Fly ash-based geopolymer concrete or alkali-activated fly ash-based concrete is a sustainable concrete that is not only reduced CO2 emissions, and also it utilizes waste materials such as fly ash, metakaolin, or blast furnace slag. This paper summarizes the recent improvements on mechanical properties of fly ash-based geopolymer concrete; its activating solution is a combination of sodium hydroxide, silica fume, and water. The results showed that the average compressive strength was reached up 103 MPa (15,000 psi) when the fly ash source was changed from Blewes Creek to Wateree Station. The need for external heat was overcome when up 15% of fly ash weight replaced by Portland cement. The initial and final setting time was extended due to using sucrose (granulated sugar), 3%-9% of fly ash weight. In addition, the cost of fly ash-based geopolymer concrete was reduced by 40% when three mix designs were introduced. The cost of fly ash-based geopolymer concrete is similar to Portland cement counterpart approximately.