QUANTIFICATION OF PORE QUANTIFICATION OF PORE QUANTIFICATION OF PORE STRUCTURE CHARACTERISTICS STRUCTURE CHARACTERISTICS STRUCTURE CHARACTERISTICS FOR DETERIORATED MORTAR FOR DETERIORATED MORTAR FOR DETERIORATED MORTAR DUE TO CALCIUM LEACHING BY DUE TO CALCIUM LEACHING BY DUE TO CALCIUM LEACHING BY SYNCHROTRON SYNCHROTRON SYNCHROTRON MICROTOMOGRAPHY MICROTOMOGRAPHY MICROTOMOGRAPHY Takafumi SUGIYAMA (Hokkaido Univ.) Michael A. B. PROMENTILLA (Hokkaido Univ.) Takashi HITOMI (Obayashi Co. ) Nobufumi TAKEDA (Obayashi Co. )
Material Degradation in Long Material Degradation in Long Material Degradation in Long Term Service Term Service Term Service Calcium leaching Calcium leaching Degrading mechanical and Degrading mechanical and transport properties transport properties Change of pore structure Change of pore structure Sand and Clay characteristics characteristics Concret e Rock Cement it ious barrier Bent nit e Wast e Radioactive Waste Repository Radioactive Waste Repository
Development for calculation model of ion Development for calculation model of ion transport in hydrated cement system transport in hydrated cement system (SiTraM SiTraM in 2003) in 2003) ( Cl - C s C b Na + K + Ca 2+ C 0 C f Steady-state Ca 2+ leaching Cl - binding migration test OH - - - - - ∆Φ L + + + + + + - - - ∆Φ R Na + Ca 2+ Ca 2+ τ δ ε K + K + Na + Cl - Cl - Cl - ∂ = ∑ n C s − j Membrane Electrical J D ∂ i ij x = potential double layer j 1 Pore structure Ion-Ion Interaction in Ion-Solid characteristic pore solution Interactions
Significance of pore structure Significance of pore structure Significance of pore structure characteristics for material characteristics for material characteristics for material properties properties properties Strength Performance of Transport Properties of Cement-based Materials Cement-based Materials Pore Structure Characteristics 3D Micro-geometry Porosity, Diffusion Tortuosity
Pore Structure Characteristics of Cement-based Materials estimated from 3D Micro-geometry using Synchrotron Microtomography � Methodology: Synchrotron microtomography Random Walk Simulation � Application to deteriorated mortars and cement pastes � Accelerated electrical tests for calcium leaching
Synchrotron Synchrotron Synchrotron Microtomography Microtomography Microtomography Bentz et al 2000, Helfen et al. 2005, Lu et al. 2006, Burlion et al. 2006, Koster 2006, Gallucci et al. 2007 SPring-8 (Japan) •Same principle as medical CT scan – Creates X-ray image of ‘slice’ through object that can make 3D volume – But higher-energy, more focused Synchrotron-based X- rays (higher spatial resolution) – X-ray source is tunable, X-ray radiation is monochromatic, and X-ray beam is flat •Applications Geology, Anthropology, Biology, Medicine, Engineering ・ Advantage and Disadvantage 6/38
X-ray imaging of specimen SPring-8 3D reconstruction of image Pixel size = 0.5 micron SLICE (Nakano et al., 2007) 3D Image processing Pore segmentation Extraction of 3D pore space Pore cluster multiple labeling Mathematica program (Nakashima et al.2007) Visualization and quantification of porosity Quantification of tortuosity based on random walk simulation (RWS) 7/38
X ‐ ray Scanning of Specimen BL47XU X-Ray source Beam energy: 15 kev 2000x1300 px CCD Specimen 1500 projections (180 0 rotation) CCD Rotating Stage 8/38 １０００μ m
Mortar before deterioration Mortar before deterioration Water to cement ratio:0.5 Sand to cement ratio :2.0 Curing periods: 238days SLICE 400 100 µ m
Extraction of 3D image (VOI) Extraction of 3D image (VOI) Extraction of 3D image (VOI) 300 x 300 pixels in 2D 300 x 300 x 300 pixels (VOI) Based on REV (Representative Elementary Volume) analysis 150 µ m
Accelerated Electrical Method Accelerated Electrical Method Accelerated Electrical Method Direct current voltage Anode Cathode ２ ２ ＋ ＋ Ca Ca Electrode (SUS) Electrode (Pt) paste Cement ２ ２ ＋ ＋ Ca Ca Ion-change Ion-change water water Schematic diagram for Acceleration test underway accelerated electrical test using Acrylic cell 11/38
Distribution of CaO O/Si /SiO O 2 ratio in Distribution of Ca 2 ratio in Distribution of CaO/SiO 2 ratio in cement hydrate (obtained by cement hydrate (obtained by cement hydrate (obtained by EPMA) According to Saito et al. ACI Materials J. 1999 EPMA) EPMA) Diffusion test test Acceleration test test Diffusion Acceleration After 2,000days After 2,000days After 2months under 5 V/cm After 2months under 5 V/cm Inner side Surface Inner side Surface Inner side Cathode side Inner side Cathode side 2mm 2mm 8mm 8mm 6mm 6mm
Specimens under investigation Specimens under investigation Specimens under investigation W/C Cement Sand Chemical admixture Mortar 0.5 OPC Sieved under Super-plasticizer 210 µ m (S/C:2.0) Cement 0.5 OPC Non Viscosity agent paste (cellulose-ether type) OPC: Ordinary Portland Cement JIS R5210 Non-deteriorated mortar: 30 weeks in curing Deteriorated mortar: 20weeks in curing followed by acceleration test for 13weeks Cement paste: 20weeks in curing followed by acceleration test for13weeks 13/38
Non deteriorated Mortar Non deteriorated Mortar Deteriorated Mortar Deteriorated Mortar 150 µ m SLICE ５００ SLICE ５００
Porosity-Threshold dependency curve of VOI Deteriorated Mortar Deteriorated Mortar 1.0 0.010 At this transition point, the 0.9 0.009 segmented porosity started to increase rapidly 0.8 0.008 wherein the boundary segmented porosity 0.7 0.007 between pore and the norm. frequency solid matrix is most likely 0.6 0.006 to be segmented as pore space. 0.5 0.005 0.4 0.004 0.3 0.003 Threshold value for 0.2 segmentation 0.002 0.1 0.001 0.0 0.000 0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 15/38 GSV
16/38 Deteriorated Mortar (D.M.) Deteriorated Mortar (D.M.)
