Cost of building a floating construction facility


(noboxes) #21

Only if you insist on stretching it that much.


#22

That is the problem with concrete it doesn’t elongate at all. . . It is brittle like ceramics. A ceramic hull would be very cool : )


(noboxes) #23

I have seen concrete bridges sag when heavy loads drive over them. Very tall concrete buildings are known to sway in the wind.


(Larry G) #24

The concept you’re looking for is “co-efficient of thermal expansion” and it is very similar for cement and basalt. MUCH closer than for cement and steel rebar. Basalt fiber has a higher tensile strength than steel, similar flexural modulus to glass fibers, and it’s better suited to embedding in geopolymer than fiberglass is in OPC. Silica in OPC tends to form gels that weaken the overall compressive and tensile strength of the finished concrete. Silica and aluminum in geopolymer become part of the polymer (long-chain molecule) and thus add to its strength. Geopolymer cement has greater flexural modulus than OPC regardless of the armature’s composition.

Perceived value can change drastically in short periods of time. All value is relative. What may be valuable for a seastead may never be worth pursuing for shipping, and vice versa.


#25

What is the elongation of “Cement” and Basalt Rebar?

By comparison Fiberglass is 4.8% and epoxy is 6%.

Basalt fiber is 3.1% and its coefficient of expansion is 8. Basalt is pretty good stuff, expensive but good.
I tried and failed to find the elongation of cement, concrete, aggregate, etc. and couldn’t find any data. I think it would be close to zero.

Do you understand the problem?


(noboxes) #27

Yes: If you design such that the OPC is in tension, you have instantly shortened the lifespan of your project. How are you feeling?


#28

Autocorrected from “more”…

@Talador

Would have been far more appropriate to ask what I meant, rather than create strife.


(Larry G) #29

It’s a discussion forum. One of our community standards is to "Be Nice.

People have different levels of personal knowledge about different things. Please try to keep the conversation constructive.


#30

https://www.google.com/url?sa=t&source=web&rct=j&url=http://civil.colorado.edu/~hearn/concrete/Loads/Material%20Properties.pdf&ved=0ahUKEwjdqcDeroXYAhUBTyYKHQiiBo4QFghKMAU&usg=AOvVaw3jaNclEt8D7ciMtm309wu8

http://www.ijmer.com/papers/Vol2_Issue6/AG2640224025.pdf


#31

I am not sure what you mean by OPC? Prestressed Concrete? It increases the lifespan of the project.


(noboxes) #32

Ordinary Portland Cement


#33

Ordinary Portland Cement is the slaked lime in mortar and concrete


#34

Wiki is correct, Concrete fails in tension. If your application requires tensile strength concrete (cement) is not a good material to use. Although it can have tremendous tensile strength prior to failure.

Why not use basalt fibers with epoxy?


(Larry G) #35

That’s been done, and it’s viable. The issue is the UV resistance of epoxy is not great for something that you want to last for generations. Despite the fact that many fiberglass boats get decades of use with proper maintenance, the haul-out for that maintenance is the issue if you start talking about very large structures.


(noboxes) #36

Which is why i mentioned smaller floatation that could be replaced while afloat (which was poo-poo’d).


#37

Use the search function. It is your friend.

FWIW, I even found a way to make thermoplastic Basalt Rebar, using enamel, rather than the industry norm using thermoset resins and such. Once embedded in cementitious material, whether OPC, or Geopolymer, it would retain the desired shape until the entirety was heated up enough to change the previous ‘set’.

Think of a fiberglass bow. It has a ‘set’ to give it the desirable spring rate, when under tension of the bow string.

Composite rebar is made as long, straight pieces, then rolled into coils, and under tension. Building a curved form, such as a hull, would incrementally adding built-in tension. My purpose was to remove that and replace it with a desirable characteristic that reinforced the hull configuration.


#38

Ahh, it worked, who would have guessed? So the elongation of concrete is .1% to .3% or an order of magnitude less than Basalt fibers.

That is a perfect reason not to use Basalt fibers with Concrete (cement) the fibers aren’t doing anything at all. I just saved everyone a ton of money.

Just build the boat out of Ordinary Portland Cement, what could be cheaper and easier?


#39

You go for it. I’ll trust a Basalt Armature, for mine, thank you very much. They share the same characteristics…

By the way…

If numbers differ by one order of magnitude, x is about ten times different in quantity than y. If values differ by two orders of magnitude, they differ by a factor of about 100. Two numbers of the same order of magnitude have roughly the same scale: the larger value is less than ten times the smaller value.


#40

Remember, the process is creating a composite… Composites share properties of their component parts.

Concrete is, itself, a composite. Different mixes, different admixtures make for different properties.


(Larry G) #41

You seem to be confusing or conflating some things. If you are talking about modulus of elasticity or ultimate tensile failure, then you have it backwards. “Elongation” does not seem to be the correct term. I think you mean the maximum elongation before final tensile failure. If so, it is still irrelevant to the discussion, or at best, tangential.

Tensile strength, and maximum elongation before tensile failure are not the same thing.

If the tensile strength of the basalt fiber prevents elongation of the cementitious matrix, then the cement never gets to tensile failure. There’s usually an elastic modulus ‘zone’ where your elongation or bending (elastic deformation) happens and the material will return to normal shape when stress is removed. Then there’s an amount of force that will exceed the material’s elastic modulus and result in permanent plastic deformation such as ductile elongation or brittle failure (fracture).

Portland Cement has a poor elastic modulus. Steel and basalt fiber (and for that matter, geopolymer) have better elastic modulus. So an armature is required within the cement that has better tensile strength than cement to prevent tension from exceeding the tensile strength of the cement. It does this by distributing and absorbing the load in the armature rather than leaving the load to exceed the cement’s ability to adhere to itself. Particularly if the armature is pre- or post-stressed, it allows less movement than would be required to cause tensile failure in the cement.

Basalt more nearly matches the natural thermal expansion rates of cement than steel does, so there is less opportunity for the armature itself to cause stresses that exceed the elastic modulus of the cementitious matrix. Basalt does not corrode, so there is less chance of spalling due to expansion of the armature itself within the cementitious matrix exceeding the elastic modulus of the cement. Basalt and geopolymer chemically bond, incorporating the silica into a polymer-like long chain molecule, increasing the elastic modulus of the geopolymer cement rather than weakening the bond between cement and armature (or glass aggregate in concrete) like fiberglass in Portland Cement does.