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Message: <blockquote data-quote="RP1" data-source="post: 54545" data-attributes="member: 64">I just did a project for the EU on concrete ocean structures... it's actually quite a good material for offshore structures and submarines, being strong in compression. For ships less so, as they are subject to tensile loads. However, with appropriate pre-stressing this can be overcome. Concrete has successfully been used for barges and a few ocean going vessels. It's particular advantages are; long life (DNV has classed some LNG storage barges as having an unlimited life span) and low maintenance, ease and speed of construction (training for concrete is easier than for quality welding) and resistance to damage and extreme cold (some concretes gain strength when subjected to low temperatures). The problems are avoiding tension, increased weight, severe problems if the quality is not maintained (porosity etc) or construction is interrupted and some difficulties in repair (if still at sea - in dry dock it should be simple). It can also be difficult to attach fittings - you can't weld to concrete, so normally a steel plate is cast into the concrete around the location of the fitting.Concrete by default is porous and water will infiltrate it, but only at a slow rate and to a depth controlled by the pressure inside the material (remember it is under compressive loads). Chloride ion infiltration can be a problem in that it will corrode re-bar and tensioning tendons but this can be avoided by either increasing thickness or using special types of concrete, including high density and waterproof types, special coatings or mixtures containing additives such as polymers - the latter have been used on some large offshore projects.RP1</blockquote>

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