ABSTRACT
As described in Chapter 1, the saga of concrete in the marine environment is not over; in fact; it may be entering into a new era of intense activity. Oceans represent an inexhaustible source of water, food, energy and minerals which are vital to the sustenance and development of human society. Therefore, with the increasing shortages of materials on land, man’s search for additional resources is now focused on coastal and offshore areas. This is what Gerwick1 has to say on the subject:
Beginning with a water depth of 70 m (Ekofisk 1, 1973), most of the concrete offshore drilling platforms already in place are at water depths ranging from 100 to 140 m. The largest concrete
platform (244000 m3 concrete), Gullfaks C, is installed at 216 m water depth. The discovery of oil and gas in deeper waters (250 to 400 m) of the North Sea has brought forth new concepts for the design of concrete platforms. According to Hoff,2 as these structures become larger to accommodate the greater water depths and generally poor subsoil conditions that are associated with the deeper waters of the North Sea, their ability to float from the construction site to the point of installation on the sea floor many hundreds of kilometers offshore may be impaired unless lightweight aggregate concrete is used in making the structural components, at least in the upper regions of the structure. By reducing the concrete density while still maintaining high strength, tradeoffs between buoyancy and displacement can be achieved that will allow the structure to float and be towed with an adequate margin of safety.
