Materials Flashcards
Steel is made out of ?
0.3% carbon , developed by melting of coke, limestone and iron ore. Carbon is removed by heating and adding oxygen.
Two forms of timber are and produced from
Hard wood and softwood, Hardwood is deciduous trees while softwood uses coniferous trees
Common preservative added to timber is known as
tantalizing
Corrosion of steel is prevented using the process of
Galvanising, which involves passing steel through molten zinc , which is when oxides will form surface layer or Electro galvanising involving depositing zinc on surface via electroplating.
What is formwork
A mold from which concrete is cast.
How is formwork done?
Form is made from timber, releasing agent is applied to surface of formwork before the slurry is poured, concrete must be vibrated in order to remove air bubbles by bring them to surface.
Explain reinforcement in concrete
Concrete can be either cast insitu or in factory (precast) . Material must be reinforced with steel bars for it to withstand tensile stresses. Size and distribution of stresses are redistributed with these steel bars which are formed as cage.
What is prestressed concrete
For spans over 8m its advisaboe for reinforcing bars to be tensioned. principle is similar to horizontally applying pressure and lifting them at the ends of the row. With concrete this can be done either by pretensioning or post tensioning steel reinforcement.
What is slurry
Consist of aggregates (fine:sand , coarse:stone) , binding material (cement) and water.
Self compacting concrete?
This is freeflowing liquid concrete that flows freely into moulds and around steel reinforcement and fully compacts without need for additional vibration. It contains additives known as plasticizers which leave a glass-smooth surface.
What ways are glass toughened?
Annealing , Tembering/toughening , Laminating.
What is Annealing?
controlling rate at which molten glass cools, the stresses and strains that normally occur due to shrinkage during cooling is removed
What is tempering?
Glass is reheated and surfaces rapidly cooled with jets of air. inside core of glass continues to cool and contract forcing surface into compression and core tension. when glass breaks the core realises tensile energy resulting into formation of small glass particles.
Laminating?
glass is bonded together in layers with resin in between to form a composite. if outer layer breaks it is held in place by substrate. Structural glass beams typically consist of three layers laminated together for safety reasons.
Explain why Laminated glass is used in in facades and beams?
Because of its three layered properties. Structured glass beams are connected to columns using bolts, silicon glue. Structural glass is also used for ribs and fins fixed perpendicular to panes in order to resist wind load on glass facades.
