Monday, 7 October 2013

Three materials: Concrete, Steel and Marble

Concrete
Method: Concrete is made using a mixture of water, cement, lime and agrigants which can then be cast into any shape using a skin which can then be taken away once the concrete hardens. Concrete is a composite material composed of coarse granular material embedded in a hard matrix of material that fills the space among the aggregate particles and glues them together
life: Without maintenance typically engineered to last 60 years
Weakness: water corrosion, chemicals, vegetation, temperature
Structural positives: very good under compression, durable, reliable
Structural negatives: Heavy, brittle, water degradation. As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensile and compressional loads. Concrete structures without reinforcing, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally.
Use:Mostly used for compression structural elements and support for building. very good resistenace to fire and smoke, thus is used in fire escapes for facilities. Concrete can be seen as an articfical sedimentation rock.
impact: Impact on the development of structure has be exponential, making things possible that wouldn't have been without it. Economically, concrete is quite cheap to manufacture as its different components can be locally sourced making its cost minimal for materials as well as transport. Environmentally, concrete can have terrific effects on the environment espcially in the case of a natural disaster.

brick and reinfoced concrete 



Steel/ metal
Method:The open-hearth furnace is one way to create steel from pig iron. The pig iron, limestone and iron ore go into an open-hearth furnace. It is heated to about 1,600 degrees F (871 degrees C). The limestone and ore form a slag that floats on the surface. Impurities, including carbon, are oxidized and float out of the iron into the slag. When the carbon content is right, you have carbon steel.
Life: It is a long lasting material (buildings, rail lines, bridges) and resistant to wear (machines and equipment). Stainless steel is said to last for uptom1000 years without proper treatment. 
Weakness: Bends easily under compression.
Structural positives: it is very strong and resistant to fracture (building frames, security doors, trains, ships). Steel is very good for reinforcing concrete and is very good for earthquake zoned areas as it is flexible and not ridged or brittle. very attractive when polished. Stainless steel doe snot rust.
Structural negatives: High initial cost, difficult to fabricate, difficult to weld, difficult to polish(however has a very attractive polished look)
use: Steel can be used to reinforce, in compression, for building skeletons and frames, to support cantilevers and for most other structural elements for buildings.
Impact: The methods used to create steel use high amounts of energy to create and so highly impact the environment. Steel is quite expensive to produce and construction tries to minimize the amount of steel needed to perform a job.



Marble
Method: Marble is a non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Geologists use the term "marble" to refer to metamorphosed limestone; however, stonemasons use the term more broadly to encompass unmetamorphosed limestone. Metamorphism causes variable recrystallization of the original carbonate mineral grains. The resulting marble rock is typically composed of an interlocking mosaic of carbonate crystals. Primary sedimentary textures and structures of the original carbonate rock (protolith) have typically been modified or destroyed.Marble is commonly used for sculpture and as a building material.Marble is quarried from areas that it is located in. Blocks are cut from large seams of marble in quarries, which are basically open pit mines. Marble is formed by metamorphism under heat and pressure of limestone.
Life: On average marble has a very long life span and it is not said what the exact time periord for which the marble components start to break down, however, marble, if left unprotected and maintained can last up to 100 years, from which weathering and heat changes can begin to crack or disrupt clean polished veneer. .
Weakness: very Brittle, easily scratched,
Structural positives: Highly weather resistant, hard and very attractive in most cases. resistant to most chemicals and acids.
Structural negatives: brittle, expensive, easily scratched.
Use: For sculpture, tiling, structure, and other various decorative elements. However marble is mainly used for finished appendages, the number of projects using marble purely as a structural material is minimal.
impact: Quarries have a large effect on the environment and often destroy alot of the local landscape and ecosystems that are directly effected by each mine. marble is not normally a locally sourced material and so high levels of energy are used to transport marble blocks from different sites.


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