Asphalt

Question 1

three types of asphalt cements

Answer 1

cut back , emulsions, asphalt cements (normal)

Question 2

three types of cut back mix and there uses?

Answer 2

rapid cure- high volatile, sruface treatments
medium cure -stockpile patching mix
slow cure- dust control and prime coats

Question 3

when are cut backs used and why

Answer 3

when there are low temperatures, because they have higher viscosity

Question 4

what do emulsions do to asphalt droplets and how can this be used

Answer 4

give droplets surface charge, can give anonic charge making it bond well with limestone(which is positive) or catonic, positive charge making it attracted to silica gravels( which are negatively charged)

Question 5

what are the 7 types of pavement damage

Answer 5

fatigue, thermal , and transverse cracks, shoving , ravelling/pothole , bleeding , rutting

Question 6

quick explaination of each pavement damage

Answer 6

fatigue- many loads, cause tension in bottom of pavement, cracks go from bottom up
thermal cracks-shrinkage of HMA at low T
transverse-type of thermal crack
shoving- plastic movement from cars stopping starting
ravelling- dis-lodgement of aggregate, disintegration
bleeding- upward movement of asphalt, too much asphalt /hot weather
Rutting- depression caused from wheel path

Question 7

advantages and disadvantages of penetration testing?

Answer 7

fast, precision, temp susceptibility can be determined.

bad because- empirical test, does not refelct differences in asphalt…..

Question 8

grades of penetration and their uses?

Answer 8

40-50
60-70  motorways
80-100 residential streets
130-150 
180-200 liquid application

Question 9

what does the short term aging test consist of

Answer 9

Rolling thin film oven (RTFO)
tests hot mix aging by placing samples in the oven and having an air supply of 4L/min. 165 degrees 75 mins.
determine mass percentage loss (due to oxidation)
also penetration test before and after

Question 10

what does long term aging consist of

Answer 10

pressure aging vessel,

50 g sample aged for 2 hours at 2070 kpa at 100 degrees. equivalent of 7 to 10 years

Question 11

adv/disadv of viscosity grading?

Answer 11

adv- fundamental property
based on max pavement surface temperature
disadv-not applicable for non-Newtonian materials
-wide range of properties for same grade

Question 12

what are the two ways in which the temperature susceptibility is measured ?

Answer 12

penetration index (find penetration at two different temps and use equation)
viscosity temperature susceptibility (same as above but viscosity and different equation)

Question 13

list 7 objectives of mix design

Answer 13

• stability
• durability
• impermeability
• skid resistance
• fatigue resistance
• flexibility
• workability

Question 14

summary of marshall mix design method (short)

Answer 14

• use impact hammer
• determine stability with marshall stabilometer
• use volumetrics to select optimum asphalt content

Question 15

what is bulk specific gravity

Answer 15

is defined as the ratio of 
the weight in air of a unit 
volume of a permeable material (i
ncluding both permeable and impermeable 
voids) at a stated temperat
ure to the weight in air of equal density of an equal 
volume of gas-free distilled wate
r at the stated 
temperature. 
=a/(b-c)     
a dry mass b ssd mass c submerged mass

Question 16

what is difference of apparent specific gravity and previous answer

Answer 16

excludes permeable voids

Question 17

what is VMA

Answer 17

volume of void space including air voids and effective bitumen content

Question 18

what is the equation to find effective bitumen content

Answer 18

Pbe=Pb-(Pba x Ps)/100

Question 19

what is Va/VTM

Answer 19

volume of air voids

Question 20

VFB/VFA?

Answer 20

proportion of voids in aggregate filled with bitumen = Vbe/(Vbe+Vvoids)

Question 21

what are some compaction methods?

Answer 21

Impact hammer, used in marshal mix
kneading compaction used in HVEEM mix
Gyratory compaction
Vibratory hammer