Concrete IS Your Friend

* See also Construction
* See also UnderWater_Construction
* See also Rebar
* See also City_Foundation
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Rapture's Hydraulic Cement ( modern concrete cement ) :
The Romans built partially-underwater harbor structures out of Cement, which are still there 2000 years later ( was a different mix than modern cement ).
1824 - Portland Cement invented in 1824 by Joseph Aspdin
1908 - Thomas Edison was experimenting with building pre-cast Concrete Houses in Union, N.J Edison in his 'cement phase' even attempted to manufacture cast concrete furniture. https://www.scientificamerican.com/article/thomas-edison-invents-cheap-concrete-furniture/
1909 - Construction of the world’s first mile of concrete highway
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Concrete Use :
The Buildings were made up near the surface where their detail work was far simplified versus building them below.
The Cement used was economically manufactured on the mainland and shipped via freighter to Rapture. Pneumatic pipes were utilized to efficiently deliver the quantities of the powdered material below.
Concrete mixed below was largely used to build the building foundations and to anchor the surface prefabricated buildings into the sea bed.
Huge amounts of concrete was consumed. The facilities below, used to properly mix it, were located close to where the concrete was used.
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"Gunnite(tm)" (aka Shotcrete) :
Sprayed on Cement (invented in 1907) - Fast Concrete Application
Useful for reinforcement of Tunnels ( with embedded reinforcing wire mesh ... )
1907 used to reinforce the crumbling facade of the Field Columbian Museum in Chicago ( the old Palace of Fine Arts from the World's Columbian Exposition 1893 )
Used in Rapture for Tunnel work ( repeatedly applied layers of reinforcement )
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 "Transite" - Asbestos in Cement
Used to strengthen cement - much of it to prevent cracking as the cement/concrete set.
So, expect some Asbestosis in Rapture - now healable with the ADAM medical therapies.
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Disney's Magic Kingdom Based on Real World Realities : 
5000 cubic yards of concrete used for initial building of Disneyland (1955)
~27 * 5000 = 135000 cu ft (rough volume)
2 X 50 x 50 M = use for 6 ft thick wall x 6 sides/facing of a cube x 61 feet wide (equiv to a 3 floor Small Building )
AND add lots of Rebar ...
POINT - Rapture would REQUIRE A WHOLE LOT OF CONCRETE to build it
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Concrete, The Solution :
Slab concrete was a characteristic of the new Art Deco Architecture ( used as a fairly new building material at that early time - 1920s ). In Rapture, Concrete would be legion (being cheap, strong, and able to be prefabricated), needed (heavily reinforced) for the buildings' strength to hold out the massive water pressure. The basic concrete structures would be formed into 3-dimensional cells, to support in all directions against the environmental forces. Thus Concrete would be employed to an even greater extent than on The Surface ( the other aspect of Art Deco was the decoration which was then fastened to the concrete ).
Decorative Molding could be done integral to the prefab concrete castings, with a whole variety of nice Art Deco texture patterns. Likewise, it is simply shaped to be the 'Canvas' for additional decoration added later ( once the interiors are accessible ).
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Ferro-Concrete - Steel Reinforced Concrete :
The Rebar ( reinforcement bar, placed within the concrete to add tensile strength ) used was usually Steel, but that has long term Salt Water corrosion problems ( problematic in Rapture ).
Aluminium resists salt water corrosion better, but still for the Long Term is insufficient. Other specialized reinforcement materials (wires/fibers) are possible, but with an added expense.
Basalt Fiber rebar ??? A fibery melted rock material with useful tensile properties, and is fully resistant to salt corrosion ( thus allowing a long functional lifespan ). It might be a possible option using local sources of volcanic rocks, combined with the Plasma heating technologies used in Rapture. Its use would likely be selected when the city was being planned.
