Properties and durability of concrete containing fluidized bed combustion (FBC) fly ash

As the supply of conventional pozzolans fall further behind concrete industry's demand, interest in non-traditional pozzolanic materials continues to grow. One such material is fluidized bed combustion (FBC) fly ash. In this study, two compositionally different FBC fly ashes from North America were used at 20% mass replacement of Portland cement in a pavement-grade concrete mixture. The effects of these fly ashes on the fresh, hardened, and durability properties of concrete and equivalent mortars were evaluated. It was observed that desirable slump, air content, air-voids structure, and strength development can be achieved in concrete with FBC fly ash. Further, FBC fly ashes improved concrete's resistivity, formation factor, and resistance to chloride penetration. Drying shrinkage performance was also acceptable. While the high SO₃ content of one fly ash did not cause a deleterious expansion by itself, the concrete containing the high SO₃ fly ash was more prone to sulfate attack.