurrence of these forces and their effects are dependent on magnetic properties of the substance exposed to CMF. An important feature of diamagnetic atoms and molecules is that their magnetic moments under no exposure to CMF equal zero. This is due to mutual compensation of the magnetic moments generated by a pair of electrons moving on their orbits in opposite directions. The magnetic induction B vector lines in a diamagnetic substance are less dense, whereas they are more dense outside the substance (Fig. 9). It means that CMF reduces the distance between diamagnetic molecules. Thus, the situation is that diamagnetic dipoles under CMF are both oriented (in the direction opposite to the B vector) and arranged to form an orderly system. Non-compensated charges present on the surface of the forming crystals of the material originate from non-saturated valences of superficial atoms. Such non-compensated charges on the phase surface attract the ions from the solution, thus creating a double electrical layer at the interface of both phases. One layer – Stern layer, is composed of ions bound rigidly to the surface with the opposite charge (it provides a stabilizing charge of colloidal particles). The other one – Gouy diffusion layer – is composed of dispersed ions (with weaker bonds and a tendency towards diffusion into the solution) [23]. The diffusion layer is a determinant of the whole double layer thickness. Using the classic double layer model for composite masses may arouse some doubts as their surfaces do not demonstrate thermodynamic equilibrium, but it is an approximate solution. Reduction of the double layer thickness facilitates coagulation. It also causes a change in surface charge and concentration of the electrolyte. Exposure to CMF is a factor that reduces the thickness of Nernst diffusion layer (dD) (Fig. 10) near the surface of the solid phase [28,32,50], which can be described by the following Eq. (9):

dD  1:59ðqRv 2=3 D1=3 Þ

1=3

ðnFCBÞ1=3

ð9Þ

where: q – liquid phase density, R – radius of the solid phase area, m – liquid phase kinematic viscosity, D – ion diffusion coefficient, n – number of electrons involved in the reaction, F –Faraday’s constant,

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C – concentration of molecules in the liquid phase, B – magnetic induction. Reduction of Nernst diffusion layer (dD) thickness resulted in increased concentration of molecules (C) at the solid phase, with consequent deposition of a large amount of molecules according to the following Eq. (10):

m  0:63ðqRÞ1=3 v 2=9 D8=9 ðnFCBÞ1=3

ð10Þ

where: m – mass of the molecules. Lorentz magnetic forces induced movement of the liquid phase, tangent to the surface of the liquid phase and perpendicular to the direction of magnetic induction B. The liquid phase flow was presumed to be laminar and unidirectional. Navier – Stokes hydrodynamic layer (dH) was formed, thus causing reduction of the diffusion zone (dD) [15,19]. After some transformations, the velocity of molecules in the liquid phase exposed to CMF can be calculated from the following Eq. (11):

U  ðnFCDBPr1=3 g1 dH Þ=0:62  ðnFCD4=3 Bq1=3 dH Þ=ð0:62g4=3 Þ

ð11Þ

where: g – dynamic viscosity of the liquid phase, Pr ¼ D=v ¼ ðDqÞ=g (Prandtl number). On the basis of Eq. (11) it can be established that molecular velocity (U) increases with an increase of magnetic induction (B). An increase of B results also in increasing thickness of Navier– Stokes hydrodynamic layer (dH), which determines the liquid phase flow under exposure to CMF. The electrokinetic potential f, which is the measure of electrostatic interactions between the molecules has been observed to change under exposure to CMF [44–46]. There were uncompensated charges, originating from unsaturated valences of surface atoms, which were present on the surface of forming crystals of the building materials. Uncompensated charges on the surface of the solid phase attracted ions from the solution and a double electrical layer was created at the interface of the two phases. One of the layers was composed of ions bound rigidly to the surface with the opposite sign. It was the Stern layer forming a stabilizing charge of colloidal particles. The second layer, called a diffusion (Gouya) layer, consisted of diffuse ions, forming weaker bonds, tending to diffuse into the solution. As the distance from the Stern layer increased, the zeta potential f decreased

Fig. 9. Induction of magnetic moments (l) in diamagnetic materials (composites) under exposure to CMF and a decrease of vector B (magnetic induction) lines density in the diamagnetic and increase of their density outside the diamagnetic – orientation and reduction of intermolecular distances.