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4.5 Million cubic yards of concrete used on Hoover Dam project - How much was used to build Rapture ? :
http://outoflasvegas.com/wp-content/gallery/railroad-pass/damupstream.jpg
http://www.beowulf99.com/Galleries/Vegas/images/HooverDam.jpg
http://www.funinstore.com/wp-content/uploads/2012/01/8.hoover_dam.jpg
http://denverpost.slideshowpro.com/albums/001/496/album-271297/cache/hooverdam12.sJPG_950_2000_0_75_0_50_50.sJPG?1318358295
http://www.jimcollier.com/Chronological/2010/2010062001/i-6Lb5f6v/1/L/20100622202692-L.jpg
http://outoflasvegas.com/wp-content/uploads/2010/11/750x650_Dam-crossection.jpg
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Construction - Concrete :
There has been (real world) talk of using some Roman Era formulations for Underwater use ( combination of lime and volcanic ash ) which have held up for millennia ( though that type of cement might NOT really be particularly strong concrete -- just durable - Still there would be specialized uses for that in Rapture ). Modern formulations would likely make adjustments and improvements.
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Face it, Rapture is a Heap of Concrete :
Yes, some spectacular parts of Rapture are gleaming metal, and having those impressive expanses of windows, but the vast mass of the place would HAVE to be reinforced concrete. If it were to be all that miraculous Ryanium stuff, how many million tons of that would be required ? 
Lets Assume that some of it IS 'metal', and almost certainly those large windows would have to be made of some super strong material to withstand the likely depths at which Rapture exists (( Ignoring that ridiculous 5-6 miles deep crap )) -- It is problematic enough to have it (more realistically) merely around 600 feet -- Deep enough to allow buildings tall enough to plausibly resemble the spirit of the views we are shown in-game. 
Required Materials with sufficiently high tensile strength usually don't work too well when compression forces occur as well (thus weak under realistic shear forces). Concrete works best in compression, when used with with added reinforcement to give it some partial tensile/shear strength ( for Rapture - Ryanium Rebar ? ). This combination has the properties to handle all three problems. Rapture's architecture ( and its engineers) would take advantage of these properties. Thus being thick walls, allowing compression support to be employed most of the time -- generally with a Monolithic form for the same reason, having sufficient internal bracing (between floors) which channel the existing compression forces ACROSS the whole structure, and using a honeycomb pattern to generate the required solidity.
All of this structure is largely hidden from the interior spaces - except for for some visibly thick walls, and many extra corner reinforcements, so it doesn't change the original games' appearance much.
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Concrete --- Concrete is Rapture, and Rapture is Concrete :
Millions of tons of hydraulic (underwater setting) Cement - and many times as much aggregate and rock, were used to build Rapture. Why is the concrete so thick ? Because for every ton of concrete in the structure there is 100+ tons of water sitting ontop of it pressing in at every angle on every surface. Steel might be stronger, but similar construction would be far more expensive ( It is why things in the Real_World likewise are made from concrete and not just steel ). 
A surprising statistic is that for every person in Rapture, there would have been something like 1000+ tons of concrete. ( THINK about ALL the infrastructure that exists in the Real-World to make your modern life work and you might realize that the real amount is something similar ). So, cheap production and employment of concrete would have been a necessity.
Cement Plant operation :
* Mass of raw materials (and fuel) brought in, processed, and finished product (powdered cement) going out
* Huge amounts of electricity/power used in the Calcination furnaces ( heats up to 2600 F ) - some advanced Ryan 'power tech' may have improved the efficiency (electric furnaces, plasma technology) and power available from Hephaestus was plentiful ( and capacities unused before the people moved in ).
Aggregate :
* 4 to 5 times as much sand and aggregate (broken rock) are added to the cement to make 'Concrete'.
* Volcanic sand was available in nearby deposits ( from current erosion ), and Aggregate was made by crushing appropriate igneous rocks ( from the ancient volcano's ( Mt Ryan's) lava flows ).
* Concrete's strength is limited by the strength of the aggregate (filler rock). So the material used would be carefully chosen for strength, as well as dimensional stability, chemical neutrality, and to have little temperature/water expansion qualities.
Purified fresh water is used to mix the concrete to avoid contaminants (like salt) that can accelerate corrosion ( of common steel Rebar ), or would weaken the cement itself.
Mixing on-site - portable concrete mixer units with short working time, to which the concrete's raw materials are transported from the various sources - via Trains and Trams.
