Sustainable developments of technologies in industrial waste utilization
to concrete construction areas have been given considerable worldwide attention.
Among these waste products, fly ash from power plants has become a subject of
growing interests. This research shows the progress of geopolymer synthesis
based on high calcium fly ash. Two types of geopolymer product and three ratios of
fly ash to alkali activators were experimented. Alkali activators for this fly ash based
geopolymer consisted of sodium silicate and sodium hydroxide. The fly ash
contents were 60, 65 and 70 percents by weight and the weight ratio of alkali
activators was 1.0. Geopolymer products from fly ash were synthesized and
investigated by universal testing machine and thermal conductivity tester for
mechanical and thermal conductivity properties, respectively. Scanning electron
microscope (SEM)/energy dispersive X-ray (EDX) was used to determine the effect
of fly ash ratio on the properties and microstructure. Generally, the compressive
strengths of geopolymer mortar specimens above 30 MPa were reached after
curing at room temperature for 28 days. The results indicated that increasing the fly
ash to alkali activators ratio significantly increased the compressive strength.
Results also showed that thermal conductivity of geopolymer products were less
than 0.30 W/m.K. The EDX results confirmed that major elements of microstructure
consisted of Si, Al and O. It is expected that the geopolymer products will
contribute to the success of waste management. It has high potentials for
development in the area of precast concrete construction, thus promoting these
products for extensive use.