View
30
Download
5
Category
Preview:
DESCRIPTION
Quantification of mineral admixtures on cement by Rietveld method. Luciano Gobbo, PhD, Geosciences Intitute - USP Luciano.gobbo@panalytical.com. X ray Diffraction. Bragg’s law: n = 2d sin . Difractogram. 100 % intensity. Angular positions. Relative intensities. Crystalline. - PowerPoint PPT Presentation
Citation preview
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
Recommended