masonry, bricks, glass and wood

Question 1

whats masonry composed of

Answer 1

clay, shales, concrete bonded together in blocks held together with mortar

Question 2

pros of masonry

Answer 2

1-locally available stones can be used
2-HIGH THERMAL MASS (insulation)
3-durable
4-high fire resistance

Question 3

cons of masonry

Answer 3

1- heavy-need strong foundations
2-flexural strength limited
3-not good for earthquakes

Question 4

modern masonry

Answer 4

-fly ash and concrete(cinderblocks)

lightweight

Question 5

whats dry stone and whats it used for

Answer 5

Interlocking stones to make walls-housing, , v durable

Question 6

whats the compressive strength of a brick

Answer 6

100MPa

Question 7

how is the load transfered in bricks

Answer 7

down the courses, which are not aligned vertically

Question 8

Brick making- decribe the heating process

Answer 8

• clay, sand and water mixed and heated to 1000 degrees
• 490 degrees- water lost
• 980 deg transformation from clay minerals to glass and crystalites

Question 9

whats the difference between soft and hard mud stones

Answer 9

• soft mud- higher water content 25-30%, varying strength

- hard mud_8% water, better quality but more expensive

Question 10

2 problems that occur with bricks

Answer 10

• efflorescence- water seeps through, evaporates and leaves white precipitate/salt on surface
• water absorbs on to surface, freezes, expands and brick face crumbles(frost heave?)

Question 11

formation of glass vs crystals

Answer 11

glass- super fast cooling

grustals super slow

Question 12

whats the glass transition temp

Answer 12

the temp at which it transitions form hard to soft- reversable, brittle to viscous

Question 13

Describe the float glass process

Answer 13

1-melting of materials
2- float area where it levels out on a pool of tin as less dense
3- annealing leur-cooled slowly to remove internal stresses and toughen it

Question 14

discuss the strengths of glass

Answer 14

brittle-20-100MPa
weak in tension, stronger in compression
- static fatigue-h20 attacks on bonds in cracks makes it weaker under long term loading

Question 15

how is toughened glass made- give an example

Answer 15

• heat it to above the tg
• then quench the surfaces, putting them in compression and the centre in tension, strenghtening surface
• eg prince rupert drops- molten glass in to ice cold water, tensile region up the tail, this cracks it all shatters

Question 16

whats gorilla glass

Answer 16

-ION EXHANGE

putting larger ions K, in to spaller ion places (Na) gives compressive forces, as its squeezing in, strengthens surface

Question 17

whats laminated glass

Answer 17

polymer films between sheets of glass

Question 18

bullet proof glass

Answer 18

layers of POLYCARBONATE laminate between glass layer-interfaces stop crack passing all the way through

Question 19

list and describe the 4 engineered pieces of wood

Answer 19

1-fibre board(MDF)-wood fibres chemically separated and pressed together with resin
2-particle board-small chips of wood pressed together with resin
3-plywood-layers alligned with crossed grains glues together
4-glulam- glue laminated timber
(in increasing size)

Question 20

which direction in timber stronger in under tension

Answer 20

Stronger in tension parallel (50-120 mpa) to the grain than perpendicular (<5mpa)

Question 21

after wetting and drying, in which directions are the changes mire drastic (humidity)

Answer 21

tangential (3%)

radial(1%)

Question 22

describe what creep is

Answer 22

wood under sustained load
-cells compressed, fibres slip
can be reversible or irreversible

Question 23

list 3 resins and state the pros and cons

Answer 23

1-urea formaldehyde-not waterproof
-cheap
-carcinogenic when formaldehyde degrades
2-phenol formaldehyde- water resistant,spenny
3-polyurethane- water resistant
-more expensive, non carcinogenic