Thermodynamic modelling

Transcription

1 Thermodynamic Modelling and influence of solid solutions Barbara Lothenbach Empa Laboratory for Concrete & Construction Chemistry Dübendorf, Switzerland Thermodynamic modelling 1. Thermodynamics chemical equilibria modelling software databases 2. Cement hydration 3. Influence of limestone 4. Influence of temperature 5. Solid solutions 6. Blended cements 1

2 Volume [cm 3 /1 g cement] Why thermodynamic modelling? pore solution gypsum brucite C 4 AF C3 A C 2 S C 3 S monocarbonate portlandite C-S-H porosity Hydration time [days] => Understanding => Quantitative predictions chemical shrinkage Thermodynamic modelling Chemical equilibria: Gypsum: CaSO 4 2H 2 O Reaction: CaSO 4 2H 2 O Ca 2+ + SO 4 +2H 2 O Ca 2+ SO 4 Solubility product K S = {Ca 2+ } {SO 4 } {H 2 O} 2 /{CaSO 4 2H 2 O} K S = {Ca 2+ } {SO 4 } = H 2 O Gypsum: CaSO 4 2H 2 O {} : activity; []: concentration {Ca 2+ } = [Ca 2+ ] γ Ca2+ log Ca 2 2 AZ 1 Ba I bi I 2

3 Thermodynamic modelling Chemical equilibria: Gypsum: CaSO 4 2H 2 O Ca 2+ CaOH + OH - H 2 O CaSO 4 SO 4 H + Reaction: CaSO 4 2H 2 O Ca 2+ + SO 4 +2H 2 O Solubility product K S = {Ca 2+ } {SO 4 } {H 2 O} 2 /{CaSO 4 2H 2 O} K S = {Ca 2+ } {SO 4 } = Equilibrium constants K = {CaOH + }/{Ca 2+ } {OH - } = K = {CaSO 4 }/{Ca 2+ } {SO 4 } = K = {H + } {OH - } = Gypsum: CaSO 4 2H 2 O Thermodynamic modelling Chemical equilibria: Gypsum KOH 1 Concentration of Ca, SO 4? 2 What happens if we add KOH?? SO Ca 2+ 4 CaOH + OH - H 2 O CaSO 4 H + Solubility products K S = {Ca 2+ } {SO 4 } = K S = {Ca 2+ } {OH - } 2 = Equilibrium constants K = {CaOH + }/{Ca 2+ } {OH - } = K = {CaSO 4 }/{Ca 2+ } {SO 4 } = K = {H + } {OH - } = Gypsum: CaSO 4 2H 2 O 3

4 Solubility of gypsum Gypsum K S = {Ca 2+ } {SO 4 } = {Ca 2+ } = {SO 4 } = /2 {Ca 2+ } = *[Ca 2+ ] =.42*[Ca 2+ ]; [Ca 2+ ] = /.42=.12 {CaSO 4 } = {Ca 2+ } {SO 4 } * Dissolved complexes Ca tot = [Ca 2+ ] * Ca2 / CaSO * [Ca 2+ ] 2 = [Ca 2+ ] * [Ca 2+ ] 2 = *.12 2 =.17 mol/l Ca tot = SO 4 tot = 17 mmol/l => Calculation easier with geochemical softwares Solubility of gypsum Gypsum Portlandite +KOH? 4

5 Solubility of portlandite Ca Portlandite OH - Plus CO 2 Chemical equilibria: Gypsum CaO CO 2 Ca 2+ CaOH + OH - H 2 O Portlandite Gypsum CaSO 4 SO 4 CaCO 3 CaHCO 3 + H + Calcite Solubility products K S = {Ca 2+ } {SO 4 } = K S = {Ca 2+ } {OH - } 2 = K S = {Ca 2+ } {CO 3 } = Equilibrium constants K = {Ca 2+ } {OH - }/{CaOH + } = K = {Ca 2+ } {SO 4 }/{CaSO 4 } = K = {H + } {OH - } = K = {Ca 2+ } {CO 3 }/{CaCO 3 } = K = {Ca 2+ } {HCO 3- }/{CaHCO 3+ } = EPFL Master Course, 212 5

