quantification of mineral admixtures on cement by rietveld method

Quantification of mineral admixtures on cement by Rietveld method

Luciano Gobbo, PhD, Geosciences Intitute - USPLuciano.gobbo@panalytical.com

Bragg’s law:

n=2dsin

X ray Diffraction

20 30 40 50 60 70 802Theta (°)

0

10000

40000

90000

160000

Inte

nsity

(co

unts

)

Angular positions

Relative intensities

100 % intensity

Difractogram

Crystalline

Amorphous

1. Mechanical properties and performance characteristics of clinkers and cements are primarily determined by:

….not elemental concentration.

• structure, • composition, and • distribution of crystalline (mineral) phases…

• Alite• Belite• C3A• C4AF• CaO• MgO ...

XRDXRD

Why XRD?

Cement compound Formula Cement property

Alite C3S Strengh (initial)

Belite C2S Strengh (28 days)

Aluminate C3A Setting time

Ferrite C4AF Sulphate attack / not in white cement

Mayenite C12A7 Faster setting time

Arcanite K2SO4 Initial strengh + fast setting time, lower final strengh

Langbeinite K2SO4.2CaSO4 Initial strengh + fast setting time, lower final strengh

Free lime CaO Expansive hydration [CaO + H2O Ca(OH)2]

Periclase MgO Expansive hydration [MgO + H2O Mg(OH)2]

Calcite / Dolomite (Mg,Ca)CO3 Carbonatation

Gypsum CaSO4.2H2O Setting retarder

Bassanite CaSO4.1/2H2O False setting

Anhydrite CaSO4 Slow setting

Why XRD?

• Bogue Method

• Microscopy

• XRD - Rietveld

Clinker quantification

• Developed in 1929 4 Elements (adapted later)

• Alite 3-4% 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+

Bogue

Microscopy

Microscopy

• Fast

• Reproducible

• Possible to quantify Types of Alite, Belite

Cubic and Orthorhombic C3A

Alkaline sulphates

Periclase, Free lime, Ca(OH)2

XRD

com

pres

sive

stre

ngth

[N/m

m²]

20

40

60

80

0

0

7 28 90 180 350Time [days]

C S3

C S2

C A3

C AF4

com

pres

sive

stre

ngth

[N/m

m²]

20

40

60

80

0

0

7 28 90 180 350Time [days]

C S3

C S2

C A3

C AF4

0

10

20

30

40

50

60

70

80

90

Zeitachse

%

59

60

61

62

63

64

65

66

67

68

69

70

MP

a

C3S Bogue

C3S Rietveld

N28

XRD – real case

XRD – real case

Rietveld (1969) developed a means to refine crystal 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.

XRD – Rietveld Method

Dr Hugo Rietveld – Halle, Germany (2009)

1. For each phase present a diffraction pattern is calculated

2. For all phases a total pattern is generated

3. The difference between observed and calculated patterns is minimized by varying parameters in the model through a least squares process

The Rietveld method uses all peaks and the complete profile for the analysis:

The Rietveld method is the best practical way to quantify the phases in clinker/cement

Quantitative analysis of clinker and cement: RietveldQuantitative analysis of clinker and cement: Rietveld

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...)

XRD – Rietveld Method

1st Step – Data Collection

2nd Step – Calculated diffractogram insertion

3rd Step – Start Refinement of each parameter (scale factor, zero shift, unit cell, profile (Gauss/Lorenz), assimetry, prefered orientation...)

