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TECHNICAL PAPER COLLECTOR’S EDITION

is the main parameter determining strength
development (Figure 9).

In these experiments the cements were prepared
by intermixing based on the same ground clinker.
It can be seen that the one day strengths are still
rather low, but, for a kaolinite content of 50% or
more, higher strengths than the reference are
achieved by 7 days. In practice one day strength
can be improved by intergrinding as is currently
done for many fly ash blended cements.

3
Durability of LC cements
When considering a new cement formulation,
the question of durability is of prime importance.
reduction scenarios is evaluated in relation to the Will these materials perform as well as existing
results of the WBCSD CSI study [7] (Figure 7). This materials over the lifetime of a typical building or
assumes that the supply of SCMs can be increased structure? A wide-ranging and detailed study of the
by a fairly modest 600 million tonnes worldwide by durability of LC is underway in Switzerland, India
3
3
2050. This graph shows how LC can significantly and Cuba. This study will look at the underlying
contribute to the growth of the cement sector scientific mechanisms as well as full scale exposure.
without increasing emissions. This is more feasible However, we have every reason to expect that
than compensating a business as usual strategy these materials will have good durability:
with carbon storage and capture. Importantly, the
3
uptake of LC would allow developing countries
to satisfy rapidly growing demand while reducing 1. First, the phase compositions of the
the CO intensity of their activities and is thus materials is very similar to existing Portland
2
a politically very attractive global environment and blended cements. The principal
option. hydrate is calcium silicate hydrate, C-S-H,
whose long-term behavior is well known
and understood. The other aluminate
3
Strength of LC blends prepared from containing phases, mono and hemi
low grade clays
carbonate and ettringite are also formed in
Further investigating the potential of blends based limestone cements, widely used in Europe
3
on limestone, calcined clay, and clinker (LC ), blends for many years.
incorporating calcined clay from several countries
2. Second, analysis of the pore structure
(India, Brazil, Thailand, Cuba) were analyzed. An
shows that, as for other blended cements
example of the strengths obtained is shown in
[e.g. 12], the pores are smaller, even though
Figure 8.
the overall porosity may be slightly higher
(Figure 10) [13].
Plotting these results against the kaolinite content
of the clays, it can be seen that kaolinite content 3. Third, preliminary results on the resistance
to penetration of chloride ions are extremely

140 The Indian Concrete Journal | November 2018