Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Micro-spectroscopic investigations of the Al and S speciation in hardened cement paste 1 ,R. Dähn 1 , B. Lothenbach 2 , M. Vespa 1 E. Wieland 1 Paul Scherrer Institute, Laboratory for Waste Management, Villigen PSI, Switzerland 2 Empa, Laboratory for Concrete & Construction Chemistry, Dübendorf, Switzerland 2 th International Workshop on Waste/Cement Interactions October 12-16, Le Croisic, France Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Layout � Introduction � Materials and methods � Al and S speciation in cementitious materials ● Al speciation - References - Micro-spectroscopic studies ● S speciation - References - Micro-spectroscopic studies � Conclusions Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Background Waste package (cement & steel) Cement – important component of the engineered barrier system of the repositories for low- (L/ILW) and intermediate-level wastes (ILW) Hardened cement paste: ~ 20 wt% Deep geological repository Container Cavern backfill (concrete, mortar, steel) (porous mortar) Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Example: Ni uptake by cement � Combination of BSE (SEM) with µ-XRF/XAS � Information on the morphology and the chemical composition of phases on the same spot BSE-image BSE-image µ-XRF /LUCIA Si Inner CSH Portlandite 100 µ m Ni spot 100 µ m µ-XRF/LUCIA µ-XRF/ALS Belite Al Ni, Ca Outer CSH 100 µ m Belite 50 µ m 100 µ m Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Motivation � X-ray absorption fine structure (XAFS) spectroscopy as complementary tool to XRD for cement phase characterization? � In situ identification of single cement phases with micro-scale resolution in hardened cement paste? � Identification of uptake-controlling cement phase in connection with metal cation and anion binding in hardened cement paste? Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Hardened Cement Paste (HCP) Sulphate-resisting cement: CEM I 52.5 N HTS Clinker phases in non hydrated cement wt%: Alite 3CaO ⋅ SiO 2 61 Belite 2CaO ⋅ SiO 2 18 Aluminate 3CaO ⋅ Al 2 O 3 3.9 Ferrite 4CaO ⋅ Al 2 O 3 ⋅ Fe 2 O 3 5.8 Calcite CaCO 3 3.7 Gypsum, Anhydrite CaSO 4 3.6 Others ≤ 4 plain light + H 2 O Hydration products in wt% (w/c = 0.4; 1 y hydration): Calcium silicate hydrate (C-S-H) ~49 Portlandite ~20 Calcium aluminates (AFt, AFm) ~19 Hydrotalcite ~2 CaCO 3 ~2 Minor phases ( Fe, Mn oxides) <1 Non-hydrated clinker minerals ~8 Lothenbach & Wieland 2006 crossed polars Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Materials � References - S: Gypsum CaSO 4 - Al: Aluminate C 3 A - Al: Ferrite C 4 AF - Al/S: Ettringite, Fe-Ettringite - Al/S: AFm (C 4 AH 13 ), Monosulfate, Monocarbonate - Al: Hydrogarnet, Si-Hydrogarnet - Al: Hydrotalcite � Cement - CEM I 52.5 N HTS (Lafarge, France) � Hardened cement pastes (HCP) - HTS cement hydrated at 5°, 20°, and 50° for 28 days Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Sample Preparation for Micro and Bulk XAS Studies Hydration Cement 5°/20°/50° dry, impregnate, cut, polish References Thin sections Clinkers of HCP (<63 µ m) µ -XRF/XAS „Bulk“-XAS @ Lucia/SLS @ Lucia/SLS Beamsize: ~5 x 5 µ m 2 Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Sample Preparation Incident beam � Powder materials Fluorescence radiation Pellets � Thin sections Fluorescence Incident beam radiation Silver spot Glass support Note: Probed volume at the given energy: ~5×5×1 µm 3 Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT X-ray Absorption Fine Structure (XAFS) Spectroscopy Detection methods I 0 I = e µ x Transmitted beam