Pouring Forms to solidly hold the cement secure while it sets ( starts setting sufficiently ).
Cement 'cranes' to hydraulically pipe the fresh cement direct into the construction points.
Concrete Setting Delays - It usually takes months for the cement to fully set and to achieve its full strength, so buildings would wait before being pumped out and subjected to the stresses of full ocean water pressures. In the mean time, waterproof windows/doors/mechanisms/pipes would be added/installed to the building.
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Bulk/Mass Fillers :
'Plum Stones' ( large chunks of stable/strong rock - capable of withstanding the forces the building would be put under ) are embedded in large solid masses of concrete ( saving on the amount of concrete required for the buildings volume ). Foundations which anchor building to the seabed are usually bulky/masses of concrete.
Access Tunnels (voids) inside the Concrete structures are used to lessen the amount of concrete needed to fill the required volume. They are used for drainage and inspection and utility spaces.
Structural Reinforced Concrete - Ryanium and Steel ( and other materials ) - To increase the Concrete's tensile strength ( which Concrete by itself largely lacks ). As long as the cement seals properly, the Steel Rebar can remain largely unaffected by the Ocean's salt water ( various sealing compounds can increase the corrosion resistance ).
( Watch one of the documentaries of how they built Hoover Dam to last 1000 years - How specific/careful the Construction Process was to get the best quality concrete formed and to form/pour it correctly ).
Concrete contracts in dimension as it sets, and is usually cast in layers and in separate blocks, which are later 'grouted' in between to fill the gaps. The Concrete also gets stronger as it sets (over years), so Rapture's Foundations and Concrete buildings/structures are actually stronger in BS2 than earlier. They were constructed to be several times stronger than needed anyway, as per normal engineering practices.
You may notice on my various extended level maps ( redrawn/corrected from the Solo games ), the buildings outlined by 'Black' which represents the primary structural walls of Reinforced Concrete. Where those walls penetrate the Seabed, an outer layer shown as dark grey represents mass concrete (mostly non-reinforced), to wedge/anchor the structure into the Sea-floor. The standard practice was to dig out the seabed for the foundation, often a fairly irregular hole, with sufficient working room ( mostly dozens of feet down into the seabed rock ). The structural walls were then carefully build up on pilings ( or positioned when sections were prefabricated closer to the surface ), with reinforcements tied/woven together within the pouring forms. Once that structure was properly filled, shaped and had set, the seabed would be backfilled with mass concrete to further anchor the building. Tall buildings require especially deep foundations and concrete pilings would be laid much deeper into the seabed rocks to strengthen the foundation further.
Transportation - the Atlantic Express Built Rapture :
All the construction materials in million ton quantities had to be moved across Rapture, first as raw materials, then after processing to work sites miles away. It took years and many trains with many traincar loads moving day and night to move such quantities. Quite believable that many parts of the original AE were pretty well worn out in this process. Other construction materials (and the workers) were likewise transported, but the concrete was by far the largest cargo. The railroad was rebuilt (Mk1 -> Mk2 around 1950 ) and carried even larger concrete material loads to finish building the City.
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Rapturooski - Engineering, Da ! - Fantasy, Nyet !!! :
Glass fiber and/or Stainless Steel Fiber added to concrete to increase Tensile Strength ( ontop of alot of water-corrosion-sealed Rebar reinforcement ). This additive mostly keeps stress cracks from forming while the concrete is setting, which helps make it set with maximal strength. Yes, Rapture WAS after all mostly concrete.
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Cement and Concrete Work :
'Cement' usually composes 10%-15% of 'concrete', and even that portion percentage meant huge volumes of the material was needed to build the City.
* Hydraulic dredges were used to remove the loose sand and other materials down to bedrock. Sand pumps sent the materials to a sand processing unit to recover sand usable for the concrete.
* Just like was done on Hoover Dam, large chunks of solid stable rock (called "Plumstones") were embedded in the Foundation concrete to fill out the mass without wasting as much cement.
* There is a aggregate crushing plant that was used to generate all the 'gravel' added to the cement to make the concrete.