6 Gypsum Portlandite Addition of CO 2 EPFL Master Course, 212 Codes Complex systems Geochemical codes needed for calculation: Geochemical database User interface: problem formulation Problem solving 6

7 Geochemical Codes Freeware GEMS solid solution, transport modelling upon request GEMS 3 can be downloaded PHREEQC transport modelling Commercial products MINEQL+ MINTEQA2 CHESS Thermodynamic databases general-tdb Cement data Aqueous phase (Ca 2+, Ca(OH) +, ) AFm AFt hydrogarnet C-S-H Gaseous phase (e.g. CO 2 (g),...) Minerals (calcite, gypsum, portlandite, ) SO 4 -AFm solid solution OH-AFm CO 3 -AFm hemicarb. strätlingite Al-AFm solid solution Fe-AFm SO 4 -AFt solid solution CO 3 -AFt thaumasite Fe-AFt solid solution Al-AFt C 3 AH 6?? C 3 AS x H y jennite solid solution tobermorite SiO 2 7

8 Database 1 Geochemical database (generally integrated in software) Complex formation: CaOH +, CaHCO 3+, Solubility products: gyspum, calcite,. Specific cement database Solubility hydration products (, monosulphate, ) Babushkin et al. (1985) Thermodynamics of Silicates, Springer Reardon, E.J. (1992) Waste Management 12, Atkins et al. (1992) Cement Concrete Reasearch 22, CEMDATA7: Matschei et al. (27) Cement Concrete Reasearch 37, ; Lothenbach et al. (28) Cement Concrete Reasearch 38, Blanc et al. (21) Cement Concrete Reasearch 4, ; Recent additions: Thaumasite: Schmidt ea (28) Cement Concrete Reasearch 38, Friedel s salt: Balonis ea (21) Cement Concrete Reasearch 4, Hydrotalcite: Rozov ea (21) Cement Concrete Reasearch 4, Fe-monocarbonate: Dilnesa ea (211) Cement Concrete Reasearch 41, New C-S-H model: Kulik (211) Cement Concrete Reasearch 41, Current work: hydrotalcite (Rozov), Fe-hydrates (Dilnesa), C-A-S-H (L Hopital ea), Database 2 Geochemical database and specific cement database have to be consistent! Use the specific cement database only with the correct geochemical database! Data formats: Log K values (PHREEQC, GEMS, MINEQL, ) ΔG f (Gibbs free energy of formation) (GEMS, MTDATA, ) Gr RT convertible: K e G r i G i f 8

9 cm 3 /1 g cm 3 /1 g Database Cemdata % 6 monosulfate 5 hydrotalcite 4 hemicarbonate monocarbonate calcite Monosulfate 3 Ettringite 2 1 year C 4 AF portlandite Ettringite 1 year Hemicarbonate Monocarbonate C 4 AF 7 days 1 C-S-H 7 days 1 day day wt% CaCO Matschei ea Angles 27, 2q CCR (degrees) 37; Lothenbach CuKa ea 28, CCR 38; Damidot ea Angles 2112q CCR (degrees) 41 CuKa Databases: Blanc Kinetic effect? 7 +7% 6 Hydrogarnet 5 hydrotalcite 4 hemicarbonate monocarbonate calcite 3 portlandite 2 1 Different data > different results C-S-H wt% CaCO 3 Blanc ea 21, CCR 4 9

10 Different databases Cemdata Blanc Ettringite 6Ca 2+ +2AlO SO 4 + 4OH - + 3H 2 O Monosulfate 4Ca 2+ +2AlO SO 4 + 4OH - + 1H 2 O C 3 AH 6 3Ca 2+ +2AlO OH - + 4H 2 O Monocarb. 4Ca 2+ +2AlO CO 3 + 4OH - + 1H 2 O Analytical error ±.5-1 Reardon Waste Management 12, 1992 Cemdata7: Lothenbach Winnefeld CCR 36 26; Matschei ea CCR 37, 27; Lothenbach ea CCR 38, 28; Möschner ea CCR 39, 29; Schmidt ea CCR 38, 28 Blanc ea CCR 4, 21 Solubility of C 3 AH 6? 1

