Most of the soluble salts and free lime needed for efflorescence are provided by cement. The main chemical constituents in POFA are SiO2, Al2O3, Fe2O3, CaO, and MgO. The SiO2 from POFA reacts with free lime released by the hydration of Portland cement and generates Calcium
Silicate Hydrate (CSH) as a gel. The CSH gel is the main binder that holds together the aggregates reduces permeability. Thus the lower the cement content and higher the POFA, the lower is the possibility of efflorescence.