ENCYCLOPÉDIE DE LA RECHERCHE SUR L’ALUMINIUM AU QUÉBEC 2013 | Page 22

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PRODUCTION D’ALUMINIUM
ALUMINIUM PRODUCTION
ÉTUDE DES PROPRIÉTÉS MÉCANIQUES ET DU COMPORTEMENT
VISCOÉLASTIQUE DE LA PÂTE DE BRUSQUE
STUDY OF RAMMING PASTE’S MECHANICAL PROPERTIES
AND VISCO-ELASTIC BEHAVIOUR
Pierre-Olivier St-Arnaud1, Donald Picard1,2, Houshang Alamdari1,2,
Donald Ziegler3, Mario Fafard1
1 NSERC/Alcoa Industrial Research Chair MACE3 and Aluminium Research Centre – REGAL
Université Laval, Québec, QC, G1V 0A6, Canada
Department of Mining, Metallurgical and Materials Engineering, 1065 avenue de la Médecine
Université Laval, Québec, QC, G1V 0A6, Canada
3 Alcoa Primary Product, Alcoa Technical Center, 100 Technical Drive, Alcoa Center, 15069-0001, PA, USA
2

1. INTRODUCTION

5. MASS LOSS

 To fill and seal the voids between the cathode
blocks and between the sidewall arrangement and
the cathode bottom lining (joints/peripheral seam)
 To absorb the thermal expansion from the
prebaked cathode blocks, while the paste goes
through various transformations during preheating

2. PROBLEMATIC
σ = cst

εa

High
temperature

σ = cst

εa
εr
εr = ?

Fig. 2: Mapping hypothesis for the
extrapolation of the radial strain at
elevated temperatures using
measurements at room temperature
(reference state)

Thermo-mechanical properties of the
ramming paste depend on its baking
temperature
Creep occurs while the paste is being
compressed by the thermal expansion
of the cathode blocks
It is difficult to perform 3D mechanical
characterization at high temperature
(oxidation, devices limitations, etc.)
Data are necessary to feed threedimensional creep model where radial
strain measurements are required.
Hypothesis : the relationship between
axial and radial strain for a given
baking temperature holds for all
temperatures below the baking one

12

10

8

1000 °C
750 °C
560 °C

6

500 °C
460 °C

4

350 °C
250 °C

2

0

0

200

400
600
Temperature [°C]

800

1000

Fig. 8: Mass loss in percentage as a function of baking temperature of ramming paste

6. COMPRESSION TESTS
COMPRESSIVE STRENGTH
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Fig. 3: Creep test on ramming paste
baked at 200°C (Orangi et al., New
Observations in Creep Behaviour of
Ramming Paste in Aluminium Electrolysis
Cell, 2011)

3. OBJECTIVES

8

18
16
14

1000 °C

12

750 °C

10

560 °C

8

500 °C

6

460 °C
350 °C

4

250 °C

2
0
200

400
600
800
Baking temperature [°C]

1000

Fig. 9: Compressive strength of the baked samples related to their baking
temperatures

To elaborate a new compaction method for large size samples in order to increases
the signal amplitude for radial strain.
2. To determine the Young’s modulus and the Poisson’s ratio of the ramming paste at
room temperature for different baking temperatures.
3. To perform creep tests at room temperature for different baking temperatures.


YOUNG’S MODULUS

7

Young's Modulus [GPa]

Room
temperature

Compressive Strength [MPa]

Fig.1: Aluminium Electrolysis Cell (D’Amours, Développement
des lois constitutives thermomécaniques pour les matériaux à
base de carbone lors du préchauffage d’une cuve d’électrolyse,
2004)

 Poor conditions of rammed part may lead to
infiltration of liquid bath and molten aluminium in
the lining, often resulting in early pot failure

Volatilization of binder’s
products starts early in
the baking process and
reaches its maximum
rate around 450 C.
Then dehydrogenation
occurs
until
the
solidification
of
the
binder (carbonization)
is complete. The mass
loss reaches a plateau
during this step.
As it shrinks, ramming
paste develops more
porosity
between
500 C and 1000 C.

Mass loss [%]

Purposes of ramming paste

6
5
4
3
2
1
0
200

400
600
800
Baking temperature [°C]

1000

Fig. 10: Young’s modulus of the baked samples related to their baking
temperatures

The baking temperature has a strong influence on the compressive strength.
Carbonization (above 500 C) affects the samples as they get more tough and
less deformable with the rise in temperature. Young’s modulus values follow a
similar trend. Variations within the 350 C results could be attributed to the
unfinished volatilization process, which differs from on sample to another.
Poisson’s ratio : initially near 0.5 (green paste), decreases quickly to
approximately 0.20 (500 C), and finishes at nearly 0.17 (1000 C)

Compaction method

Pierre-Olivier St-Arnaud
Mario Fafard
Chaire de recherche industrielle
CRSNG/Alcoa MACE3,
Centre de recherche
sur l’aluminium - REGAL,
Université Laval
Donald Picard
Houshang Alamdari
Chaire de recherche industrielle
CRSNG/Alcoa MACE3,
Centre de recherche
sur l’aluminium - REGAL,
Département de génie des
mines, de la métallurgie et des
matériaux, Université Laval

4. METHODOLOGY

Sample dimensions : 101.6 mm (4 in) in
diameter and 203.2 mm (8 in) in height
Compaction apparatus : Mechanical rammer
(based on ASTM D1557-09 standard)
Fig. 4: Compaction pattern
Circular pattern with a 50.8 mm
(ASTM D1557-09)
(2 in) diameter rammer
Free fall : 457.2 mm (18 in)
Rammer weight : 2.49 kg (5.5 lb)
11 layers, 14 impacts/layer (aimed
density of 1.61 g/cm3)
Apparent density measured according
to ASTM D5502-00 standard
Fig. 5: Volume measurement (ASTM D5502-00)

7. CREEP TESTS
AXIAL SPECIFIC CREEP

RADIAL SPECIFIC CREEP

Fig. 6: Proctor Mechanical Rammer

Sample baking
Heating program : ISO 20202:2004
Baked in a steel box, samples are covered with coke (to
avoid oxidati ۊB