11 Carbonation! Peppler and Wells observed in some samples calcite as CO 2 had leaked through their rubber stoppers Solubility of C 3 AH 6 Log K s C 3 AH 6 = {Ca 2+ } 3 {Al(OH) 4- } 2 {OH - } 4 = Carbonation! 11

12 Thermodynamic modelling 1. Geochemical programme 2. Thermodynamic data 3. Problem formulation: Define quantities of water, solids: gypsum, calcite, C 3 A, C 3 S, liquids: H 2 SO 4, gas: CO 2, N 2, at the user interface of the respective programme Input 12

13 Results Solids: amount in g, mol, cm3, Concentrations (mg/l, mm, ) Results Concentrations (mg/l, mm, ) 13

14 Modelling of cement hydration 1. Chemical/mineralogical composition 2. Dissolution of clinker 3. Calculation of stable hydrates 4. Calculation of aqueous concentrations Portland cement: CEM I 42.5 N Chemical analysis Phases SiO 2 19 Alite C 3 S 58 Al 2 O Belite C 2 S 1 Fe 2 O alum. C 3 A 7.6 CaO 62 ferrite C 4 AF 7.5 Bogue CaO free.6 calculations CaSO MgO 1.4 CaCO3 4.8 K 2 O.95 K 2 SO Na 2 O.1 Na 2 SO 4.1 SO 3 3. CO

15 Diff. relative weight [%/K]. relative weight [%] Chemical reactions Alite (C 3 S) + water C-S-H + portlandite (CaO) 3 SiO H 2 O Ca 1.7 SiO 2 (H 2 O) Ca(OH) 2 C 3 S + 5.3H C-S-H + 1.3CH C/S Belite (C 2 S) + water C-S-H + portlandite (CaO) 2 SiO H 2 O Ca 1.7 SiO 2 (H 2 O) 4 +.3Ca(OH) 2 C 2 S + 4.3H C-S-H +.3CH Aluminate (C 3 A) + anhydrite (Cs) + water (CaO) 3 Al 2 O 3 + 3CaSO H 2 O (CaO) 3 (CaSO 4 ) 3 Al 2 O 3. 32H 2 O C 3 A + 3Cs + 32H C 6 As 3 H 32 AFt Aluminate (C 3 A) + calcite (Cc) + water monocarbonate (CaO) 3 Al 2 O 3 + CaCO H 2 O (CaO) 3 (CaCO 3 ) Al 2 O 3. 12H 2 O C 3 A + Cc + 12H C 4 AcH 12 AFm C CaO S SiO 2 A Al 2 O 3 F Fe 2 O 3 H H 2 O c CO 2 s SO 3 N Na 2 O K K 2 O M MgO T TiO 2 AFt + AFm contain a lot of water -> high volume PC hydration:tga 1 95 unhydrated 1 h 3 h 6 h 9 1 day gypsum/hemihydrate 28 days 15 days. C-S-H AFm / hydrotalcite calcium CaCO 3 monocarbonate Ca(OH) temperature [ C] 15

16 Force counts / - PC hydration: XRD year 28 d 1 d portlandite portlandite 1 unhydrated 5 gypsum ferrite gypsum clinker 3 phases 35 theta / Pore solution chemistry Cut Teflon filter Pore solution 16

17 Effective saturation index Pore solution [mm] 1 OH - Na Ca S K.1 Si.1 Al time [days] Calculation of saturation indices Amorphous AH 3 saturation Saturated Undersaturated undersaturation SF-Gr undil SF-Gr dil Phase in equilibrium with pore solution Might form Phase not in equilibrium with pore solution Cannot form Dissolve Time (hours) Measured: total Ca concentrations from = Ca 2+ + CaOH + +CaSO 4 +. IAP 2 2 Ca OH measured SI log K log S K concentrations GEMS: calculates {Ca 2+ } (activity) S portlandit e theoretical taking into account complex IAP ion activity product solubility formation with other ions (OH -, derived from measured concentrations SO 4, ) and influence of ionic strength, 17

