Presentation made at the 5th International Conference on AAC in Bydgoszcz (Poland - 14-17 Sept. 2011)

1. Impact of
quicklime reactivity and origin
on Autoclaved Aerated Concrete production
D. Lesueur (didier.lesueur@lhoist.com), F. Mücke,
H. Oeinck, U. Peter, C. Pust and F. Verhelst
Lhoist R&D / Rheinkalk / Lhoist

2. Outline
• Objective
• Materials
• Methods
• Results
• Conclusions
2

3. Outline
• Objective
• Materials
• Methods
• Results
• Conclusions
3

4. Objective
• Specifications on quicklime for AAC production are
essentially based on reactivity (EN 459-2)
90
80
Temperature (°C)
70
60
max
min
Quicklime
50
40
30
20
10
0
0
10
20
30
40
50
time (min)
• Is this enough?
4

5. Outline
• Objective
• Materials
• Methods
• Results
• Conclusions
5

6. Quicklimes
with various origin and reactivity
Calcination
LA1
LA2
LA3
IA1
IA2
IB
IC
Laboratory
Laboratory
Laboratory
Industrial
Industrial
Industrial
Industrial
Limestone
Origin
A
A
A
A
A
B
C
CaO
t60
wt.%
95.5
95.6
96.2
93.5
94.0
95.8
93.8
min
4.1
5.2
7.6
1.9
3.1
8.2
5.2
6

7. Quicklimes
with various origin and reactivity
80
temperature (°C)
70
LA1 4.1min
LA2 5.2min
LA3 7.6min
IA1 1.9min
IA2 3.1min
IB 8.2min
IC 5.2min
60
50
40
30
20
0
5
10
15
time (min)
20
25
30
7

8. 3 recipes covering
P2-0.35, P2 – 0.4 and P4 – 0.55 (EN 771-4)
Target density
Target compressive strength
Return Slurry
Quartz Sand
Cement
Lime
Anhydrite
Aluminium Paste
Water/Solid wt. ratio
Units
kg/m3
MPa
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
-
P2 – 0.35
300-350
>2
20
50
28
17
5
0.22
0.68
P2 – 0.4
350-400
>2
20
55
25
15
5
0.16
0.65
P4 – 0.55
500-550
>4
20
59
18
19
4
0.08
0.65
8

9. Outline
• Objective
• Materials
• Methods
• Results
• Conclusions
9

10. AAC production
and monitoring at laboratory scale
• Mix ingredients
¬
¬
¬
¬
Return slurry
Hot water (70°C)
Powders
Aluminium paste
900 Rpm Dissolver
Mixture
30L
Bucket
• Monitor green cake
expansion
¬ Height and temperature
¬ Final hardness
Datalogger
Ultrasound
sensor
Thermocouple
Green cake
10

11. AAC production
and monitoring at laboratory scale
• Autoclaving
¬ 225 l autoclave
¬ 2 hrs linear increase
¬ 6 hrs 11 bars / 190°C
• AAC testing
¬ density and
compressive strength
11

12. Outline
• Objective
• Materials
• Methods
• Results
• Conclusions
12

13. Quicklimes
with same origin and different reactivity
• Expansion monitoring P2 – 0.35
1.2
height / final height (-)
1.1
1.0
0.9
LA1 4.1min
LA2 5.2min
IA1 1.9min
IA2 3.1min
0.8
0.7
0.6
0.5
0.4
0
5
10
15
20
25
30
35
time (min)
40
45
50
55
60
13

14. Quicklimes
with same origin and different reactivity
• Expansion monitoring P2 – 0.35
height / final height (-)
1.10
1.05
1.00
LA1 4.1min
LA2 5.2min
IA1 1.9min
IA2 3.1min
0.95
0.90
10
15
20
time (min)
25
30
14

15. Quicklimes
with same origin and different reactivity
• Temperature P2 – 0.35
75
temperature (°C)
70
65
60
LA1 4.1min
LA2 5.2min
IA1 1.9min
IA2 3.1min
55
50
45
40
0
10
20
30
40
50
60
70
80
90
100
110
120
time (min)
15

16. Quicklimes
with same origin and different reactivity
• Expansion monitoring P2 – 0.35
1.2
height / final height (-)
1.1
1.0
0.9
LA2 5.2min
IA1 1.9min
IB 8.2min
IC 5.2min
0.8
0.7
0.6
0.5
0.4
0
5
10
15
20
25
30
35
40
45
50
55
60
time (min)
16

17. Quicklimes
with same origin and different reactivity
• Expansion monitoring P2 – 0.35
height / final height (-)
1.10
1.05
1.00
LA2 5.2min
IA1 1.9min
IB 8.2min
IC 5.2min
0.95
0.90
10
15
20
25
30
time (min)
17

18. Quicklimes
with different origin and reactivity
• Temperature P2 – 0.35
75
temperature (°C)
70
65
LA2 5.2min
IA1 1.9min
IB 8.2min
IC 5.2min
60
55
50
45
40
0
10
20
30
40
50
60
70
80
90
100
110
120
time (min)
18

19. Green cake:
Summary of findings
•
Thermal monitoring always matches expansion kinetics
•
With the studied recipes and methods, risk of overheating
was observed for P2 – 0.35 and highly reactive quicklimes
(expansion overshoot)
•
With the same limestone origin, the higher the reactivity, the
faster the green cake expansion
BUT with varying limestone origin, similar reactivities can lead
to different expansion kinetics
•
•
At the lab scale, green cake hardness essentially not affected
by quicklime properties
19

20. Quicklimes
with same origin and different reactivity
• Final AAC properties
compressive strength (MPa)
6
5
4
LA
IA
mean
3
2
1
250
300
350
400
450
500
550
density (kg/m3)
20

21. Quicklimes
with same origin and different reactivity
• Final AAC properties
compressive strength (MPa)
6
5
LA
IA
IB
IC
mean
4
3
2
1
250
300
350
400
450
500
550
density (kg/m3)
21

22. Final AAC:
Summary of findings
•
Final AAC properties were little affected by quicklime origin
•
Highly reactive quicklimes (expansion overshoot) gave low
compressive strength for the P2-0.35 recipe
•
IB quicklime seem to give consistently higher compressive
strength for a given density
¬ Tobermorite crystal size?
22

23. Outline
• Objective
• Materials
• Methods
• Results
• Conclusions
23

24. Conclusions
•
We developped a methodology to study quicklime effect on
AAC at the lab scale through
¬ Green cake monitoring
¬ AAC final properties
•
With the studied recipes and methods, risk of overheating
was observed for P2 – 0.35 and highly reactive quicklimes
(expansion overshoot) leading to low compressive strength
•
With the same limestone origin, the higher the reactivity, the
faster the green cake expansion
BUT varying limestone origin, similar reactivities can lead to
different expansion kinetics
•
24

25. Thank you for your attention