Technology Roadmap Low-Carbon Transition in the Cement Industry

Box 2: Data sources and the importance of getting the numbers right

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11
1. Introduction
and minimum maintenance, while a purposeful 
design can ensure the built application is future 
proof and remains relevant.
z
Reducing operational energy.
Optimal use of 
the inherent thermal mass properties of concrete 
can reduce the operational carbon emissions of a 
building over its lifetime. 
z
Contributing to the albedo effect.
For example, 
the light colour and reflective properties 
of concrete surfaces can result in lower air 
temperatures in cities and can reduce the need 
for lighting in tunnels.
z
Encouraging reuse and recycling.
Reducing 
the impact of new builds by reusing concrete 
buildings and infrastructure components and 
recycling concrete can reduce the demand for 
primary concrete, thus avoiding the carbon 
emissions associated with production.
z
Optimising recarbonation
. Cement based 
products absorb and chemically fix CO
2
over their 
life. Recarbonation is a slow process that can be 
enhanced, especially at end of life by increasing 
the exposed surface area with the ambient.

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12
Technology Roadmap
Low-Carbon Transition in the Cement Industry
Cement manufacture is a three-stage process: raw 
materials preparation, clinker production and clinker 
grinding with other components to produce cement 
(Figure 1). Different raw materials are mixed and 
milled into a homogeneous powder, from which 
clinker is produced in high-temperature kilns where 
direct emissions of CO
2
occur. Typically, 30-40% of 
direct CO
2
emissions comes from the combustion 
of fuels; the remaining 60-70% comes from the 
chemical reactions involved in converting limestone 
to calcium oxide, a precursor to the formation of 
calcium silicates, which gives cement its strength. 
Clinker is then interground with gypsum to produce 
cement. Other components, including fly ash, 
ground granulated blast furnace slag (GGBFS) and 
fine limestone, can be interground or blended, 
depending on the required technical properties 
of the finished cement. Cement can be produced 
at the kiln site, or at separate grinding or blending 
plants. Blended cements or “combinations” can also 
be produced at the concrete plant.
There are two basic types of clinker production 
– “wet” or “dry” – depending on the moisture 
content of raw materials, and there are also different 
kiln designs. The wet process consumes more 
energy than the dry process, as the moisture needs 
to evaporate.
The cement making process is complex – it requires 
control of the chemical formulation and involves 
multiple steps that require specialised equipment.