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8. NMR combined with accelerated weathering 97 B), an expansion of the sample can be observed, i.e., from about 2 µm for fired-clay brick up to 4 µm for Cordova Cream limestone. c , moisture content, [m3m 3] concentration, c [M] expansion, [ m] a) fired-clay brick t [s] c , moisture content, [m3m 3] concentration, c [M] expansion, [ m] b) Indiana limestone t [s]
8. NMR combined with accelerated weathering 98 c , moisture content, [m3m 3] concentration, c [M] expansion, [ m] c) Cordova cream limestone t [s] Fig. 8.4: Measured moisture content, concentration, and expansion as a function of time for a) fired-clay brick, b) Cordova cream limestone, and c) Indiana limestone. Initially all sample are saturated with a 3 M sodium sulfate solution at 40 ◦ C, after which the samples are cooled down to 22 ◦ C and the experiment is started. In order to obtain more information on the salt transport during drying, we have plotted the same data in a so-called efflorescence pathway diagram (EPD) in figure 8.5 [68]. In an EPD, the total amount of sodium sulfate present in the solution, cθ (in mole/kg), is plotted against the moisture content θ. In such a diagram two limiting situations can be distinguished. First, very slow drying, in which case salt transport by diffusion dominates, i.e., P e ≪ 1. In this case, the ion profiles remain homogeneous and for some time no crystallization will occur. The average sodium sulfate concentration will slowly increase until the complete sample has reached the solubility of thenardite (3.4 M). From this point on any additional drying will result in crystallization. Second, very fast drying, i.e., P e ≫ 1. In this case, ions are directly advected with the moisture to the top of the sample, where a concentration peak with a very small width will develop. If the rate of crystallization is high enough, i.e., if there are enough nucleation sites at the top to form crystals, the average Na 2 SO 4 concentration in the solution in the sample itself will remain almost constant at nearly at the initial concentration. Figure 8.5 shows that for all these experiments P e ≪ 1 during the initial drying in the first cycle, indicating that diffusion is dominant. In this case we expect a homogeneous crystallization behavior throughout the sample and the expansion will be representative for the crystallization in the material. We like to note that these EPDs confirm that thenardite is being formed in the samples. When the relative moisture content in the samples has dropped to about 25 %, the
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Sodium sulfate heptahydrate in weat
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To my family
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CONTENTS 1. Introduction . . . . .
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1. INTRODUCTION 1.1 Introduction Sa
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1. Introduction 11 This phenomenon
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1. Introduction 13 1 2 initial mass
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1. Introduction 15 However, our pre
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2. SINGLE CRYSTAL GROWTH OF SODIUM
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2. Single crystal growth of sodium
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3. CRYSTALLIZATION UNDER WETTING/NO
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3. Crystallization under wetting/no
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4. NUCLEATION ON MINERAL SUBSTRATES
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4. Nucleation on mineral substrates
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Page 50 and 51: 4. Nucleation on mineral substrates
Page 52 and 53: 5. SODIUM SULFATE HEPTAHYDRATE FORM
Page 54 and 55: 5. Sodium sulfate heptahydrate form
Page 62 and 63: 6. CRYSTALLIZATION OF SODIUM SULFAT
Page 64 and 65: 6. Crystallization of sodium sulfat
Page 72 and 73: M 6. Crystallization of sodium sulf
Page 74 and 75: 7. THERMODYNAMIC AND POROMECHANIC C
Page 76 and 77: 7. Thermodynamic and poromechanic c
Page 92 and 93: 8. NMR COMBINED WITH ACCELERATED WE
Page 94 and 95: 8. NMR combined with accelerated we
Page 96 and 97: ∆ 8. NMR combined with accelerate
Page 106 and 107: 9. CONCLUSIONS AND OUTLOOK This cha
Page 108 and 109: 9. Conclusions and Outlook 107 Soft
Page 110 and 111: APPENDIX: CALCULATION OF SALT CRYST
Page 112 and 113: Appendix: Calculation of salt cryst
Page 114 and 115: Bibliography 113 [15] L.M. Luquer,
Page 116 and 117: Bibliography 115 [47] D. Rosenblatt
Page 118 and 119: Bibliography 117 [78] H.P. Huinink,
Page 120 and 121: LIST OF PUBLICATIONS Published: •
Page 122 and 123: ACKNOWLEDGMENT This thesis would no
Page 124: CURRICULUM VITAE Tamerlan Saidov wa
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