18 effective saturation index saturation index Calculation of saturation indices gypsum portlandite Phase in equilibrium with pore solution Might form Phase not in equilibrium with pore solution Cannot form Dissolve time (days) 1 Portlandite: K s = {Ca 2+ }{OH - } 2 Ettringite: K s = {Ca 2+ } 6 {SO 4 } 3 {Al(OH) 4- } 2 {OH - } 4 {H 2 O} 26 SI depends on the number of reacting ions Calculation of effective saturation indices 1.5 portlandite Effective saturation inidices consider the number of dissolved species interacting -> better comparable gypsum time (days) 1 1 IAP 1 eff SI log n K log S 3 IAP ion activity product derived 2 2 Ca OH K S portlandit e from measured concentrations measured theoretical solubility 18

19 effective saturation index effective saturation index Calculation of effective saturation indices portlandite 1-1 gypsum.5 jennite-like C-S-H time (days) tobermorite-like C-S-H time (days) 1 Modelling of Hydration clinker clinker C-S-H Portlandite Ettringite 19

20 Equilibrium Thermodynamic modeling 1 Portland cement Multi-component input I Clinkers C 3 S C 2 S C 3 A C 4 AF II Other solids K 2 O Na 2 O MgO K 2 SO 4 Gypsum Na 2 SO 4 Anhydrite Hemihydrate Calcite CaO III Water H 2 O Hydrated OPC C-S-H portlandite? monosulfate monocarbonate hydrotalcite 2 Thermodynamic modelling Equilibrium calculations with geochemical software: PHREEQC GEMS Ca 2+ CaOH + OH - H 2 O CaSO 4 SO 4 H + Portlandite Ca(OH) 2 Gypsum: CaSO 4 2H 2 O Complex formation K = {CaOH + }/{Ca 2+ } {OH - } = K = {CaSO 4 }/{Ca 2+ } {SO 4 } = K = {H + } {OH - } = Solubility products K S = {Ca 2+ } {SO 4 } = K S = {Ca 2+ } {OH - } 2 =

21 Concentration [mmol/l] g/1 g 3 clinker dissolution Empirical Approach: Parrot and Killoh (1984) K1 Rt N t 1 K2 Rt 1 R K 3 1 N 1 1a ln(1 a ) 1 at 1/ 3 1 at N 1 a 3 2 / 3 All parameters (K i, N i ) from Parrot and Killoh (1984) t t t alite belite ferrite // time (days) aluminate Input: Surface area, w/c, composition Modeled pore solutions Na OH - Ca K 1 S.1 Si.1 Al time [days] 21

22 Al-, SO 4 - and CO 3 -hydrates 12 1 C 3 A + 3gypsum 3CaO. Al 2 O 3. 3CaSO 4. 32H 2 O 3CaO. Al 2 O 3. 3CaSO 4. 32H 2 O 8 [g/1 g solid] 6 gypsum C 3 A monocarbonate 3CaO. Al 2 O 3. CaCO 3. 11H 2 O 4 2 CaCO 3 brucite hydrotalcite time [days] Ca- and Si-Hydrates pore solution alite C-S-H (ss) [g/1 g solid] 3 2 belite Ca(OH) time [days] 22

23 cm 3 /1 g cement cm 3 /1 g cement 45 OPC without calcite pore solution gypsum C 4 AF C 3 A C2 S C 3 S porosity chemical shrinkage C-S-H monosulfate portlandite 1E hydration time [days] 46 OPC without calcite pore solution gypsum C 4 AF C 3 A C2 S C 3 S porosity chemical shrinkage Ettringite 1 year C-S-H 7 days monosulfate portlandite Monosulfate C 4 AF 1 day 1E hydration time [days] Angles 2q (degrees) CuKa 23

