Latest news on the application of the Rietveld method to quality control of cements

Transcription

1 Latest news on the application of the Rietveld method to quality control of cements Ángeles G. De la Torre University of Málaga, Spain

2 Outline Rietveld method: History and theory Parameters controlled by XRD & Rietveld Control-files/turn-key Sulphate carriers: gypsum, bassanite or anhydrite Additions (filler, pozzolans, etc.) Cement storage: syngenite Clinkering process XRD & Rietveld: more knowledge Conclusions Alternative Fuels Blockage of preheaters Raw materials: Gypsum

3 History 1967 Rietveld: neutron diffraction for structure refinement After that: X-ray diffraction and also: quantitative phase analysis Dr. Hugo M. Rietveld Important goals: Development of fast X-ray detectors Development of powerful computers

4 X-Rays X-Rays Why is XRD important for Clinker and Cement? Cement is specified for its properties The phases (not the elemental composition) determine the mechanical properties The better control of the clinker phases leads directly to the expected properties Knowledge of the possible properties leads to a better control in cement blending What does the Rietveld method consist on? Comparison of a calculated and an experimental XRD pattern Difference curve

5 Parameters controlled by XRD & Rietveld Central laboratories for research support Servicios Centrales de apoyo a la investigación (SCAI) XRD laboratory Laboratorio de Difracción de rayos-x XRD specialized analyst Research fellow Control-files/turn-key Special situations

6 Parameters controlled by XRD & Rietveld Control-files/turn-key Work prior to installation of control-file(s): Measure 4-6 your diffractometer, (mandatory) Send some grams of additions (filler, pozzolan, slag, ), (optional) It is completely automated 80 Software previously adapted by experts Wt % C3S C2S C4AF C3A CaO MgO K2SO4 20 K3Na(SO4)2 IN Rietveld Sample

7 XRD & Rietveld Cem1 Cem2 C 3 S/ % 62.1(4) 52.2(4) Parameters controlled by XRD & Rietveld Sulphate carriers: gypsum, bassanite or anhydrite C 2 S / % 12.7(6) 22.5(4) C 4 AF / % 11.4(3) 10.9(2) C 3 A/ % 5.0(2) 5.2(2) aftitalite/ % 1.4(2) 0.9(1) Gypsum/ % - 0.7(1) Bassanite/% 6.26(3) 3.9(1) LSF Blaine / cm 2 g -1 R1 / Nm -2 R2 / Nm -2 R3 / Nm -2 R7 / Nm -2 R28 / Nm -2 Setting time / min Cem Cem Gypsum Bassanite anhydrite The only way to control and understand setting Dehydration of gypsum to bassanite/anhydrite on milling process Or Natural raw material Control-files/turn-key

8 Parameters controlled by XRD & Rietveld Additions (filler, pozzolans, etc.) Filler (crystalline material) Pozzolan (mixture of amorphous and crystalline material) L CEM II B-L P P CEM II B-P L Control-files/turn-key

9 Parameters controlled by XRD & Rietveld Cement storage: syngenite K 2 Ca(SO 4 ) 2 (H 2 O) From: Arcanite + calcium sulphates = syngenite (high humidity) Control-files/turn-key

10 Parameters controlled by XRD & Rietveld Clinkering process: From the milling point of view XRD & Rietveld Similar LSF High amounts of C 3 S, no free lime High mechanical strengths expected at early ages Clink-2 and Clink-3 OK BUT Clink-1 develops low mechanical strengths at early ages???

11 XRD & Rietveld Parameters controlled by XRD & Rietveld Clinkering process: milling company Clink-2 and Clink-3 OK BUT Clink-1 develops low mechanical strengths at early ages??? The clinker was not properly cooled (slowly) and likely overheated. Only XRD C 3 S in clink-1 presents high crystallinity and larger particles The split is shown Thus, C 3 S is less reactive Why is more crystalline?? Why their particles are bigger?

12 XRD & Rietveld: more knowledge Alternative Fuels % of alternative fuels used in Europe (2003) C 3 S basanita C 3 S C 3 S C 2 S ZnO C 3 S C 3 A C 4 AF C 3 S ZnO C 3 S calcita Ca 3 SiO 5 (C 3 S) Ca 2 SiO 4 (C 2 S) Ca 3 Al 2 O 6 (C 3 A) Ca 2 AlFeO 5 (C 4 AF) CaSO 4 1/2H 2 O (bassanite) CaSO 4 (anhydrite) SiO 2 (quartz) CaCO 3 (calcite) CaMg(CO 3 ) 2 (dolomite) ZnO (zincite) Phase CEM ± ± ± ± ± ± ± ± ± 0.2* 1.1 ± 0.1 CEM ± ± ± ± ± ± ± 0.1* 7.3 ± ±

13 XRD & Rietveld: more knowledge Blockage of preheaters Phases Ca 5 (SiO 4 ) 2 CO 3 (spurrite) 22.1(4) 16.6(5) Ca 5 (SiO 4 ) 2 SO 4 (ternesite (sulfo-spurrite)) 2.7(2) 36.5(4) 21.4(4) CaSO 4 1.3(1) 0.9(1) 2.9(2) 1 Ca 4 Al 6 O 12 (SO 4 ) (Yeelimite) 1.1(1) - - Ca 11 (SiO 4 ) 4 O 2 S (jasmundite) 3.4(2) 7.3(3) 3.7(2) CaS - 1.9(1) 2.7(1) -Ca 2 SiO (4) 11.1(3) 31.6(4) Ca 4 Al 2 Fe 2 O (2) 5.7(2) 6.4(2) Ca 3 Al 2 O 6 1.1(2) - - CaO 7.4(1) - 1.1(1) Ca 12 Al 14 O (2) 9.0(2) 8.5(2) CaCO 3 7.5(3) 2.7(1) 1.5(2) MgO SiO 2 (coesite) SO 3 cycle? Cl -? 1.6(1) 1.9(1) 1.2(1) 1.6(2) 1.4(1) 2.1(2) C 2 S Ternesite Jasmundite C 2 S C2 S C 2 S Spurrite A Challenge

14 XRD & Rietveld: more knowledge Raw materials: Gypsum A sample of Gypsum which was not suitable for white cements Why?? Celestite gives color to the gypsum

15 Conclusions XRD & Rietveld for quality control of clinker and cements Find correlations between mineralogical compositions and performances XRD & external specialised laboratories for special situations X-Rays X-Rays Thanks to remaining authors Miguel A. G. Aranda Laura León-Reina Héctor Alonso-Llorente