Is there an admixture for use with Type I cement to make Type II or Type V cement unnecessary in concrete for piers in ocean water? We cannot get those types of cement in our area right now.
We do not know of an admixture that can be incorporated into a Type I cement concrete to produce the equivalent of a Type II or Type V cement concrete. It is widely recognized, however, that concrete for seawater exposure should first and foremost be of high quality; any admixture which contributes toward making concrete less permeable would be beneficial in concrete exposed to seawater. Type V cement is not needed for concrete exposed to seawater. Type II is recommended but it is not always available everywhere and in times of cement shortages it is likely to be very short in supply. A number of agencies are using Type I for concrete exposed to seawater. One such agency is the Florida Department of Highways, which has used Type I for prestressed concrete piles in bridge structures exposed to seawater for a number of years and has experienced no difficulty. A 43.3-million-gallon oil tank recently built of prestressed concrete for the Ekofisk oil field and submerged on the floor of the North Sea was made with Type I cement. The mixture was designed for high strength and low permeability. Of primary importance is the water-cement ratio and the amount of cover over the reinforcing steel. The water-cement ratio should not exceed 0.45 if Type I cement is used and the concrete cover should be a minimum of 2 inches and preferably 3 inches. Finally, sufficient moist curing is essential to develop fully the desirable properties of the concrete.