Eight concrete mixtures were prepared using the same batch of ordinary portland cement (OPC) and ground low-lime fly ash. The aggregate grading used in the mixtures of concrete, water-binder ratio, and the maximum particle size of aggregate were kept constant in all concretes, but the partial replacement of cement by fly ash was varied from 0%(OPC concrete) to 70% in steps of 10%. The replacement was on a one-to-one weight basis. At 28 days, there was little reduction in compressive strength up to 40% cement replacement by ground fly ash; then a significant decrease was recorded for the further fly ash dosages. At 56 and 120 days, however, the compressive strength up to 40% cement replacement by fly ash is almost identical to that of the no fly ash concrete and for one year it was even higher. The results of the rapid chloride penetration tests indicated that high volume ground fly ash concrete had better resistance to the penetration of chloride ions.