* Rock from the Tunnel cutting machine might also used ( and it was found to be simpler to use as a source over the in-ocean water operations ). The Tram system was used to move the gravel and rock to the construction sites.
* There is a quarry for the 'Plumstones' on Mt Ryan of the appropriate type of igneous rock required.
* Some building have an appreciable amount of inhabitable Volume within their Foundation, as it was cheaper to build the solid concrete structure than the windowed structure ( which was pretty pointless for industrial and manufacturing facilities ). Many of the industrial building use this technique ( who needs alot of 'windows' for a refinery ?? )
* The Earliest Geothermal power generation units in Rapture were built to power much of the construction equipment and the habitats for the construction crews.
* Trams moving thru Tunnels criss-crossed the city to provide the needed bulk transportation ( more convenient than subs for everything ).
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Rapture Was Largely Concrete - and Concrete Needs REBAR :
( Reinforcement Bar )
Metal is far to expensive for it to make up more than a tiny portion of the building wall structure in Rapture. So mass Concrete would be the obvious PRACTICAL solution - utilizing that materials significant compression strength. Distributing the tensile stresses of the vast force from the ocean water across a structure requires the Concrete be reinforced.
Stainless Steel Rebar ( ordinary steel corrodes quickly in salt water/high-pressure environment ) : It Costs about 3 X as much as ordinary steel Rebar ( and there is alot of Rebar in proper reinforced concrete ). Additional coatings/platings can be employed to try to prevent the expected corrosion ( would advance as several years went by, and the added expense may explain why later construction was of the 'tunnel' type ).
Aluminum Rebar ( costs about 2 X steel then, about the same as it costs now ).
Basalt Rebar - made from remelted volcanic rock, so has a potential local material source, and likely to be used on later Rapture construction. Costs about 5 X of Steel Rebar ( BUT with less transport costs ).
Micro Rebar ( fine wire sized, used as a filler mixed in the concrete ) - again is subject to corrosion.
Various Mineral Fiber additives to concrete to minimize/counter internal stresses while the cement sets ( Real World this is a major factor in concrete strength ).
Strength of the aggregate likewise is important for strength ( good selection and preparation of it likewise ).
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Hydraulic Concrete - Concrete Cement which cures UNDERWATER ( needed at least in part for Rapture's Construction ).
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Better Concrete : 
The RIGHT Formulation of Concrete ( with timely placement and careful mixing/handling ) is needed to meet the strength requirements for deep water structures. With surface pre-construction, sea-compatible hydraulic cement need not be used there, allowing MUCH BETTER cement application properties.
As much construction as possible would be done to maximize efficiency/quality and to minimize expense/construction-time
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Mass Concrete Strength 10 MPa->50 MPa (MPa = Mega-Pascals)
10MPa = 1450 lb/sq in (Psi) means 1 sq inch can withstand (hold up) 5 sq in of external surface at ~600 ft depth ( 280 Psi water pressure ). Means 20 % of the Building's Internal Structure volume must be the Concrete Support Structure ( We need even more game represented thickness in the buildings graphics skinning and '3D' meshing ).
If the concrete strength is 50 Mpa, then its support component ratio would be 1 in 25 ( Consider the (old) normal 300% engineering margin, which might be far higher in Rapture when building things in that hostile/difficult environment ).
Steel in Rebar metal - its Tensile Strength is 140–160 MPa - and 250 typical up to 420 MPa ( specialized/expensive alloy material ).
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Vapor Barriers for Concrete :
Concrete sweats water/dampness - Also there is Cold wall condensation.
There would be false walls with 'collectors' on the INSIDE of external 'cold' walls - with drainage to sumps lower in the building ( using gravity flow ), and the necessary pumping apparatus ( back out into the ocean - high pressure pumps working against the ~280 lb/sq in ).
Cold external surface assists in dehumidifying air.
Maintenance needs to be able to get to these collectors to handle the mold/dirt that is likely to form there. This will probably be one of the 'Tasks' in the MMORPG for the Player to do.
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This is one thing that happens when too much compression force damages a reinforced concrete pillar. Note the amount of Rebar ( steel reinforcement bar ) in its volume, which has the property of Tensile strength meant to resist sideways Shear and Tensile forces, which concrete by itself is weak in resisting. 
