Technology Roadmap Low-Carbon Transition in the Cement Industry

Figure 16: Process CO
2
 emissions generation intensity for selected
cement binding materials
Notes: BCSA = belite calcium sulphoaluminate, CACS = carbonation of calcium silicates, CSA = calcium sulphoaluminate, MOMS 
= magnesium oxide derived from magnesium silicates, PC = Portland cement. PC clinker mainly contains 63% alite, 15% belite, 
8% tricalcium aluminate and 9% tetracalcium alumino-ferrite. Belite clinker mainly contains 62% belite, 16% alite, 8% tricalcium 
aluminate and 9% tetracalcium alumino-ferrite. CSA clinker mainly contains 47.5% ye’elimite, 23.9% belite, 12.9% wollastonite and 
8.6% tetracalcium alumino-ferrite. BCSA clinker mainly contains 46% belite, 35% ye’elimite and 17% tetracalcium alumino-ferrite. 
Commercial compositions of CACS clinker are not currently available. The CACS clinker in this assessment is considered to primarily 
consist of wollastonite, but commercial composition is likely different, and possibly higher in process CO
2
emissions. Process CO
2
emissions generated in CACS clinker making are, in principle, re-absorbed during the curing process. MOMS are considered to be 
sourced from magnesium silicate rocks. Given the wide range of mix designs, sources and doses, it is not possible to provide a single 
value or even a well-defined range to describe the CO
2
footprint of alkali-activated binders. The figure above shows two possible 
extreme examples ranging from 97% to 10% CO
2
savings compared to PC.
Sources: Quillin (2010), 
Calcium Sulfoaluminate Cements: CO
2
 Reduction, Concrete Properties and Applications
; UNEP (2016), 
Eco-efficient 
Cements: Potential, Economically Viable Solutions for a Low-CO
2
, Cement-based Materials Industry
; Gartner and Sui (2017), 
Alternative 
Cement Clinkers
.
0
100
200
300
400
500
600
PC
clinker
Belite
clinker
CSA
clinker
BCSA
clinker
CACS
clinker
MOMS
clinker
Alkali-
activated
binders
kg
p
ro
ce
ss
C
O
/t
b
in
d
in
g
m
a
te
ri
al
2
Potential comparative
process CO savings
2
Process CO intensity
2
Commercial
Demonstration-pilot
phase
R&D phase

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