The trend in offshore and marine concrete is to use higher strength concretes (HSC) than have been used in the past. These concretes provide both additional strength and improved durability due to their improved microstructure. This is achieved by using greater cement content, supplementary cementing materials, and a low water-cementitious material ratio. HSC is more brittle than normal strength concrete and requires additional confining reinforcement to insure ductile behavior of the structural members. Higher strength steels and special methods of confinement, such as the use of T-headed bars, can contribute to the ductility of the concrete.
The use of HSC creates some constructability problems such as high concrete temperatures due to a large amount of cement present and significant thermal gradients. Reinforcing bar congestion in HSC requires concrete with smaller coarse aggregate sizes and very high slumps to satisfactorily place the concrete. Lap splicing in HSC can produce problems of concrete splitting unless the splices are properly confined. The use of mechanical couplers for splicing has some advantages in HSC. Proper curing with HSC is essential.