| dc.description.abstract | One of the great contemporary challenges to mitigate CO2 emissions in the earth's
atmosphere is the production of cements with reduced emissions of this gas that
causes the greenhouse effect. Therefore, seeking to reduce the use of clinker in
cement, new alternatives are tested, among these, the study of ternary compositions,
such as LC3. The use of calcitic limestone is discussed a lot, but very little is said
about the use of dolomitic limestone filler, due to the hypothesis that the magnesium
present causes a negative impact. Thus, we sought to investigate the hydration of
ternary compositions composed with carbonate fillers of different mineralogies and
calcined clay from the Amazon region. The composition used is in accordance with
the literature, being 50% clinker, 5% gypsum, 30% calcined clay and 15% limestone.
Pastes with three types of carbonates were prepared for proper comparisons. In view
of the climate in the states of the Legal Amazon, and its effect on the temperature of
cement hydration, the produced pastes were cured at temperatures of 21 °C and 60
°C, and tested for 7, 28 and 91 days of age. The results showed that excess
magnesium tends to react in the composition with the alumina of the cement, forming
products such as brucite, at both temperatures, but with more evident formations at
the temperature of 60 °C, according to DRX. When magnesium and alumina are
mixed in excess, portlandite tends to be completely consumed, which may lead to
problems in compressive strength. The paste containing magnesium carbonate and
cement proved to be the ideal scenario regarding the amount of magnesium and
alumina for hydrotalcite formation at both curing temperatures, being more intense at
60 °C. The dolomitic limestone used in LC3 showed results similar to the reference
limestone, usually used as calcitic limestone, with compressive strength results
above 30 MPa, without formation of brucite, hydrotalcite or thaumasite, with curves of
calorimetry, thermogravimetry and product phases hydrates similar to each other. In
view of the study carried out, it is possible to state that dolomitic limestone has the
potential to be used as a dolomitic filler in LC3, under the boundary conditions of this
study. | en |
