The main objective of this paper is to highlight fly ash current utilization in construction industry, and explain advantages attained by incorporating different types and contents of fly ash in the concrete mix. Fly ash is currently used as a supplementary cementitious material (SCM) in ordinary Portland cement (OPC) concrete in partial replacement of cement and is recently used as a geopolymer cement in the development of geopolymer concrete (GPC) mixes. Class C and Class F fly ash high aluminosilicate content, and fine granular size contributes to concrete improved workability, lower permeability, and reduced heat of cement hydration. Due to its chemical properties, the use of fly ash in producing OPC and GPC results in increased compressive strength, higher tensile strength, and higher modulus of elasticity (MOE). The fine size of fly ash particles increases the concrete mix packing order, reduces the ingress of moisture, and mitigates the impact of aggressive environmental attacks through the reduction of sulfates and chlorides rate of concrete penetration. Thus, fly ash improves concrete resistivity to alkali-aggregate reactions (AAR), and reduces the corrosion of reinforcing steel, and prestressing strands. Fly ash as an economic byproduct of coal industry results in reduced material cost, increased durability, and a higher sustainability of concrete construction projects.