XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3933
The end point of an in-situ compression experiment should
be determined by identifying the maximum breakage event,
with the aim of preventing any over-crushing.
In the XCT, changes in the projection image will
indicate at which force levels the measurement should
be conducted for each particle individually. The dataset
captured during the first breakage event will be used to
track the potential crack path under pressure and identify
locations where initial changes are evident based on the
microstructure.
Optical Examination of Fractured Slag Particles
Irrespective of the force-displacement curve patterns, visu-
ally examining the broken state of stressed slag particles
reveals four kinds of fragmentation (Figure 3):
A. The particle breaks into at least two fragments.
B. The particle remains intact, but a clear crack is visible.
C. Only a very small fragment is generated.
D. The particle appears visually intact, with only abra-
sion observable on the outer surface.
Given that fragments like (C) occurred only once and the
fragment make up less than 10% of the total particle mass,
according to Schubert (1975), it can be merged with (D) as
an intact particle.
The majority of slag particles either break into mul-
tiple fragments or exhibit a visible crack. There is no clear
correlation between fragmentation data and breakage force
(Figure 4). During the first breakage event, a small frag-
ment may break off instead of forming a crack, resulting in
lower breakage forces. This is particularly evident in case D,
where significantly lower breakage forces are observed for
both the first and maximum breakage events. This suggests
the breakage of fine fragments, resulting in curves with
minimal steep force-distance curve peaks and numerous
smaller local maxima, but without pronounced force drops.
In the in-situ compression of a slag particle, a median
breakage force of approximately 130 N (first breakage event)
is as a rapid and convenient force value for establishing the
force levels at which the experiment can be conducted. To
observe if there is any fracturing before reaching 130 N, a
measurement is undertaken at 80% of the breakage force
(around 100 N) even before a force drop occurs. The results
show that at 100 N still no changes within the particle can
be observed. To conduct scans closer to the breakage event,
80% of the breakage force proves as insufficient for brittle
materials and should include more force levels around the
estimated breakage force.
In comparing the changes observed in the particle
between the unloaded (i.e., F =5 N) and stressed states (F
=100 N), it has been demonstrated that for this slag sys-
tem, no additional measurements are required until a force
drop is detected.
The in-situ compression of a selected slag particle
follows an ideal progression in the force-distance curve
(Figure 5). The absence of deformations in µCT measure-
ments when no force drop occurs suggests that the ini-
tiation of the first debris particles results with the initial
breakage event. The breakage itself aligns with the compres-
sion stress applied to the particle, propagating from the top
to the bottom. It propagates both the matrix and the target
phase. Consequently, intergranular breakage or liberation
by detachment, as per Gaudin’s classification, can be ruled
Figure 3. Broken slag particle fragments. A complete breakage through the slag particle, B intact particle while the breakage
went through the center of the particle, C small fragment occurs, D crumbling on the surface of the slag particle without
breakage
The end point of an in-situ compression experiment should
be determined by identifying the maximum breakage event,
with the aim of preventing any over-crushing.
In the XCT, changes in the projection image will
indicate at which force levels the measurement should
be conducted for each particle individually. The dataset
captured during the first breakage event will be used to
track the potential crack path under pressure and identify
locations where initial changes are evident based on the
microstructure.
Optical Examination of Fractured Slag Particles
Irrespective of the force-displacement curve patterns, visu-
ally examining the broken state of stressed slag particles
reveals four kinds of fragmentation (Figure 3):
A. The particle breaks into at least two fragments.
B. The particle remains intact, but a clear crack is visible.
C. Only a very small fragment is generated.
D. The particle appears visually intact, with only abra-
sion observable on the outer surface.
Given that fragments like (C) occurred only once and the
fragment make up less than 10% of the total particle mass,
according to Schubert (1975), it can be merged with (D) as
an intact particle.
The majority of slag particles either break into mul-
tiple fragments or exhibit a visible crack. There is no clear
correlation between fragmentation data and breakage force
(Figure 4). During the first breakage event, a small frag-
ment may break off instead of forming a crack, resulting in
lower breakage forces. This is particularly evident in case D,
where significantly lower breakage forces are observed for
both the first and maximum breakage events. This suggests
the breakage of fine fragments, resulting in curves with
minimal steep force-distance curve peaks and numerous
smaller local maxima, but without pronounced force drops.
In the in-situ compression of a slag particle, a median
breakage force of approximately 130 N (first breakage event)
is as a rapid and convenient force value for establishing the
force levels at which the experiment can be conducted. To
observe if there is any fracturing before reaching 130 N, a
measurement is undertaken at 80% of the breakage force
(around 100 N) even before a force drop occurs. The results
show that at 100 N still no changes within the particle can
be observed. To conduct scans closer to the breakage event,
80% of the breakage force proves as insufficient for brittle
materials and should include more force levels around the
estimated breakage force.
In comparing the changes observed in the particle
between the unloaded (i.e., F =5 N) and stressed states (F
=100 N), it has been demonstrated that for this slag sys-
tem, no additional measurements are required until a force
drop is detected.
The in-situ compression of a selected slag particle
follows an ideal progression in the force-distance curve
(Figure 5). The absence of deformations in µCT measure-
ments when no force drop occurs suggests that the ini-
tiation of the first debris particles results with the initial
breakage event. The breakage itself aligns with the compres-
sion stress applied to the particle, propagating from the top
to the bottom. It propagates both the matrix and the target
phase. Consequently, intergranular breakage or liberation
by detachment, as per Gaudin’s classification, can be ruled
Figure 3. Broken slag particle fragments. A complete breakage through the slag particle, B intact particle while the breakage
went through the center of the particle, C small fragment occurs, D crumbling on the surface of the slag particle without
breakage