Fluorescence X-ray photons Incident X-ray beam Spectra - regions Photon - Matter interaction EXAFS e - 1 XANES Absorption (µx) Fluorescence region region 6d 0,8 Absorption 0,6 L III 0,4 γ Edge 0,2 2p 17600 17800 18000 18200 18400 18600 18800 E ( eV) Photon energy (E) Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT X-ray Absorption Fine Structure (XAFS) Spectroscopy X-ray Absorption Near Edge Structure; XANES Extended X-ray Absorption Fine Structure, EXAFS Absorption a.u Al Interference of Si edge@1839 eV with the Al EXAFS S Pre-edge limited structural information on the chemical environment -200 0 200 400 600 800 1000 E 0 : photoelectron threshold energy Al K: E 0 = 1559.6 eV Relative Energy [eV] S K: E 0 = 2472 eV Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT XANES Data Analysis � Features - XANES range: to an energy of about 50 eV above the edge - XANES states: Excited electron populate higher unoccupied states (unoccupied bound states and low-lying continuum states in complex ions etc.) - XANES regime: - electronic and geometric structure - multiple-scattering events - average valence of absorber atom � Experimental consistency checks - Same reference measured on different campaigns - Same compounds prepared by different groups - Spectra of similar compounds Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Reproducibility Si-Hydrogarnet: -Two campaigns in June 2007 and April 2008 at the Lucia beamline@SLS 4 Si-Hydrogarnet (Jun 07) Si-Hydrogarnet (Apr 08) Normalized Absorbance 3 2 1 0 -1 1.56 1.58 1.6 1.62 1.64 1.66 Energy [keV] Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Variability in C 3 A C 3 A: - XANES data of C 3 A prepared in different laboratories 2.5 2 Normalized Absorbance C3A_PSI C3A_TM 1.5 1 0.5 0 1.56 1.58 1.6 1.62 1.64 1.66 Energy [keV] Matschei et al. 2007 Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Consistency of AFt Spectra Fe-ettringite: - Spectrum of Al/Fe-ettringite-ss - Spectrum calculated based on ettringite 3 Fe-Ettringite Abs (au) 2.5 Ettringite spectrum - Normalized Absorbance corrected Fe-ettringite 2 1.5 1 0.5 0 1.56 1.58 1.6 1.62 1.64 1.66 Energy [keV] Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT Aluminium speciation Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT HTS Modelling 5 °C 70 pore solution 65 60 55 50 45 3 /100 g cement C-S-H 40 35 gypsum 30 C 4 AF C 3 A ettringite 25 cm C 2 S 20 monocarbonate calcite 15 hydrotalcite portlandite C 3 S 10 5 0 1E-3 0.01 0.1 1 10 100 1000 Lothenbach et al. 2007 hydration time [days] Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT HTS Modelling 20 °C 70 pore solution 65 60 55 50 45 3 /100 g cement C-S-H 40 35 gypsum 30 C 4 AF C 3 A ettringite 25 cm C 2 S 20 monocarbonate calcite 15 hydrotalcite portlandite C 3 S 10 5 0 1E-3 0.01 0.1 1 10 100 1000 Lothenbach et al. 2007 hydration time [days] Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT HTS Modelling 50 °C 70 pore solution 65 60 55 50 45 3 /100 g cement 40 C-S-H 35 gypsum 30 ettringite C 4 AF C 3 A 25 cm monosulfate C 2 S 20 calcite 15 hydrotalcite C 3 S 10 portlandite 5 0 1E-3 0.01 0.1 1 10 100 1000 Lothenbach et al. 2007 hydration time [days] Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
Nuclear Energy and Safety Research Department Laboratory for Waste Management PAUL SCHERRER INSTITUT References - Hydrogarnets Si-hydrogarnet: C 3 ASH 4 Hydrogarnet: C 3 AH 6 6 Si-Hydrogarnet 5 Hydrogarnet Normalized Absorbance 4 3 2 1 0 1.56 1.58 1.6 1.62 1.64 1.66 Energy [keV] Paul Scherrer Institut CH-5232 Villigen PSI WCI-2 2008
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