Week 2: 3 Materials

Choose three materials and do some research on their properties, i.e. the process of making each material, how long they will last, what makes them corrode, structural pros and cons, what these materials are typically used for, environmental impacts.

CONCRETE

Concrete is a mixture of two components: aggregate and paste.

Aggregates: sand and various sizes of gravel and crushed stone. Fine aggregate: 5mm or less. Course aggregate: up to 40mm.
Paste: limestone + clay + gypsum + various other chemicals and minerals = cement. These materials are crushed, mixed in appropriate proportions, burned and ground. Resulting mixture is combined with water where a chemical process called hydration takes place, and the resulting paste dries into a solid stone-like mass.
Cement, water and aggregate measurements have a huge influence on concrete's strength, permeability and durability.
Lifespan: depends on iron and steel bar reinforcement inside. When air, moisture, and chemicals seep into reinforced concrete, the bar rusts, expanding in diameter four or five-fold, which destroys the surrounding concrete. Usually 70-80 years.
Pros: economical when ingredients are readily available, long life, low maintenance requirements, unlikely to rot, corrode, or decay, molded or cast into any shape, non-combustible material, withstand high temperatures, resistant to wind, water, rodents, and insects, often used for storm shelters
Cons: low tensile strength, low ductility, low strength-to-weight ratio, susceptible to cracking
Decay: harsh weather, decay of connected materials (eg steel), physical destruction

GLASS

Primary ingredient: silica/quartz sand without iron impurities as the iron will cause the glass to appear greenish when present.
Other ingredients: sodium carbonate, calcium oxide, magnesium/aluminium oxides. Sodium carbonate lowers temperature necessary to make glass commercially. However, it permits water to pass through the glass, so calcium oxide, is added to counter this. Magnesium/aluminium oxides may be added to make glass more durable. These make approximately 30% of ingredients.
Chemicals: chemicals can be added to produce desired colours. Iron/copper oxide can be added to create a green effect. Sulfur compounds create yellow, orange, brown or black effect, depending on how much carbon or iron is included.
Mixture is melted into liquid. Commercial silica is melted in a gas-fired furnace. Without additives becomes glass at a temperature of 2300 degrees Celsius. Sodium carbonate lowers required temperature to 1500 degrees Celsius. Stir mixture to make it even and get rid of bubbles.
Molten glass is poured into a bath of molten tin for support and blasted with pressurized nitrogen to shape and polish it. This is how glass panes are made.
Annealing: heat treat glass to strengthen and remove stress points that formed during cooling. Then the glass is treated to improve strength and durability.
Glass lifespan: approximately 40 years
Decay: harsh weather, erosion, physical destruction

MARBLE

Large cubes of marbles are extracted from the ground.
Piece is loaded on platform supported by hydraulic lifts that lift marble into steel saw blades slicing from above.
Slab is placed face down and diamond-encrusted abrasive pads grind the surface to smooth the material. It is then sprayed with epoxy sealer and left for 48 hours. This is then repeated on the other side of the material.
Decay: chemical reactions (weather), physical destruction