2.1.2. Aggregate
Coarse aggregate was used as a primary ingredient in making
the permeable concrete. According to Krezel [10], crushed igneous
rocks are more preferable as coarse aggregate for concrete due to
their higher strength. However, since the availability of igneous
rock in Australia is becoming scarce [10], this research diverted
to the crushed sedimentary and metamorphic rocks. Three types
of coarse aggregate were obtained from local quarry: quartzite,
dolomite and limestone. Dolomite was a sedimentary carbonate
rock, composed of the mineral dolomite, also contained impurities
such as calcite, quartz and feldspar. Dolomite formed in groups of
rhombohedral crystals with curved, saddle-like faces. Limestone
was also sedimentary rock. Although some limestones were nearly
pure calcite, there were often varying amounts of clay, silt and
sand. Quartzite was a dense, hard metamorphic rock. The quartzites
obtained from local quarry were red due to a large amount
of iron oxide. In order to explore the optimum aggregate for making
porous concrete, these three types of coarse aggregate were
investigated and compared at the first stage. The geological and
mechanical properties of aggregate were tested and the results
were given in Table 1.
In addition, considering the smaller size aggregate will result in
the increase of the specific surface and the binding area between
cement and aggregate, which is beneficial to the strength
and durability of concrete, fine aggregate was used at the second
stage.