Bituminous Materials

Question 1

What are bituminous materials

Answer 1

Materials that are hydrocarbon based
and are used as binders in construction

Question 2

What does it mean that bituminous materials exhibit viscoelastic behavior

Answer 2

They behave as both a solid and a liquid depending on temperature

Question 3

What are some applications of bituminous materials

Answer 3

Roads, waterproofing, roofing, industrial coatings

Question 4

What is bitumen and what are the two sub categories

Answer 4

Bitumen is a black, extremely viscous sticky liquid
and is broken up into tar and bitumen
Bitumen is soluble in petroleum
and tar (macadam) is resistant to it

Question 5

What are some properties bituminous materials provide

Answer 5

Strong adhesion to aggregates
Waterproofing
Flexibility to accommodate temperature variations and help in load distribution

Question 6

What are some types of bitumen binders

Answer 6

Asphalt
Tar
Cutback bitumen
Bitumen emulsions

Question 7

How is asphalt binder made and what are its properties/uses

Answer 7

Used in road construction
derived from petroleum refining
high durability and adhesive properties

Question 8

How is tar binder made and what are its properties/uses

Answer 8

By product of coal distillation
More temperature sensitive that other bitumen binders
Not used as much due to health and environmental concerns

Question 9

How is cutback bitumen binder made and what are its properties/uses

Answer 9

Regular bitumen cut with volatile solvents such as kerosene and naphtha
Used for cold weather applications but less environmentally friendly

Question 10

How is bitumen emulsions made and what are its properties/uses

Answer 10

Bitumen mixed with water and emulsifiers
Used for cold weather applications but more environmentally friendly that cutback bitumen

Question 11

What are the sources of bitumen

Answer 11

Lakes
Rock asphalt
Oil sands
Derived from crude oil

Question 12

What is the makeup of bitumen

Answer 12

80-87% carbon
8-11% hydrogen
Small amounts of sulfur, oxygen and nitrogen

Question 13

What is the viscosity of bitumen compared to water

Answer 13

Bitumen has an extremely high viscosity and is 230 billion times that of water

Question 14

What is PEN value and what is it for most UK roads

Answer 14

PEN value is a measure of how ‘stiff’ the material is
and is measured by a force of 100g pushing on a needle for 5 seconds and seeing how far it travels into the material
Most UK roads are between 50-200 PEN

Question 15

What are the names of the different layers in a roads construction from top to bottom

Answer 15

Surface course
Binder course
Base course
Foundation Layer

Question 16

What is the function of the surface course

Answer 16

Provides rut and water resistance
Flat to provide ride smoothness
Skid resistant
Low noise creation

Question 17

What is the function of the binder course

Answer 17

Provides structural stability
and acts as a regulating course

Question 18

What is the function of the base course

Answer 18

Main load spreading layer
and has high stiffness and deformation resistance

Question 19

What are the constituent pieces of asphalt

Answer 19

30-70% course aggregate
20-40% fine aggregate
<7% filler
4-7% bitumen

Question 20

What does the bitumen provide in asphalt

Answer 20

Lubricant
Waterproofing
Aids stiffness

Question 21

What is PSV and why is it important

Answer 21

Polished Stone Value, is the resistance the aggregate has to polishing under traffic
Lower PSV means more skid hazards in the long term

Question 22

What are some additives used in asphalts

Answer 22

Color pigments
Fuel resistants
Workability enhancers
Flux for when being layer cold

Question 23

What are the 3 main types of asphalt

Answer 23

Hot rolled asphalt
Asphaltic concrete
Stone mastic asphalt

Question 24

Describe hot rolled asphalt

Answer 24

Dense and durable course using pre coated chippings at the surface which gives a positive texture

Question 25

Name and describe the three types of asphaltic concrete

Answer 25

Three types of asphaltic concrete (AC) are: dense graded mix, open graded mix and gap graded mix. Dense graded: well graded, low air voids, high strength and durability Open graded: 15-25% air voids to allow more water drainage and improve skid resistance Gap graded: discontinuous grading meaning that medium sized aggregates are missing which increases flexibility and resistance to cracking

Question 26

Describe stone mastic asphalt

Answer 26

An asphalt type which uses gap grading asphaltic concrete

Question 27

What are hot and cold mixed asphalts

Answer 27

Hot mixed asphalts (HMAs)-produced at 150-180°C, requires lots of energy but provides maximum strength and durability Cold mixed asphalts (CMAs)-produced at ambient temperatures using emulsion bitumen, lower cost and can also be laid in wet conditions so good for emergencies

Question 28

What are the advantages and disadvantages of HMAs

Answer 28

Advantages: quick construction compared to concrete, high durability, flexibility, and recyclability Disadvantages: temperature sensitive, high cost and has environmental consequences during production

Question 29

What is batch and drum mix types

Answer 29

Batch mix- small controlled amount of mix used for custom mixes and small projects Drum mix- continuous production used for larger projects but less opportunity for customization

Question 30

How must bituminous materials be stored and transported

Answer 30

Stored- in heated silos to keep mix at proper temperature and contamination must be prevented to stop oxidation and other premature aging Transport- must be held in heated tankers to prevent solidifying and maintain workability

Question 31

What is spreading and rolling in paving

Answer 31

Spreading-material is spread out for a uniform thickness Rolling-steel, pneumatic and vibratory rollers passed over for compaction, density adjustments and void reduction respectively

Question 32

What is rutting

Answer 32

Depressions in wheel paths caused by poor mix design and continued overloading

Question 33

What is ravelling

Answer 33

Loss of aggregates from the surface due to aging or poor bonding

Question 34

What is stripping

Answer 34

Moisture weakens the bond between bitumen and aggregates, often leads to raveling