24 Volume [cm 3 /1 g cement] 47 OPC with calcite pore solution porosity gypsum brucite C 4 AF C3 A C 2 S C 3 S chemical shrinkage Ettringite portlandite 1 year C-S-H 7 days monocarbonate Hemicarbonate Monocarbonate 5 1 day Hydration time [days] Angles 2q (degrees) CuKa C 4 AF Influence of limestone (CaCO 3 ) Filler CEM I contains up to 5% of limestone CEM II /A-L (or A-LL) contains up to 6-2% of limestone CEM II /B-L (or B-LL) contains up to 21-35% of limestone Acceleration Stark et al., ibausil 26 Reaction Monocarbonate: (CaO) 3 (CaCO 3 ) Al 2 O 3. 11H 2 O CaCO 3 + C 3 A + 11H C 4 AcH 11 24

25 Limestone & cement hydration Ettringite 1 year 7 days 1 day PC4 PC Monosulfate Hemicarbonate Monocarbonate C 4 AF Angles 2q (degrees) CuKa with limestone without limestone Main difference: AFm phases [Ca 2 (Al, Fe)(OH) 6 ] 2 2+ Monosulfate [SO 4, 6H 2 O] Monocarbonate [CO 3, 5H 2 O] Hemicarbonate [.5CO 3, OH, 5.5H 2 O] Courtesy of Gwenn Le Saout Lothenbach et al., 28, Cement Concrete Research 38, Volume differences Presence of limestone 3 C 4 AsH Cc + 18H C 6 As 3 H C 4 AcH 11 3*39 + 2*37+18* *262 H 2 O Cc MS Ettringite + Monocarbonate The presence of small quantities of limestone (4%) stabilises monocarbonate and results in a higher degree of space filling less porosity higher compressive strength High quantities of limestone (> ~15%) will increase porosity decrease compressive strength 25

26 strength [N/mm 2 ] cm 3 /1 g compressive strength [MPa] Influence of limestone on PC 7 +7% 6 monosulfate 5 hydrotalcite 4 hemicarbonate 8 monocarbonate 7 6 calcite 3 portlandite wt% Al 2 O 3 3 Herfort 1: 5.% Al2O3 1 C-S-H Herfort 2: 4.2% Al2O3 2 Herfort 3: 4.4% Al2O3 De Weerdt, 21 1 De Weerdt, 211a De Weerdt, b 1 wt% CaCO Damidot ea 211 CCR 41; Lothenbach ea 28, CCR 38; Matschei ea limestone 27, CCR [%] 37 4 Influence of temperature: Compressive strength C 2 C 3 C 4 C age [d] 26

27 Relative XRD peak heigth Heat of hydration / J/(g h)) Calorimetry C C 5 5 C Time (h) Progress of hydration 6 // alite 5 C 2 C 5 C 2 1 // time (days) 27

28 5 C, 15 days 5 C, 15 days AFm 28

29 Diff. relative weight [%/K] relative weight [%] Counts XRD, 15 days 3 25 monosulfate 2 5 C 15 monocarbonate portlandite 1 2 C Position [ 2Theta] 5 C TGA, 15 days unhyd. 5 C 2 C 5 C 7 gypsum. C-S-H monosulfate CaCO 3 monocarbonate -.5 portlandite temperature [ C]

30 log K g/1 g Modeling: Temperature Arrhenius equation R T A e Ea RT // alite 5 C 2 C 5 C E a : activation energy // time (days) Chemical reactions accelerate with increasing temperature Solubility of as f(t) logk T A A2T A3 lnt calculated Damidot and Glasser, 1992 Damidot and Glasser, 1993 Warren and Reardon, 1994 Perkins and Palmer, 1999 Macphee and Barnett, Lothenbach ea 28, CCR 38 Temp [ C] 3

31 cm 3 /1 g cement calc. solubility product log Ksp Solubility of monosulfate -28 1) -29 3) 2) 4) 3) 3) -3 5) 6) 1) D'Ans )Zhang 2 2) Jones )Zhang ) Atkins )Kalousek Temperature [ C] Matschei et al. 27, CCR 37 Hydration modelling at 2 C monocarbonate calcite hydrotalcite gypsum C 4 AF C 3 A C 2 S C 3 S C-S-H portlandite time [days] 31

