Geopolymers are highly alkaline binders used as an alternative for the replacement of OPC in the manufacture of concrete. The advantages of using geopolymers are that they impart excellent mechanical strength, help in reducing carbon di-oxide emission and helps in achieving good durability properties. In addition, the increasing demand for river sand, are leading to environmental effects, thus developing an urgent need to replace river sand with an alternative construction material. Geopolymerization of fly ash in 10 M NaOH and Na2SiO3: NaOH= 1.8:1 solution at 100°C for one hour produced geopolymer fly ash aggregate (GFAS) to produce an alternative replacement for river sand. The specific gravity of GFAS was 1.82 indicating that these particles were light weight. The properties of concrete such as compressive strength and flexural strength was also studied by replacing river sand with GFAS in concrete. It was observed that the mechanical strength of the GFAS was nearly same as that of the river sand concrete, thus indicating GFAS can be used as an alternative material to replace river sand in concrete.
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