XRD – Rietveld Method

Phase B

Phase B

Phase A

Phase A

Calculated area + corrections = phase amount

Phase A = 64%

Phase B = 36%

XRD – Rietveld Method

XRD – Rietveld Method

A

XRD – Rietveld Method

B

XRD – Rietveld Method

C

XRD – Rietveld Method

D

XRD – Rietveld Method

E

XRD – Rietveld Method

F

XRD – Rietveld Method

XRD – Rietveld Method

Final Result

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%

Fly ash Bottom Ash

Selected Fly ash

Amostra n Básica/Ácida % em massa de vidro (m)

CaO/SiO2 IH*

Alemanha IH** Brasil

S1 >1,64 Básica 87,3 1,17 1,27 1,84

S2 >1,64 Básica 88,7 1,16 1,27 1,82

S3 >1,64 Básica 89,0 1,19 1,28 1,85

S4 >1,64 Básica 90,1 1,15 1,26 1,82

S5 >1,64 Básica 90,2 1,14 1,25 1,81

S6 >1,64 Básica 90,8 1,10 1,22 1,77

S7 >1,64 Básica 93,9 1,21 1,25 1,78

S8 >1,64 Básica 99,2 1,22 1,26 1,77

S9 >1,64 Básica 99,2 1,28 1,30 1,82

S10 >1,64 Básica 94,9 1,26 1,32 1,78

S11 <1,62 Ácida 62,1 0,85 0,84 1,09

S12 <1,62 Ácida 69,4 0,86 0,84 1,10

S13 <1,62 Ácida 70,4 0,70 0,70 0,93

S14 <1,62 Ácida 53,3 0,69 0,69 0,93

S15 <1,62 Ácida 76,3 0,75 0,75 1,01

S16 <1,62 Ácida 61,8 0,60 0,63 0,84

S17 <1,62 Ácida 43,7 0,71 0,71 0,91

Selected Slag

Basic Slag Acid Slag

Selected Slag

Empyrean diffractometer used in the data collection

(Panalytical)• 10-70 ˚2θ

• 5 min• Cu anode

- Rietveld quantitative analysis with High Score Software from Panalytical

Results

Cement + Gypsum

y = 1,0592x

R2 = 0,99070

3

6

9

0 3 6 9

% Gipsita - Rietveld

% G

ipsi

ta

Cement + Limestone

y = 0,987x

R2 = 0,99620

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14

% de Calcário - Rietveld

% d

e C

alc

ári

o

Cement + Fly ash

Cement + 10-60% Fly ash

CalciteLiF

Fly ash variation

y = 0,9699x

R2 = 0,9919

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

% Cinza Volante CV1 inserida

% C

inza

Vo

lan

te -

Rie

tve

ld

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

F1-CV10i

F1-CV20i

F1-CV30i

F1-CV40i

F1-CV50i

F1-CV60i

Cinza Volante

Clínquer

Calcário

Fosfogesso

Cement + Fly ash

Slag variation

Cement + 10-60% Slag

LiF

Slag variation

y = 1,0329x

R2 = 0,9955

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

% Escória F2 inserida

% E

scó

ria

-Rie

tve

ld

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

F3-E20i

F3-E40i

F3-E60i

Escória

Clínquer

Calcário

Fosfogesso

Cement + Slag

30 40 50 60 70 80 90 100

30

40

50

60

70

80

90

100

1:1 +/-2.0% error

am

orp

hous

port

ion c

alc

ula

ted (

wt.

-%)

glass expected weight (wt.-%)

Blended cements:amorphous and crystalline to ±2 wt%

Mixtures of crystallineand amorphous phases

Every mixture wasprepared and measured ten times

Amorphous 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.-%

Phases error

Problems in Sample Preparation

Oriented Randomly

(002)(002)

Why/When?

• Pressing

• Flat crystals

• Alite

• Gypsum

• Portlandite

• Clay minerals

• Mullite

Sample preparation

15s30s60s120 s180 s

AliteCommon to gypsum

Sample preparation

Conclusion

- XRD-Rietveld analysis is a fast and reproducible method

- % of all clinker phases (different types of C3A and alkaline sulphates)

- Quantification of amorphous in cement – useful cements with pozzolanic materials

- Higher correlation with cement between quantitative results and cement properties

Thank you! Gracias!

Questions:luciano.gobbo@panalytical.com