I read a bit about Ductal, a special concrete conceived by Lafarge and Bouygues. It has a whopping 180 MPa elastic limit in compression, a very impressive 40 MPa in shear, and still reaches 8 MPa in traction. That would be the ideal material for a long spar seastead based on the "suspended bridge" approach.
Alkali resistant glass fiber tested second after plain carbon steel in Navy tests in of uncoated composite cements in a marine environment. Both would be much better than rebar. Ductal looks very promising.
When we finally manage to get a chief scientist/engineer hired, one of the first tasks will be perform a spar material selection process. Concrete/steel, concrete/fiberglass, and pure steel will all be evaluated for price, performance, endurance, etc.
Any links to the concrete/fiberglass combination would be greatly appreciated.
Naval experiments , http://www.stormingmedia.us/38/3859/A385963.html , showed plain carbon steel fiber to have the best durability in a marine environment, followed by alkali resistant glass fiber.
Steel rebar which is prone to corrosion and spalling as the corrosion propagates down the length of the rebar. Good examples of this can be seen along the cement railing of the see wall on the San Francisco beach along Great Highway.
Ductal ?
I read a bit about Ductal, a special concrete conceived by Lafarge and Bouygues. It has a whopping 180 MPa elastic limit in compression, a very impressive 40 MPa in shear, and still reaches 8 MPa in traction. That would be the ideal material for a long spar seastead based on the "suspended bridge" approach.
Alkali resistant glass fiber
Alkali resistant glass fiber tested second after plain carbon steel in Navy tests in of uncoated composite cements in a marine environment. Both would be much better than rebar. Ductal looks very promising.
citations?
Any links to specific studies would be appreciated. There's a lot of noise in Google searches.
Are alkali-resistant glass
Are alkali-resistant glass fibers actually cheaper than steel? I would imagine it's a niche market. --Joel
Iron is NOT 'obsolite', nor
Iron is NOT 'obsolite', nor is it obsolete.. :)
with cathodic protection, any metal will last for eons in a marine environment
its still cheaper and easier to work with steel
Material selection
When we finally manage to get a chief scientist/engineer hired, one of the first tasks will be perform a spar material selection process. Concrete/steel, concrete/fiberglass, and pure steel will all be evaluated for price, performance, endurance, etc.
Any links to the concrete/fiberglass combination would be greatly appreciated.
Link Citations for Glass and Steel Concrete Composites
Naval experiments , http://www.stormingmedia.us/38/3859/A385963.html , showed plain carbon steel fiber to have the best durability in a marine environment, followed by alkali resistant glass fiber.
Ductal, http://www.ductal.com/ , University of Michigan's composite, http://www.umich.edu/news/index.html?Releases/2005/May05/r050405 .
Steel rebar which is prone to corrosion and spalling as the corrosion propagates down the length of the rebar. Good examples of this can be seen along the cement railing of the see wall on the San Francisco beach along Great Highway.
Summary of Alkali-Silica reaction in glass concrete, http://www.civil.columbia.edu/meyer/ .
Engineering data, http://www.retailsource.com/information/fiber_rc/fiber_rc.html