Composites 2

Question 1

Is concrete a composite?

Answer 1

yes

Question 2

What is filler is concrete made out of?

Answer 2

Aggregate- rock and sand

Question 3

What matrix is concrete made out of

Answer 3

Cement

Question 4

What percentage of concrete is aggregate?

Answer 4

70-80%

Question 5

What is the purpose of sand in aggregate?

Answer 5

Fills voids to reduce porosity

Question 6

How does concrete set

Answer 6

Cement undergoes a cementation reaction

Question 7

What is the water used for in cement

Answer 7

incorporates into the structure

Question 8

Main minerals (C)

Answer 8

CaO

Question 9

Main minerals (A)

Answer 9

Al2O3

Question 10

Main minerals (F)

Answer 10

Fe2O3

Question 11

Main minerals (S)

Answer 11

SiO2

Question 12

Density of concrete

Answer 12

2 gcm3 (dense)

Question 13

(L/H) concrete fracture toughness

Answer 13

L

Question 14

(L/H) concrete tensile strength

Answer 14

L

Question 15

Why is concrete used?

Answer 15

Cheap and good compressive strength

Question 16

Why does concrete get better with age

Answer 16

Cementation reaction still taking place

Question 17

What does the strength depend on in concrete?(2)

Answer 17

Minerals and amount of water

Question 18

Pro of adding more water to your concrete

Answer 18

Makes concrete more workable

Question 19

Con of adding more water

Answer 19

As it increases shrinkage it makes cracking more likely

Question 20

what is reinforced concrete

Answer 20

concrete with steel rods

Question 21

What is pre-stressed concrete?

Answer 21

Steel rods under tensile stress while concrete is pored

Question 22

Con of steel reinforced concrete

Answer 22

water rusts steel making it expand and create cracks

Question 23

Why is concrete so bad for the enviroment

Answer 23

Only cause so much produced, actual production is quite low co2

Question 24

Why would you use wood?(5)

Answer 24

Cheap, strong, lightweight, aesthetics, eco friendly

Question 25

Structure of wood - Fibre

Answer 25

Lignin holds cellouse fibres and hemicellulose together in same direction

Question 26

Structure of wood - cell structure

Answer 26

Made of cells with microfibril facing different ways in each layer

Question 27

structure of wood- macrostructure

Answer 27

Long unidirectional polymer cells

Question 28

Why is softwood less dense

Answer 28

Has more hollow cells for transporting water

Question 29

Can wood float on water

Answer 29

yes

Question 30

What effects wood strength

Answer 30

direction of cells

Question 31

Does wood have good compressive strength

Answer 31

no

Question 32

Which type of wood does wood densification use?

Answer 32

Soft wood

Question 33

How does wood densification work?

Answer 33

Uses chemicals and heat to remove lignin and hemicelluloses

Question 34

Why densify wood?

Answer 34

Outperforms in specific strength, energy to manufacture and cost