3492
Conversion of Mine Tailings into Cementitious
Materials—A Conceptual Framework
Jannie S.J. van Deventer
Zeobond Pty Ltd
ABSTRACT: The mining industry aims to reduce its environmental footprint. Likewise, the cement industry
as a large emitter of CO2 is replacing clinker with supplementary cementitious materials (SCM). Mineral
processing circuits could recover sand for use in concrete, hence minimizing tailings. Dewatered slimes, preferably
when combined with a calcium source at a mine site, can be converted into reactive SCM. Alternatively,
aluminosilicates like clay and slimes can be fused with a calcium source in modular supersonic shockwave
reactors coupled with shock quenching to produce Portland cement. The reactor modules can produce different
cementitious materials that can be combined in different proportions to give low-CO2 types of cement suitable
for construction or use at a mine site. The incumbent process of clinker formation in a rotary kiln is not capable
of performing these conversions. A new pathway is proposed here to integrate the value chains of mining and
construction materials. The construction industry must shift from prescriptive standards to a framework of
performance-based standards based on universal durability testing.
COMMON FEATURES BETWEEN THE
MINING AND CEMENT INDUSTRIES
It is not the aim of this paper to debate whether anthropo-
genic CO2 is a controlling factor in climate change. Societal
pressure to reduce CO2 emissions will continue to influence
government policy and investment decisions. Demand for
renewable energy and electrification will increase demand
for metals to the extent that the transition to a green econ-
omy may become geologically constrained. Already, the
global metals and mining industry contributes 8 to 10%
of the global CO2 emissions (Azadi et al. 2020 Cox et al.
2022). It appears that society fails to understand the inter-
relationship between energy policy and metals production.
Declining grades of existing deposits also increase
energy consumption to maintain the same production of
metals. For example, declining grades in copper mining in
Chile from 2001 to 2017 resulted in a 130% increase in
fuel consumption and a 32% increase in electricity con-
sumption per unit of mined copper (Azadi et al. 2020). The
mining industry has a fractured position on carbon pric-
ing and the adoption of CO2 reduction targets (Cox et al.
2022). In this regard, Table 1 shows that the cement and
concrete industry has several features in common with the
mining and metals industry.
About two-thirds of the CO2 emissions of the cement
industry are caused by the decarbonization of limestone to
produce clinker and one-third is related to fuel consump-
tion (Ben Haha et al. 2023). With average emissions of
838 kg CO2 per ton clinker for modern plants (Schneider
et al 2023), there is an incentive for the cement industry to
reduce CO2 emissions, which is largely achieved by replac-
ing clinker with supplementary cementitious materials
(SCM). The cement industry does not intend to change
clinker production, except for adding carbon capture and
storage (CCS) to rotary kilns. This paper explains why
Conversion of Mine Tailings into Cementitious
Materials—A Conceptual Framework
Jannie S.J. van Deventer
Zeobond Pty Ltd
ABSTRACT: The mining industry aims to reduce its environmental footprint. Likewise, the cement industry
as a large emitter of CO2 is replacing clinker with supplementary cementitious materials (SCM). Mineral
processing circuits could recover sand for use in concrete, hence minimizing tailings. Dewatered slimes, preferably
when combined with a calcium source at a mine site, can be converted into reactive SCM. Alternatively,
aluminosilicates like clay and slimes can be fused with a calcium source in modular supersonic shockwave
reactors coupled with shock quenching to produce Portland cement. The reactor modules can produce different
cementitious materials that can be combined in different proportions to give low-CO2 types of cement suitable
for construction or use at a mine site. The incumbent process of clinker formation in a rotary kiln is not capable
of performing these conversions. A new pathway is proposed here to integrate the value chains of mining and
construction materials. The construction industry must shift from prescriptive standards to a framework of
performance-based standards based on universal durability testing.
COMMON FEATURES BETWEEN THE
MINING AND CEMENT INDUSTRIES
It is not the aim of this paper to debate whether anthropo-
genic CO2 is a controlling factor in climate change. Societal
pressure to reduce CO2 emissions will continue to influence
government policy and investment decisions. Demand for
renewable energy and electrification will increase demand
for metals to the extent that the transition to a green econ-
omy may become geologically constrained. Already, the
global metals and mining industry contributes 8 to 10%
of the global CO2 emissions (Azadi et al. 2020 Cox et al.
2022). It appears that society fails to understand the inter-
relationship between energy policy and metals production.
Declining grades of existing deposits also increase
energy consumption to maintain the same production of
metals. For example, declining grades in copper mining in
Chile from 2001 to 2017 resulted in a 130% increase in
fuel consumption and a 32% increase in electricity con-
sumption per unit of mined copper (Azadi et al. 2020). The
mining industry has a fractured position on carbon pric-
ing and the adoption of CO2 reduction targets (Cox et al.
2022). In this regard, Table 1 shows that the cement and
concrete industry has several features in common with the
mining and metals industry.
About two-thirds of the CO2 emissions of the cement
industry are caused by the decarbonization of limestone to
produce clinker and one-third is related to fuel consump-
tion (Ben Haha et al. 2023). With average emissions of
838 kg CO2 per ton clinker for modern plants (Schneider
et al 2023), there is an incentive for the cement industry to
reduce CO2 emissions, which is largely achieved by replac-
ing clinker with supplementary cementitious materials
(SCM). The cement industry does not intend to change
clinker production, except for adding carbon capture and
storage (CCS) to rotary kilns. This paper explains why