Abstract :
Geocements were created in accordance
with a hypothesis put forward by Prof. V. Glukhovsky
that the structure formation processes in the alkaline
aluminosilicate binders corresponded to geological
transformations of aluminosilicate minerals taking
place in nature. At low temperatures, a type of
hydration products depends on curing conditions and
mix composition. An autoclave curing allows for an
intensive synthesis of a well-crystallized zeolite structure,
whereas other types of curing result in the
formation of an amorphous structure with crystalline
inclusions represented mainly by hydroxysodalite. On
the contrary to this, after curing at high temperatures, a
formation of nepheline, albite or a-cristobalite depends
exclusively on the firing temperature and initial geocement
composition.
Mechanical strength of the geocements may reach
88.5 MPa after low temperature curing and 88.7 MPa
after firing at 800 C. Optimal thermo-mechanical
properties of the metakaolin- and fly ash-based geocements
may be reached in compositions with a microstructure
represented by an average amount of
thermostable zeolites, since just these phases are
characterized by a smooth dehydration and subsequent
re-crystallization into stable anhydrous alkaline aluminosilicates
without destruction of a framework. Directed
regulation of structure formation at low
temperatures is a key question in obtaining a wide
range of special materials such as acid-resistant, highstrength,
quick hardening, with low leach rates, high
adhesion, etc. At the same time, a structure formation
at high temperatures is important with regard to
creation of heat- and fire-resistant composite materials.
Synthesis of analogies to natural aluminosilicate minerals
ensures also high durability.
