| Summary: | Coal fly ash is an overwhelmingly produced waste, but the utilization is
still very limited in certain construction fields. The chemical composition of fly
ash is generally dominated by various kinds of oxides such as CaO, Al2O3, SiO2,
Fe2O3, MgO, and other oxides, which are good raw materials for making the
glass-ceramics composites. The aim of this study is to find out the utilization of
coal fly ash and glass waste in making the composites materials of fly ash and
glass waste (FA-GL) by a pressureless sintering process.
The study was started by characterizing several raw materials including
as-received fly ash, calcined fly ash, and glass waste powder. To avoid any
change in composition resulted from the effect of LOI (lost on ignition) during a
sintering process, calcination was done on as-received fly ash at a temperature of
800 °C. Distribution of particle size was obtained by sieving the calcined fly ash.
The making of glass-ceramics specimen was done in various fly ash�glass
composites (% of weight), i.e. FG55, FG73, FG82, FG91, and FG100 in various
compaction pressures of 70, 100 and 130 MPa. Formed green body was sintered
at various temperatures of 900, 950, 1000, 1050 and 1100 °C. The observation of
microstructure was done using SEM, chemical composition using EDX, and
crystal phases in the materials using XRD. Furthermore, density, porosity, water
absorption, hardness, and bending strength tests were done. Specimens with
treatments giving the best properties were selected as references in making the
specimens for thermal shock treatment. The giving of thermal shock effect was
done by reheating specimens at various temperatures, then quenched into water at
a room temperature, while after dried, a bending strength test was done.
Result of the study shows that the weight of fly ash will decrease 1.433 %
resulted from calcination for 2 hours at a temperature of 800 °C. Manufacturing
parameters such as mixture composition, compacting pressure and sintering
temperature greatly affects the properties of FA-GL composite materials
produced. The highest value of density is 2.103 ± 0.038 g/cm3 with porosity of
17.726 ± 1.164 % and water absorption of 8.834 ± 0.624 was obtained from
specimens of FG55 with compacting pressure of 130 MPa and sintering
temperature of 1100 °C. The highest hardness value of 2205.205 ± 539.684 MPa
is obtained from speciment of FG55 at a temperature of 1100 °C with compacting
pressure of 130 MPa. The highest value of bending strength of 44.533 ± 4.162
MPa is obtained from speciment of FG55 at a temperature of 1050 °C with
compacting pressure of 130 MPa. The bending strength will sharply decrease
around 80.92 % from its original strength if the materials has a temperature
difference of �T is 285 °C. The highest fracture toughness of 1.665 ± 0.038
MPa.m0.5 is obtained from speciment of FG55 with compaction pressure of 130
MPa and a sintering temperature of 1100 °C. Manufacturing parameters with
optimum properties is obtained from mixture composition of FG55 with
compacting pressure of 130 MPa and sintering temperature of 1050 °C.
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