But like anything, if you put enough force of any kind onto a structure, IT WILL FAIL.
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Real reinforced concrete building ( not steel girders - building isn't that tall to require it ). Building built in 1950 being torn down. Look how thin the flooring is ( and lots of Rebar ). Walls supported largely by pillars and large windows. Center utility core (and staircases etc ... ) still takes up space. Buildings Low structural weight is all that needs to be supported against gravity ( no huge pressure on outside walls to withstand ). 
Opposite of Rapture's Construction, which being subject to immense OUTSIDE water pressure, would have small windows, very thick walls/top, quite thick floors to act as horizontal distribution of the force on the external walls ( across to the opposite wall ).
Such a limited number of stories still is plenty of 'tall' WHEN you stand in proximity to it ( No dim 60+ floors on a pencil thin building ala those Rapture 'artist' conceptions - AND what's seen in Skybox views of Rapture's cityscape ).
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Pillars with a structural 'Fillet' to spread the force ( increasing diagonal support )
Rapture would make use of these (often hidden in a false ceiling) -- as the force due to external water pressure is extreme.
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Two Problem of the 'Setting' of Concrete : Shrinkage, And Heat Buildup Causing Stresses :
Large masses of concrete have an internal heat buildup problem from the chemical reaction of the setting cement. That heat can cause a great deal of structural defects in the material.
The Concrete also shrinks as it solidifies. This shrinkage causes Tensile Stress that introduces defects (ie -large cracks) as a result. This stress happens especially when it is poured in large blocks. 
Hoover Dam, which WAS largely on big mass of Concrete, was built up (cast/poured) in cells to minimize extending shrinkage ( The cracks between these cells were then systematically patched with 'grout', as the damn grew ). The Dam's Construction also had a system of small pipes systematically installed (in the blocks of concrete) through which cooling water was circulated for years after it was finished -- to alleviate the heat built up as the concrete slowly set. 
Pre-Fabrication on the Surface would assist in minimizing complications of this sort - much better control of the environment and methods of alleviating the problems of large chunks of Concrete for Rapture's buildings.
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REAL WORLD Concrete Monstrosities :
"La Coupole" - a Massive WW2 Nazi Concrete Installation, Built to be an Underground V2 Base ( for assembly and launching ) :
Part of My What Else Was This Big comparison of Concrete Structures.
* Reinforced Concrete
* 71 meter diameter (233 ft wide) dome of 5 Meters thick steel-reinforced concrete
* Chamber underneath is 33 meters high (108 ft)
* 55,000 tons of Concrete 
Unfortunately for the Nazis, the complex was built in a rock formation of chalk, which when the Allie's bombs (biggest they had) couldn't do anything significant to that thick Concrete, but the bombs still were able to destroy adjacent underground facilities ( penetrating the soft chalk rock ), and so nullified the whole project. The Nazis then shifted to portable V2 Missile launchers.
Such chunks of concrete I use as a measure of how difficult it would be to build Rapture ( also taking into account it is ~600 feet underwater, and in the middle of the North Atlantic ). That's why I would have Rapture's construction projects do ALOT of their (original) building On or Near the ocean surface whenever possible ( thus being mostly prefabs lowered to the ocean floor ).
Likewise, there were many difficulties for the Nazi's - It was late in the war with all the labor/material shortages, and trains being bombed, impairing operations.
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Another :
177000 cubic feet of Concrete went into Goering's Bunker ( built next to "Berchtesgarden" or "Wolfs Lair" ? )
All that Concrete used by the Nazis - Ryan's Agents went to inspect -- Even to maybe go pick up a few (now available) 'experts' ( a good backstory for the MMORPG ).
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Hoover Dam !!! 
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I have very hot water being transported in large concrete pipes across Rapture from Hephaestus to heat much of the City.
Concrete DOES NOT like Salt. Most Metal ( usual material for Rebar ) also does not like Salt.
Sea Water has all kinds of other corrosive chemicals in it as well ( now increased by the near boiling point temperatures )..
Some kind of neutral lining would be desirable for this heating pipe network.
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