32 cm 3 /1 g cement cm 3 /1 g cement Hydration modelling at 5 C monocarbonate calcite hydrotalcite gypsum C 4 AF C 3 A C 2 S C 3 S C-S-H portlandite time [days] Hydration modelling at 5 C 6 15 days 5 monosulfate 4 calcite hydrotalcite CaSO 4 3 C 4 AF C 3 A 2 C 2 S 1 C 3 S C-S-H portlandite time [days] 32

33 Compressive strength (N/mm 2 ) cm 3 /1 g 15 Tagen: HR 6 little C 3 A monocarbonate portlandite C-S-H monosulfate calcite 1 5 hydrotalcite unhyd. clinker Lothenbach ea 28, CCR 38 Temperature [ C] Al/SO 4 = 1.9 Strength-porosity C 3 C 2 C 5 C measured calculated Strength= 144*(1-.39*porosity) R 2 =.91 % 1% 2% 3% Total porosity (vol%) 33

34 Influence of temperature Higher temperature: kinetic of hydration morphology (inhomogenous), denser IP coarser porosity pore solution (SO 4, Al) hydrates (, monocarb. monosulfate) volume decrease decrease in strength Solubility of increases with temperature -> less stable Thermodynamic modelling: influence of solid solutions 34

35 Solid solutions C-S-H: jennite-tobermorite AFm phases: e.g, C4AH13-C4AsH12 AFt phases: e.g. Al- Fe- In cement systems important phenomena Solid solutions Solid solution is a homogeneous crystalline structure in which one or more types of atoms or molecules may be partly substituted for the original atoms and molecules without changing the structure, although the lattice parameters may vary. (Bruno et al., 27) Example: CaCO 3 (aragonite) - SrCO 3 (strontianite) Bruno, J., Bosbach, D., Kulik, D., Navrotsky, A. (27) Chemical Thermodynamics. Vol 1. Chemical Thermodynamics of Solid Solutions of Interest in Radioactive Waste Management. OECD Nuclear Energy Agency Data Bank, North Holland Elsevier Science Publishers B. V., Amsterdam, The Netherlands. 266 p. 35

36 Intensity 5 cps SO4/(SO4+2OH)-ratio [-] concentration [mmol/l] ph [-] Characteristics of solid solution: - peak shift in XRD - continuous change of concentrations supersaturation mixed endmembers undersaturation Series2 2 phases 1 phase Al Ca C 4 AH x calc. SO 4 / (SO 4 +2OH)-ratio C 4 AsH phases 1 phase Matschei et al (27) 11.8 supersaturation mixed endmembers undersaturation C 4 AH x calc. SO 4 / (SO 4 +2OH)-ratio C 4 AsH 12 Effects of solid solution: - stabilizes solids - lowers aqueous concentrations C4AH13 monosulfate: solid solution Characteristics of solid solution: - peak shift in XRD - continuous change of concentrations M H M M, H C3AH6 H - Hydroxy-AFm type ss M- Monosulfate type ss hydroxy-afm CuKa] monosulfoaluminate From Matschei et al (27) CCR 37,

37 interplanar spacings d 1 [Å] this work Poellmann SO 4-AFm-type ss OH-AFm-type ss C 4 AH x calc. SO 4 /(SO 4 +2OH) ratio C 4 AsH 12 From Matschei et al (27) CCR 37, AFm solid solutions C-S-H: jennite-tobermorite AFm: C4AH13-C4AsH12 Matschei ea 27 37

