Asphalt concretes

Question 1

What is the composition of asphalt concretes?

Answer 1

> ASPHALT CEMENTS + aggregate
high MW HYDROCARBONS: distillation byproduct from making crude oil
thermoplastics, above Tg they are NEWTONIAN FLUIDS, below Tg VISCOELASTIC SOLIDS

Question 2

How are asphalt concretes used?

Answer 2

> for HOT-MIXED CONCRETES: cement/aggregate is heated well above asphalt Tg
it is compacted >90% of its theoretical maximum density

Question 3

How are asphalt concretes compacted?

Answer 3

> using self-propelled steel-wheeled or pneumatic rollers

Question 4

What happens above Tg?

Answer 4

> cement acts like a lubricatn, aaslssisting in re-positioning the aggregate into denser configurations

Question 5

Why is asphalt paving restricted to summer months in some countries?

Answer 5

> to prevent prematrue cooling prior to compaction

Question 6

What’s a cutback?

Answer 6

> asphalt cement is first combined with a solvent (gasoline or kerosene) to form a fluid “cutback”, which is cold-mixed with aggregate and placed and consolidated like hot mixed concrete.
hardening occurs as solvent evaporates
not used due to health concerns