Quantification of mineral admixtures on cement by Rietveld method

2. Quantification of mineral admixtures on cement by Rietveld method Luciano Gobbo, PhD, Geosciences Intitute - USP Luciano.gobbo@panalytical.com

3. X ray Diffraction Bragg’s law: n=2dsin

4. Difractogram 100 % intensity Angular positions Relative intensities

5. Crystalline Amorphous

6. XRD Why XRD? • Mechanical properties and performance characteristics of clinkers and cements are primarily determined by: • structure, • composition, and • distribution of crystalline (mineral) phases… • Alite • Belite • C3A • C4AF • CaO • MgO • ... ….not elemental concentration.

7. Why XRD?

8. Clinker quantification • Bogue Method • Microscopy • XRD - Rietveld

9. Bogue • Developed in 1929 4 Elements (adapted later) • Alite3-4% substituent's - Na+, K+, Mg2+, Fe3+ (Ca2+) • - Al3+, P5+, S6+ (Si4+) • Belite 6% substituent's – K+, Na+, Mg2+ (Ca2+) • - Fe3+, Al3+, P5+, S6+ (Si4+) • Ferrite 10% substituent's – Mg2+, Si4+

10. Microscopy

11. Microscopy

12. XRD • Fast • Reproducible • Possible to quantify Types of Alite, Belite • Cubic and Orthorhombic C3A • Alkaline sulphates • Periclase, Free lime, Ca(OH)2

13. XRD – real case

14. XRD – real case

15. XRD – Rietveld Method Rietveld (1969) developed a means to refinecrystal structure information for powder (neutron) diffraction data by: • Using ‘initial’ crystal structures and • Minimizing the differences between calculated and measured profiles using a least squares approach with many variables for each phase. Dr Hugo Rietveld – Halle, Germany (2009)

16. The Rietveld method is the best practical way to quantify the phases in clinker/cement XRD – Rietveld Method The Rietveld method uses all peaks and the complete profile for the analysis: For each phase present a diffraction pattern is calculated For all phases a total pattern is generated The difference between observed and calculated patterns is minimized by varying parameters in the model through a least squares process Quantitative analysis of clinker and cement: Rietveld

17. XRD – Rietveld Method 1st Step – Data collection 2nd Step – Calculated pattern insertion 3rd Step – Start Refinement of each parameter (scale factor, zero shift, unit cell, profile (Gauss/Lorenz), assimetry, prefered orientation...)

18. XRD – Rietveld Method 1st Step – Data Collection 2nd Step – Calculated diffractogram insertion 3rdStep – Start Refinement of each parameter (scale factor, zero shift, unit cell, profile (Gauss/Lorenz), assimetry, prefered orientation...)

19. Phase A Phase B Phase A = 64% Phase A Phase B = 36% Phase B XRD – Rietveld Method Calculated area + corrections = phase amount

20. XRD – Rietveld Method A

21. XRD – Rietveld Method B

22. XRD – Rietveld Method C

23. XRD – Rietveld Method D

24. XRD – Rietveld Method E

25. XRD – Rietveld Method F

26. XRD – Rietveld Method

27. XRD – Rietveld Method Final Result

28. Metodology Cements prepared in laboratory with known amounts of: gypsum: 3, 6 and 9% limestone: 2, 5, 8, 10 and 12% fly ash: 10, 20, 30, 40, 50 and 60% slag: 20, 40 and 60%

29. Selected Fly ash Bottom Ash Fly ash

30. Selected Slag

31. Selected Slag Acid Slag Basic Slag

32. Empyrean diffractometer used in the data collection (Panalytical) • 10-70 ˚2θ • 5 min • Cu anode - Rietveld quantitative analysis with High Score Software from Panalytical

33. Results

34. Cement + Gypsum

35. Cement + Limestone

36. LiF Calcite Cement + Fly ash Cement + 10-60% Fly ash

37. Fly ash variation

38. Cement + Fly ash

39. Slag variation LiF Cement + 10-60% Slag

40. Slag variation

41. Cement + Slag

42. 100 90 80 70 60 50 40 30 30 40 50 60 70 80 90 100 Amorphous error Mixtures of crystalline and amorphous phases Every mixture was prepared and measured ten times amorphous portion calculated (wt.-%) 1:1 +/-2.0% error glass expected weight (wt.-%) Blended cements:amorphous and crystalline to ±2 wt%

43. Phases error • Alite 65 wt.-% ± 2 wt.-% • Belite 15 wt.-% ± 1.5 wt.-% • Ferrite 6 wt.-% ± 0.6 wt.-% • Aluminate 5 wt.-% ± 0.6 wt.-% • Lime 1 wt.-% ± 0.3 wt.-% • Periclase 1 wt.-% ± 0.3 wt.-% • Gypsum 2 wt.-% ± 0.4 wt.-% • Hemihydrate 1 wt.-% ± 0.3 wt.-% • Anhydrite 1 wt.-% ± 0.3 wt.-% • Calcite 1 wt.-% ± 0.3 wt.-% • Portlandite 1 wt.-% ± 0.3 wt.-% • Quartz 1 wt.-% ± 0.3 wt.-%

44. Problems in Sample Preparation

45. Sample preparation Why/When? Oriented Randomly • Pressing • Flat crystals • Alite • Gypsum • Portlandite (002) • Clay minerals (002) • Mullite

46. Sample preparation Common to gypsum Alite 15s 30s 60s 120 s 180 s

47. Conclusion • % of all clinker phases (different types of C3A and alkaline sulphates) • Quantification of amorphous in cement – useful cements with pozzolanic materials XRD-Rietveld analysis is a fast and reproducible method • Higher correlation with cement between quantitative results and cement properties

48. Thank you! Gracias!Questions: luciano.gobbo@panalytical.com