´ ski / Construction and Building Materials 89 (2015) 13–24 M. Zielin

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Fig. 10. Reduction of the diffusion layer (dD) thickness and formation of a new hydrodynamic layer (dH) in the liquid as a result of acting magnetic forces (Fm) generated in CMF – increased coagulation of molecules, where: dR – Stern rigid layer, dD – Nernst diffusion layer, dH –Navier–Stokes hydrodynamic layer, Uo – molecular velocity near the solid phase, U – molecular movement velocity in the solution, Csph – concentration of the solution near the solid phase, C – concentration in the bulk solution, B – magnetic induction, Fm – Lorentz magnetic force.

exponentially. Under the influence of CMF, the diffusion layer decreased (9), while the velocity of the particles increased (11). As it follows from Smoluchowski formula (12) [35]:

n¼

4p U g Ee

ð12Þ

where: U – velocity of the particles, g – dynamic viscosity of the liquid phase, E – electric field intensity, e – relative permittivity of the liquid phase.It caused the electrokinetic potential f to increase again. It should be noted that it is the increase in the value of f in the negative direction, which is associated with a negative charge of particles surface. The pH value also increased then, which was beneficial for building materials.

Fig. 12. Increase of water hydrogen bonds potency in CMF and orientation of water dipoles in line with vector B, where: H – hydrogen, O – oxygen, E+, E – positive and negative electrostatic potentials, B – magnetic induction, l – resultant magnetic dipole moment.

The samples were seasoned in CMF at magnetic induction B = 1 T. Fig. 11 presents photographs of SEM images of (cement– PG–FA) composites (recipe 10) mixed either with mixing water processed in CMF of magnetic induction B = 1 T, or not exposed to CMF. CMF enhanced the strength of hydrogen bonds and arranged the structure of water in an orderly manner (Fig. 12). Water dipoles were arranged along the lines of the magnetic field. The above changes resulted in a different course of composite hydration and curing of the materials. The material structure was finer but more resistant to bending and compression (recipe 10, Tables 8 and 9). As it follows from the literature data, the level of cement hydration increased under exposure to CMF. As explained by Higashitani et al. [47], under the influence of CMF the ion hydration shell became thicker and more difficult to be removed. Water molecules underwent ordering. This can be explained as follows. The

Fig. 11. Photographs of SEM images of (cement–PG–FA) composites (recipe 10) mixed either with mixing water processed in CMF of magnetic induction B = 1 T, or not exposed to CMF, at 20 °C, scale 4 lm.

´ ski / Construction and Building Materials 89 (2015) 13–24 M. Zielin

arrangement of charges in the water molecules was asymmetrical. This caused the polarity of the water molecules that became dipolar in nature (dipole moment of the water molecule is 6.13  103 cm). In the electric dipole, which was located in the external magnetic field appeared, a magnetic dipole moment lind appeared, induced because water is a diamagnetic, and has no permanent magnetic moment. The induced magnetic dipole moments lind oriented the water molecules in the direction opposite to the magnetic induction vector B of the external magnetic field. Oriented water molecules forming the hydration shell of ions, proceeded faster together with them towards a chemical reaction. Hydration of gypsum, phosphogypsum, cement or composite while hardening involved the cations (+) being surrounded by water molecules so that the oxygen atoms were as close to the cations as possible. In contrast, when water molecules surrounded the anions (–), hydrogen atoms were located nearest to the anions. Under CMF conditions, paramagnetic atoms and ions were oriented according to the magnetic induction vector B, and diamagnetic ones in the direction opposite to vector B. Therefore, the hydration reaction might be affected with an increase of hydration heat (negative value of hydration enthalpy) of the individual components. Dissolution enthalpy (DHdis) is the sum of hydration enthalpy (DHhydr) and lattice energy Ulatt (passing of the ion from the salt lattice to the solution by transition to gaseous state, requiring the supply of energy equal to the lattice energy). An increase of hydration enthalpy (DHhydr) of the individual components in composite hardening process under CMF conditions causes a parallel increase of dissolution enthalpy (DHdis). As these reactions were exothermic, it caused an increase in the reaction temperature and, at a further stage, an increase in the mechanical strength of the material after hardening.