(a) Grayscale image (b) Segmented image 150 μ m D. M. D. M. (White for Solid, Black for Pore) Non Non D. M. D. M.
Quantification of porosity Quantification of porosity Quantification of porosity Segmented Connectivity Effective porosity, ε t γ porosity, ε e 0.39 0.98 0.38 0.04 0.51 0.02 ε t ε e ε t x γ Total pore voxels = = Total voxels γ No. of voxels of the largest percolating pore = Total pore voxels 18/38
Pore Cluster Multiple Labeling Hoshen-Kopelman Algorithm Binary Image Matrix (Pore GSV = 0) Labeled pore clusters 2 2 0 0 0 1 0 0 0 0 0 0 255 255 255 0 255 255 255 255 2 2 0 0 0 1 0 0 0 0 0 0 255 255 255 0 255 255 255 255 0 0 0 0 1 1 1 0 0 0 255 255 255 255 0 0 0 255 255 255 0 0 0 1 1 1 1 1 0 0 255 255 255 0 0 0 0 0 255 255 1 1 1 1 0 0 0 1 0 0 0 0 0 0 255 255 255 0 255 255 0 1 1 1 0 5 0 1 1 0 255 0 0 0 255 0 255 0 0 255 0 0 1 1 0 0 0 1 1 0 255 255 0 0 255 255 255 0 0 255 0 0 1 1 1 1 1 1 1 0 255 255 0 0 0 0 0 0 0 255 3 0 0 0 0 0 0 0 1 1 0 255 255 255 255 255 255 255 0 0 0 4 0 0 0 0 0 0 0 1 255 0 255 255 255 255 255 255 255 0 19/38
Diffusion Tortuosity and Random Walk Time-dependent diffusion coefficient To probe the geometry of of random Brownian motion of molecules porous media ( ) ( ) ( ) 2 ′ ′ ⎡ ⎤ = − = 2 r r t r 0 2 dD t t ⎣ ⎦ MSD For 3D random walk (d =3) D τ = 0 Diffusion Tortuosity D ( t ) Free space (porosity = 100 %) Pore space (restricted diffusion) 2 2 r d r 1 1 = = D D ( t ) 0 6 t 6 dt 20/38
Pore structural model: Capillary model Pore space : Diffusion tortuosity D = Le o Tortuosity = Tortuosity Le D ∞ L Unrestricted L ( ) = D t D open 0 diffusion system MSD Unidimensional: ( ) < D t D closed percolating in the x-direction 0 Restricted system diffusion τ ≥ 1 f 2 ⎛ ⎞ Le τ = ⎜ time,t ⎟ f ⎝ ⎠ Mean square displacement vs time L 21/38
Time-Dependent Diffusion Tortuosity Free space 1 ( ) 1 D t τ = Open pore D 0 Closed pore 0 t: diffusion time 22/38
20 20 20 Y Y Y Y Y Y 10 10 10 10 10 10 0 0 0 0 0 0 -10 0 -10 0 -10 0 20 20 20 10 10 10 Z Z Z 0 0 0 -10 -10 -10 -10 -10 -10 -10 -10 -10 0 0 0 0 0 0 10 10 10 10 10 10 X X X X X X ( ) 20 ( ) 20 20 τ = τ = τ = 2 2 2 . 78 1 . 00 2 . 40 ⎛ ⎞ = ⎛ ⎞ = ⎛ ⎞ = Le Le Le ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ 1 2.40 ? ⎝ ⎠ ⎝ ⎠ ⎝ ⎠ L L L 23/38
Deteriorated Mortar Deteriorated Mortar A sample trajectory of a random walker in 3D pore space of DM 400 400 Y Y 200 200 0 0 -200 -200 400 200 Z 0 -200 Percolating pore= 0.38 -200 -200 (98% of Porosity) 0 0 2 million time steps 2 million time steps 200 200 X X 50,000 walkers 400 400 50,000 walkers Diffusion tortuosity: 4 24/38
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