cules. Similarly in geopolymers, it is the highly polymerized regions
that are resistant to
chemical attack and
offer long-term stability, whereas the less
polymerized
regions
with Al-OH or Si-O-AlO-Si- species are prone
to shrinkage and leachability.
T.D. In the context of durability of geopolymer materials, how well characterized are the gel pores, cement hydration and alkali-aggregate reaction? What improvements can we, the scientists, make in order to further
optimize the product?
Dr. Davidovits
Pore solution analysis
is worthwhile for monomeric/dimeric gels like
those found in Portland
cement or alkali-activated slag for example.
It is not valid for the
investigation of any fully
condensed geopolymer
matrix. It may be used
to show that geopolymerization, i.e. networking of the framework, is not complete.
Instead of pore solution
analysis, we measure
the pH of the material and perform Nuclear
Magnetic
Resonance
spectrometry (NMR) for
silicon (Si) and aluminium (Al).
As for alkali-aggregate
reaction, I published
my first study on this
topic 20 years ago, in
Ceramic Transactions,
Vol. 37, (1993), CementBased
Materials:
Present, Future, and
Environmental Aspects.
pp 165-182, titled:
54
Geopolymer Cements
to Minimize Carbondioxide GreenhouseWarming. The demonstration was clear.
Geopolymer
material does not generate
any deleterious alkaliaggregate reaction.