4. Conclusions The aim of the paper was to present the potential applications of CMF (Constant Magnetic Field) for improvement of the physical properties of some building materials and composites and to consider the possible mechanisms of the effect of CMF on materials. The experiments carried out in the CMF environment confirmed its effect on the physical and strength-related parameters of the selected cement–gypsum composites produced on the basis of waste PG and FA. The effect of CMF of induction B = 1 T was varied. It was determined by the type of parameter, kind of composite and the way in which the effect of CMF was exerted. The effect of CMF was exerted either by using magnetically treated water (w) or by direct exposure of the samples to CMF (c). With respect to absorbability, it was reduced by 5% for the (cement–FA) composite (c) and by 2% for the (cement–FA–PG) composite (w). With respect to resistance to frost, it was increased by 3% for the (cement–PG) composite (w), by 3% for the (cement–FA) composite (c) and by 5% for the (cement–FA–PG) composite (c). With respect to mechanical flexural strength, it increased for the (gypsum–PG) composite by 30% (w) and for the (cement–FA–PG) composite by 150% (w). With respect to mechanical compressive strength, it increased by 110% for the (cement–FA–PG) composite (w). With respect to brittleness, there was a 33% increase for the (cement–PG) composite (w). Utilization of waste materials is recommended both in view of depletion of natural resources and in consideration of environment protection. It must be, obviously, associated with the demand of the market and economic profitability. Acknowledgment This work was supported by the Lodz University.

