Compressive strength and rapid chloride permeability of concretes with ground fly ash and slag

Concretes with binary and ternary blends of portland cement, finely ground fly ash and finely ground granulated blast furnace slag were produced to investigate their effects on compressive strength and rapid chloride permeability. Portland cement was partially replaced by finely ground fly ash (Blaine specific surface: 604 m²/kg) and finely ground granulated blast furnace slag (Blaine specific surface: 600 m²/kg). Two series of concrete with water/binder ratios of 0.60 and 0.38 were produced and for both water/binder ratios, portland cement was replaced by: (i) 50% fly ash; (ii) 50% blast furnace slag; and (iii) 25% fly ash+25% blast furnace slag. At the high water/binder ratio, compressive strengths of the concretes with the pozzolans are lower compared to that of the portland cement concrete. At the low water/binder ratio, however, these strength reductions are less compared to the high water/binder ratio and compressive strength of the concrete produced with 50% slag was even higher than the portland cement concrete. The test results indicate the ground fly ash and ground granulated blast furnace slag greatly reduce the rapid chloride permeability of concrete. It was concluded that to reduce the chloride permeability of concrete, inclusion of pozzolans are more effective than decreasing the water/cement ratio.