38 Solid solutions probable AFm: 4CaO Al 2 O 3 CaX nh 2 O CO 3 H 2 O Similar charge Similar structure Similar size Monocarbonate: 4CaO Al 2 O 3 CaCO 3 11H 2 O CO 3 Monosulfate: 4CaO Al 2 O 3 CaSO 4 12H 2 O SO 4 [Ca 4 Al 2 (OH) 12 ] 2+ Renaudin 1999 Solid solution CO 3 -AFm SO 4 -AFm? Ettringite Monosulfate Monocarbonate C 4 AF Angles 2q (degrees) CuKa Main difference: AFm phases [Ca 2 (Al, Fe)(OH) 6 ] 2 2+ Monosulfate [SO 4, 6H 2 O] Monocarbonate [CO 3, 5H 2 O] Solid solution not probable: Similar charge Similar structure - Similar size - 38

39 Ca, Si [mmol/l] mole fraction C-S-H solid solution: Ca-rich and Ca-poor C-S-H C-S-H solid solution 1% 8% 6% tobermorite-like Ca-poor C-S-H amorphous SiO2 jennite-like Ca-rich C-S-H portlandite Ca-rich C-S-H: (CaO) 1.67 SiO 2 H 2 O 2.1 Ca poor C-S-H: (CaO).83 SiO 2 H 2 O 1.3 Reduction in CaO and H 2 O 4% 2% % Ca/Si in solids slag fly ash OPC C-S-H solid solution: jennite-tobermorite Flint&Wells (1934) Fujii&Kondo (1981) Roller&Erwin (194) Greenberg&Chang (1965) Courault (2) Glasser et al. (25) Chen&Morris (1972) Barbarulo (22) Taylor (195) Ca 1 solid solution no solid solution 5 Si molar Ca/Si-ratio in solids 39

40 Blended cements OPC with slag, fly ash, pozzolans, SiO 2, Big constructions: dams, Dense structure More durable Lower ph -> Radwaste Shotcrete UHPC SiO 2 wt% silica fume fly ash C F Natural pozzolans metakaolin slag CaO Portland cement fine limestone Al 2 O 3 4

41 PC SF SiO 2 wt% SiO 2 gel C-S-H: C/S.83 C-S-H: C/S 1.7 C-A-S-H C 3 ASH 4 strätlingite Al(OH) 3 gel CaO portlandite AFt AFm C 3 AH 6 Al 2 O 3 1) PC-silica fume 2% alkali free accelerator: ~ 1 Al 2 O 3 : 1 SO 3 4% 6% 41

42 counts / - cm 3 /1 g Influence of SiO monocarbonate C hydrotalcite 3 FS.84 H 4.32 portlandite gypsum calcite 3 2 C-(A-)S-H 1 83 PC SiO g SiO 2 / 1 g 4% SiO days 36 days 56 days 7 days 1 day 1 h unhydrated Ettringite Gypsum ferrite A + $ + 2C$ + 4C -> C 6 A$ 3 H 32 XRD Anhydrite Alite Alite/ belite 35 theta / Hemicarbonate 1-56 days Portlandite Monocarbonate 1-7 days E E E Hemicarbonate E E C-S-H belite C 3 A 42

43 Diff. relative weight (%/K) relative weight (%) TGA gypsum 1 h C-S-H 36 days 21 days 7 days unhydrated hemicarbonate 1-56 days max. 4 days 36 days ESDRED 7days temperature ( C) 2 days 1 day 4 days portlandite 1-14 days max. 4 days 14 days unhydrated 1 h CaCO 3 unhydrated 1 hour.15 2 hours 4 hours 6 hours 1 day.1 2 days 4 days 7 days.5 14 days 28 days 56 days. 21 days 36 days Silica fume Q 4 Reactivity of SiO 2 anhydrous cement Q Si-NMR Q 1 Q 2 43

44 silica fume [g/1 g] Na + K [mm] silica fume [g/1 g] Reaction of silica fume 5% 45% dissolution of silica fume 4% initial amount of silica fume 35% 3% 25% 2% 15% 1% 5% % time [days] 5% 45% 4% 35% 3% 25% Silica fume alkali uptake -> more C-S-H + low Ca/Si C-S-H -> more alkali uptake initial amount of silica fume silicafume Na + K % 15% 1% % 5 % time [days] 44

