4. Conclusions
This study presents preliminary investigations about the
effect of aggregates on the microstructure and mechanical
behaviour of geopolymeric mine waste mud binders. Based on
the experimental results the following conclusions can be drawn.
GMWM based binders showed very high strength even at
early ages confirming the extreme reactivity of mine waste mud
when activated with a highly alkaline solution. The addition of
aggregates increases strength behaviour acting almost as a
catalyst. It's suggested that may be due to the dissolution of
quartz and alumina in the presence of alkalis enhancing bonding
between paste and aggregates. Other hypotheses related to
aggregate type could not be confirmed.
Unlike OPC systems GMWMbased binders possess extremely
high tensile strength. Tensile strength begins to decrease after
14 days of curing although it is not clear why that happens. It is
suggested that may be due to shrinkage cracks near the
aggregates. In alkali-activated based binders schist and granitic
aggregates are chemically reactive increasing strengthwith curing
time. A dense and uniform ITZ was detected in GMWM based
binders. Mixtures with limestone aggregates showed that
GMWM paste chemically bond to the aggregates but present
higher shrinkage which may explain random strength behaviour.
In order to confirm the results obtained in the present study
further research is still required using aggregates with different
sizes and different water absorption.