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References [1] Pérez-López R, Álvarez-Valero AM, Nieto JM. Changes in mobility of toxic elements during the production of phosphoric acid in the fertilizer industry of Huelva (SW Spain) and environmental impact of phosphogypsum wastes. J Hazard Mater 2007;148:745–50. [2] Karagoz A, Ozturk O, Oguz H. Utilisation of phosphogypsum and oil shale as raw materials for cement clinker production. Appropriate Environmental and Solid waste Management Technologies for Developing Countries. Turkey: 2002. p. 381–8. [3] Ballim Y, Graham PC. Early-age heat evolution of clinker cements in relation to microstructure and composition: implications for temperature development in large concrete elements. Cem Concr Compos 2004;26(5):417–26. [4] Akın AI, Yesim S. Utilization of weathered phosphogypsum as set retarder in Portland cement. Cem Concr Res 2004;34(4):677–80. [5] Kacimi L, Simon-Masseron A, Ghomari A, Derriche Z. Reduction of clinkerization temperature by using phosphogypsum. J Hazard Mater 2006; 137(1):129–37. [6] Mun KJ, Hyoung WK, Lee CW, So SY, Soh YS. Basic properties of nonsintering cement using phosphogypsum and waste lime as activator. Constr Build Mater 2007;21(6):1342–50. [7] Taher MA. Influence of thermally treated phosphogypsum on the properties of Portland slag cement. Resour Conserv Recycling 2007;52(1):28–38. [8] Ghosh SN. Advances in Cement Technology. New Delhi, India: Tech Books International; 2002. [9] Bentur A. Effect of gypsum on the hydration and strength of C3S pastes. J Am Ceram Soc 1976;59:210. [10] Degirmenci N. Utilisation of phosphogypsum as raw and calcined material in manufacturing of building products. Constr Build Mater 2008;22:1857–62. [11] Degirmenci N. The using of waste phosphogypsum and natural gypsum in adobe stabilization. Constr Build Mater 2008;22:1220–4. [12] Zielin´ski M. Utilization of phosphogypsum in the aspect of environmental protection. Przem Chem 2006;7(85):478–83. [13] Zielin´ski M. The use of industrial waste, aided by constant magnetic field, for stabilization of the road’s surface subsoil. Przem Chem 2013;8(92):1453. [14] Kipriyanov AA, Purtov PA. Bull Korean Chem Soc 2012;33(3):1009. [15] Zielin´ski M, Mie˛kos´ E. Influence of constant magnetic field on the electrodeposition of Co–Mo–W alloys. J Appl Electrochem 2008; 38(12):1771–8. [16] Szmaja W, Kozłowski W, Polan´ski K, Balcerski J, Cichomski M, Grobelny J, et al. Study of the morphological and magnetic structures of nanocrystalline cobalt films obtained by electrodeposition. Mat Chem Phys 2012;132(2–3):1060–4. [17] Szmaja W, Kozłowski W, Polan´ski K, Balcerski J, Cichomski M, Grobelny J, et al. Investigation of thick cobalt films electrodeposited on gold substrates. Chem Phys Lett 2012;542:117–22. [18] Zielin´ski M. Effects of constant magnetic field on the electrodeposition reactions and cobalt–tungsten alloy structure. Mat Chem Phys 2013; 141(1):370–7. [19] Zielin´ski M. Influence of constant magnetic field on the electrodeposition of cobalt and cobalt alloys. Int J Electrochem Sci 2013;8(11):12192–204. [20] Gehr R, Zhai ZA, Finch JA, Rao SR. Reduction of soluble mineral concentrations in CaSO4 saturated water using a magnetic field. Water Res 1995;3(29):933. [21] Jackson JD. Classical Electrodynamics. Warszawa, Poland: PWN; 1987. [22] Orchard AF. Magnetochemistry. USA: Oxford University Press; 2007. 176. [23] Griffiths DJ. Introduction to Electrodynamics. New Jersey 07458, USA: Prentice Hall, Inc., Upper Saddle Rider; 1999. [24] Mwaba MG, Gu J, Golriz MR. Effect of magnetic field on calcium sulfate crystal morphology. J Crystal Growth 2007;303(2):381–6. [25] Iwai K, Akiyama J, Sung MG, Furuhashi I, Asai S. Application of a strong magnetic field on materials fabrication and experimental simulation. Sci Tech Adv Mater 2006;7(4):365–8. [26] Beaugnon E, Bourgault D, Braithwaite D, Rango P, Perrier de la Bathie R, Sulpice A, Tournier R. Material processing in high static magnetic field A review of an experimental study on levitation, phase separation, convection and texturation. J Phys I France 1993;3(2). [27] Coey JMD, Cass S. J Magn Magn Mat 2000;209:71. [28] Kobe S, Drazˇic´ G, McGuiness PJ, Meden T, Sarantopoulou E, Kollia Z, et al. Mater Sci Eng, C 2003;23:811. [29] Higashitani K, Iseri H, Okuhara K, Kage A, Hatade S. J Colloid Interface Sci 1995;172:383. [30] Backer JS, Judd SJ. Water Res 1996;30:247. [31] Higashitani K, Kage A, Katamura S, Imai K, Hatade S. J Colloid Interface Sci 1993;156:90. [32] Tai CY, Wu C-K, Chang M-C. Chem Eng Science 2008;63:5606. [33] Alimi F, Tlili MM, Gabrielli C, Georges M, Ben Amor M. Water Res 2006;40:1941. [34] Higashitani K, Oshitani J. J Colloid Interface Sci 1998;204:363. [35] Kurdowski W. The Chemistry of Cement and Concrete. Kraków, Poland: Cement Poland; Warszawa, Poland: PWN; 2010. [36] Gokon N, Shimada A, Kaneko H. J Magn Magn Mat 2002;238:47–55. [37] Madsen HEL. J Crystal Growth 1995;152:94. [38] Gabrielli C et al. Water Res 2001;35:3249. [39] Costa V, Massazza F. 8th JCCC. Rio de Janeiro 6, Brasil; 1986, p. 248. [40] Lioubashevski O, Katz E, Willner J. Magnetic field effects on electrochemical processes: a theoretical hydrodynamic model. J Phys Chem B 2004;108:5778.

24

´ ski / Construction and Building Materials 89 (2015) 13–24 M. Zielin

[41] Bund A, Kohler S, Kuhnlein HH, Plieth W. Magnetic field effects in electrochemical reactions. Electrochim Acta 2003;49:147. [42] Tabakovic I, Riemer S, Sun M, Vas’ko V, Kief M. Effect of magnetic field on electrode reactions and properties of electrodeposited NiFe films. J Electrochem Soc 2005;152(12):C851–60.

[43] [44] [45] [46] [47]

Plouns MA. Applied Electromagnetics. New York, USA: Mc Graw-Hill; 1978. Chibowski E, Hołysz L, Szczes´ A. Colloids Surf A 2003;222:41. Hołysz L, Chibowski E, Szczes´ A. Water Res 2003;37:3351. Chibowski E, Szczes´ A, Hołysz L. Langmuir 2005;21:8114. Higashitani K, Oshitani J, Ohmura N. Colloids Surf A 1996;109:167.