45 effective saturation index mol/l Composition of the pore solution ESDRED (CEM I 42.5 N + SF + Sigunit).25 K, Na => in C-S-H Low C/S => more K, Na in C-S-H K OH - Na ph (36 days) 11.3 Al Ca K Na OH S Si.5 S Ca Time (days) Al Si Saturation indices 1 oversaturation: precipitation possible eff saturationindex 1 IAP log n K S n number of ions portlandite undersaturation: dissolution time (days) 45

46 cm 3 /1 g cm 3 /1 g cement Modeling Hydration gypsum strätlingite FH C 3 (F,A)S.84 H calcite monocarbonate hydrotalcite calcite hydrotalcite accelerator portlandite silica fume clinker C-(A-)S-H C-(Al)-S-H Al/Si = E Time (days) Influence of SiO 2 Slow silica fume dissolution! monocarbonate C hydrotalcite 3 FS.84 H 4.32 portlandite gypsum calcite 3 2 C-(A-)S-H 1 92 PC SiO years 3% g SiO 2 / SiO 1 g 2 4% SiO 2 46

47 volume cm 3 /1g blended cement Conclusion: PC - SCM Composition of hydrates Composition of SCM Reactivity of SCM -> depends on mineral assemblage, ph, -> challenge to measure Composition of hydrates change with time C-S-H: Ca/Si, Al and alkali uptake -> generic thermodynamic models for Al-alkali-C-S-H needed No portlandite, no monocarbonate, possibly strätlingite formation Thermodynamic modeling Quantitative prediction of hydrates Complementary to experimental studies Hydration PC - fly ash (35%) C C 3 A 4 AF C 2 S C 3 S FA limestone hydrotalcite De Weerdt ea 211, CCR 41 time [days] C-S-H CH monocarbonate hemicarbonate monosulpha FA C3S C2S C3A C4AF C-S-H Portlan ettrini gypsum calcite monos brucite hydrota strätli monoc hemica solutio 47

48 phase / cm 3 / 1 g dry cement Alternative cements: reaction of C$A pore solution straetlingite 6 amorphous Al(OH) 3 monosulfate 4 2 anhydrite ye'elimite belite inert Winnefeld, Lothenbach 21: Cem. Concr. Res. 4, time / h LINKS Experimental Porosity and permeability Thermodynamic approach Physical properties kinetic Mineralogy and microstructure 96 48

49 Thermodynamic modelling Interpretation of experimental results Interpolation Easy parameter variations: calcite, composition, Understanding Composition <-> hydrate assemblage Thermodynamic modelling: limits Thermodynamic data Small differences in data -> other solids stable Gaps in database: siliceous hydrogarnets, hydrotalcites, Fe-hydrates, Al-K-Na uptake in C-S-H, Kinetics: some phases are metastable C-S-H metastable Hydrated cement thermodynamically unstable 49

50 cm 3 /1g unhydrated cement C 3 S C-S-H SiO 2 (am) Monosulfate Portlandite Calcite (+MgCO 3 ) Ht completely hydrated cement Hemic Equilibrated with atmosphere + 5 g CO 2 (4.4 m 3 air) unhydrated cement CsH 2.. C 4 AF C 3 A C 2 S Very long time AH 3 FH 3 gypsum Future challenges Modelling of blended PC and non PC systems hydrates microstructure? solution dissolution/precipitation kinetic Thermodynamic data Ongoing work C-S-H: K, Na, Al, SO 3, Cl, uptake Fe-phases: AFt, AFm, hydrogarnet,? C 3 ASH 4 : kinetic? M-S-H, zeolites, Accuracy of thermodynamic data International validation Input from molecular modelling 1 5

51 cm 3 /1 g cement Questions? pore solution gypsum C 4 AF C 3 A C2 S C 3 S Hydration of mortar (w/c =.5) C-S-H monosulfate portlandite hydration time [days] barbara.lothenbach@empa.ch hemicarbonate hydrotalcite 11 Thermodynamic data, tutorials and link to modelling software can be downloaded from 51