Technology Roadmap Low-Carbon Transition in the Cement Industry

Technology Roadmap
Low-Carbon Transition in the Cement Industry
Alternative binding cement 
materials at demonstration and 
pilot phases
z
Belite calcium sulphoaluminate (BCSA)
clinker 
is being investigated to circumvent the high raw 
material costs of CSA clinkers while delivering a 
CO
2
footprint advantage for ordinary concrete 
applications. This is achieved by increasing the 
proportion of belite and adding alumino-ferrite 
to CSA clinkers, thus delivering a clinker process 
CO
2
intensity 20-30% lower than that of PC 
(Gartner and Sui, 2017). Such BCSA clinkers can 
be produced with lower sintering temperatures 
and with 30-50% lower electricity demand for 
grinding as they are more friable (ECRA and CSI, 
2017). They are not commercially produced yet, 
and specific norms for this type of clinkers do not 
currently exist, with the exception of those BCSA 
clinker compositions that are within Chinese 
norms for CSA clinkers. This type of cement can 
be commercially applied in Europe for well-
defined applications, although specific local 
technical approval would be required (ECRA and 
CSI, 2017).
z
Cements based on 
carbonation of calcium 
silicates (CACS)
can sequester CO
2
as they cure. 
Therefore, even if they are based on similar raw 
materials to PC clinker, these types of cement can 
yield zero process CO
2
emissions in net terms, as 
the emissions would essentially be re-absorbed 
during the curing process. Thus, the main CO
2
emissions related to the manufacturing of CACS 
clinkers are related to the energy consumed in 
the kiln. The curing process occurs with relatively 
pure CO
2
at atmospheric pressure and controlled 
ventilation, temperature and relative humidity. 
This limits the application of CACS cements to 
precast products; in addition, they should not 
be too large in cross-section to ensure adequate 
curing. The fuel mix may be more restrictive 
than in normal PC practice, with the fuel sulphur 
content needing to be kept low and the use of 
wastes needing to be potentially limited. They 
are not expected to protect conventional steel 
reinforcement against corrosion, which therefore 
provides limited applicability to non-reinforced 
products or non-steel-reinforced products such as 
glass-fibre-reinforced panels. Such a CACS clinker 
is being developed by a single private venture, 
and its use is limited to local technical approval 
(Gartner and Sui, 2017).
z
The manufacture of cement based on
pre‑
hydrated calcium silicates (PHCS)
is beneficial 
because these materials can be easily produced 
at low temperatures and under pressure-
controlled conditions. Then, they are activated 
by intergrinding hard filler (silica-rich) materials 
and heating at low temperatures (UNEP, 2016). 
This type of cement can lead to CO
2
emissions 
savings compared to PC, through the use of 
high proportions of inert fillers such as quartz. 
However, the overall manufacturing process 
is complex, and there is still large potential 
for optimisation, especially on the activation 
through to grinding step. A first industrial-scale 
demonstration is planned for 2018 (ECRA and 
CSI, 2017).