XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3493
rotary kilns are inhibiting innovation and proposes an alter-
native for the production of low-CO2 type of cement.
At present, coal fly ash (CFA) and ground granulated
blast furnace slag (GBFS) constitute the majority of SCM,
with calcined clay (CC) and finely ground limestone (GL)
being used increasingly as well. As a result of decarboniza-
tion, CFA and GBFS are in short supply and absent in sev-
eral markets. Therefore, there is a need for new sources of
SCM and the production of synthetic SCM (Snellings et al.
2023). The increased use of SCM in concrete is challeng-
ing, as the reactivity of SCM is a function of amorphous
content and usually, the reactivity of SCM is substantially
lower than that of clinker (Snellings et al. 2023). Activating
agents, as well as more precise control over size distribution,
can be used to enhance the hydration of SCM (Ben Haha
et al. 2023), which leads to challenges in dispersion and
plasticizing of the wet concrete (Flatt et al. 2023).
Table 1 suggests that there in an opportunity to inte-
grate the needs of the mineral and cement industries
through utilization of tailings, which will reduce waste and
CO2 emissions. This paper develops a conceptual frame-
work for such collaboration. The concepts presented here
are based on the extensive experience of the author in both
the minerals industry and construction materials.
TAILINGS SAND AS CONCRETE
AGGREGATES
Several reviews have been published recently on the repur-
posing of mine tailings, especially for use as aggregate in
concrete (Sigvardsen et al. 2018 Gou et al. 2019 Paiva et
al. 2019 Adiguzel et al. 2022 He et al. 2022 Ikotun et al.
2022 Qaidi et al. 2022). The popularity of this approach
stems from societal pressure to minimize the environmental
impact of mining and increased academic focus on the cir-
cular economy. As summarized in Table 2, commercial suc-
cess has been limited. While Beylot et al. (2022) provide a
review of Life-Cycle Analysis (LCA) on tailings utilization,
the complexity of LCA and Environmental Product
Declaration (EPD) in a commercial environment is less
appreciated.
Quarries for supplying sand and aggregate to the con-
crete industry are valuable assets if located near population
centers because communities resist permitting of new quar-
ries, even in remote areas. Moreover, the concrete industry
requires sand and aggregate with tightly controlled chemi-
cal and physical properties. Increasingly, sand and aggregate
recycled from demolition waste are being used, but they
Table 2. Commercial obstacles to adoption of low-CO
2 cement and concrete from tailings
• Prescriptive instead of performance-based standards
• Transport cost from remote mines to urban centers
• Toxic elements in tailings are prohibited from use in
concrete
• Slimes in tailings sand have deleterious effect on concrete
• Perception that tailings are toxic, even when toxic elements
have been removed
• Legal liability for disturbing old tailings incentivizes use of
fresh tailings
• Complexity of LCA and EPD for use of tailings in concrete
Table 1. Common features between the mining and cement industries
Feature Mining and Metals Cement and Concrete
Energy-intensive Yes Yes
Bulk materials handling Yes Yes
Contribution to global CO
2 emissions 8–10% (Azadi et al., 2020
Cox et al., 2022)
8% (Flatt et al., 2023)
Societal pressure to reduce CO
2 emissions Yes Yes
Fractured position on CO2 pricing and
adoption of CO2 reduction targets
Yes Yes
Constrained resources Grades of mineral deposits
are declining
Building sand, aggregate and
SCM are in short supply
Sand from tailings requires collaboration Processing circuits require
modification
Concrete mix designs and
admixtures require modification
Utilization of SCM Tailings hold potential for
CC and GL
Constrained supply of CFA and
GBFS
Modular reactors to produce synthetic SCM
and cement
Use in remote locations
will reduce cost
Flexibility of production will
reduce cost
rotary kilns are inhibiting innovation and proposes an alter-
native for the production of low-CO2 type of cement.
At present, coal fly ash (CFA) and ground granulated
blast furnace slag (GBFS) constitute the majority of SCM,
with calcined clay (CC) and finely ground limestone (GL)
being used increasingly as well. As a result of decarboniza-
tion, CFA and GBFS are in short supply and absent in sev-
eral markets. Therefore, there is a need for new sources of
SCM and the production of synthetic SCM (Snellings et al.
2023). The increased use of SCM in concrete is challeng-
ing, as the reactivity of SCM is a function of amorphous
content and usually, the reactivity of SCM is substantially
lower than that of clinker (Snellings et al. 2023). Activating
agents, as well as more precise control over size distribution,
can be used to enhance the hydration of SCM (Ben Haha
et al. 2023), which leads to challenges in dispersion and
plasticizing of the wet concrete (Flatt et al. 2023).
Table 1 suggests that there in an opportunity to inte-
grate the needs of the mineral and cement industries
through utilization of tailings, which will reduce waste and
CO2 emissions. This paper develops a conceptual frame-
work for such collaboration. The concepts presented here
are based on the extensive experience of the author in both
the minerals industry and construction materials.
TAILINGS SAND AS CONCRETE
AGGREGATES
Several reviews have been published recently on the repur-
posing of mine tailings, especially for use as aggregate in
concrete (Sigvardsen et al. 2018 Gou et al. 2019 Paiva et
al. 2019 Adiguzel et al. 2022 He et al. 2022 Ikotun et al.
2022 Qaidi et al. 2022). The popularity of this approach
stems from societal pressure to minimize the environmental
impact of mining and increased academic focus on the cir-
cular economy. As summarized in Table 2, commercial suc-
cess has been limited. While Beylot et al. (2022) provide a
review of Life-Cycle Analysis (LCA) on tailings utilization,
the complexity of LCA and Environmental Product
Declaration (EPD) in a commercial environment is less
appreciated.
Quarries for supplying sand and aggregate to the con-
crete industry are valuable assets if located near population
centers because communities resist permitting of new quar-
ries, even in remote areas. Moreover, the concrete industry
requires sand and aggregate with tightly controlled chemi-
cal and physical properties. Increasingly, sand and aggregate
recycled from demolition waste are being used, but they
Table 2. Commercial obstacles to adoption of low-CO
2 cement and concrete from tailings
• Prescriptive instead of performance-based standards
• Transport cost from remote mines to urban centers
• Toxic elements in tailings are prohibited from use in
concrete
• Slimes in tailings sand have deleterious effect on concrete
• Perception that tailings are toxic, even when toxic elements
have been removed
• Legal liability for disturbing old tailings incentivizes use of
fresh tailings
• Complexity of LCA and EPD for use of tailings in concrete
Table 1. Common features between the mining and cement industries
Feature Mining and Metals Cement and Concrete
Energy-intensive Yes Yes
Bulk materials handling Yes Yes
Contribution to global CO
2 emissions 8–10% (Azadi et al., 2020
Cox et al., 2022)
8% (Flatt et al., 2023)
Societal pressure to reduce CO
2 emissions Yes Yes
Fractured position on CO2 pricing and
adoption of CO2 reduction targets
Yes Yes
Constrained resources Grades of mineral deposits
are declining
Building sand, aggregate and
SCM are in short supply
Sand from tailings requires collaboration Processing circuits require
modification
Concrete mix designs and
admixtures require modification
Utilization of SCM Tailings hold potential for
CC and GL
Constrained supply of CFA and
GBFS
Modular reactors to produce synthetic SCM
and cement
Use in remote locations
will reduce cost
Flexibility of production will
reduce cost