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CIVI 321 > CHAPTER9 > Flashcards

CHAPTER9 Flashcards

1
Q

Behaviour of asphalt binder according to temperature

A

high : viscous

low : elastic

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2
Q

The characteristics of asphalt binder depends on

A

temperature and loading rate

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3
Q

3 types of asphalts used in pavements

A
  • asphalt cement
  • asphalt emulsion
  • asphalt cutback
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4
Q

what is asphalt cement used for

A

HMA and patching

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5
Q

what is asphalt emulsion used for

A

cold mix & maintenance

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6
Q

what is asphalt cutback used for

A

cold mix & maintenance

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7
Q

characteristics of asphalt cement (binder)

A
    • adheres well to most rock
    • waterproof
    • fairly durable
    • resistant to rxn w most acids, alkalis & salts
    • temperature sensitive (semi solid @ room temp)
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8
Q

what is asphalt cutback

A

asphalt cement + cutback

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9
Q

characteristics of asphalt cutback

A
    • hazardous and volatile hydrocarbons are released
    • cold mix maintenance, patching, chip seals, crack sealing, base and sub-base stabilization and surfacing low volume roads
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10
Q

what is asphalt emulsion

A

asphalt cement + water + emulsifying agent

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11
Q

asphalt emulsion is similar to _____ in its uses

A

asphalt cutback

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12
Q

advantages of asphalt emulsion over asphalt cutback

A
    • safer
    • environmentally better
    • cost?
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13
Q

what is asphalt concrete?

A

asphalt binder + aggregate

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14
Q

what is asphalt binder used for?

A

sealing and waterproofing

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15
Q

what is asphalt concrete used for?

A

HMA pavement surfacing

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16
Q

describe the temperature susceptibility of asphalt

A

graph : log temperature (x) vs log viscosity (y). from too brittle (low temp) to too soft (high temp., low viscosity). DEGREES RANKING

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17
Q

low viscosity (soft) asphalt is used in where and for what

A

in cold climates to avoid thermal cracking

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18
Q

high viscosity (hard) asphalt is used where and for what

A

in hot climates to avoid rutting

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19
Q

Asphalt chemistry : the chemical composition depends on

A
  • the oil source

- refining method

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20
Q

asphalt chemistry : composition

A

mostly hydrogen & carbon

some sulfur, nitrogen and oxygen

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21
Q

asphalt chemistry : whats more important than what

A

the molecular structure is more important than the composition

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22
Q

4 types of asphalt grading and which one is used now?

A

PEN : penetration grading
AC : viscosity grading
AR : aged residue grading
PG : performance grading (USED NOW)

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23
Q

what was created after the SHRP and define

A

Strategic Highway Research Program : creation of the superpave & performance grade binders

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24
Q

what is superpave + define

A

Superior Performing Asphalt Pavements

it’s a mix design method for asphalt concrete and a performance grading method for asphalt binder specification.

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25
Q

3 specific distresses

A
  • rutting
  • fatigue cracking
  • thermal cracking
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26
Q

3 specific aging conditions

A
  • unaged
  • construction
  • long term
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27
Q

define PG

A

intended to improve pavement performance by reducing potential to :

  • permanent deformation
  • fatigue cracking
  • low temp cracking
  • excessive aging from volatilization
  • pumping & handling
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28
Q

nomenclature for PG

A

start with PG, followed by max & min pavement service temperatures in °C. (PG52-28)

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29
Q

where is the temperature measured for PG grading?

A

high is 20 mm (3/4”) below the pavement surface.

low at surface.

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30
Q

how is PG presented?

A

6°C increments for both high and low temperatures

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31
Q

what is a dynamic shear rheometer

A
    • test complex shear modulus of binders

- - measures the resistance to shear deformation in the linear visco-elastic range

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32
Q

what data is taken for climate values?

A

2 stdv on each side

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33
Q

how are asphalt cutbacks graded?

A

RC : rapid curing (5-10 minutes)
MC : medium curing (few days)
SC : slow curing (few months)

higher grade for viscosity is more viscous

example : RC-70 or MC-3000

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34
Q

cutback nomenclature

A

MC-viscosity number

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35
Q

emulsion vs cutback : define

A

emulsion is preferred over cutback

    • safer
    • used with damp aggregates
    • slightly more economic
    • environmentally better
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36
Q

grading for asphalt emulsion

A 
RS = rapid setting (5-10 min)
MS = medium setting (several hours)
SS = slow setting (few months)
37
Q

what is anionic

A

negative charge

38
Q

what is cationic

A

positive charge

39
Q

emulsion nomenclature

A

CMS - 1h

first : C = cationic, HG = high float
second : medium, rapid or slow set
# : emulsion viscosity
third : hard asphalt residue or soft asphalt residue

40
Q

what is HMA

A

asphalt binder + aggregates

41
Q

HMA desirable properties

A
    • stable (resists permanent deformations under load)
    • fatigue resistant (under repeated loading)
    • resistant to thermal cracking (due to contraction at low temps)
    • resistant to hardening or aging (during production and in service)
    • resistant to moisture induced damage (stripping asphalt from aggregate)
    • skid resistant (by texturing surface)
    • workable (ease of mixing, placing, compacting)
    • economical
42
Q

3 steps for asphalt concrete mix designb

A
  1. selection of design aggregate structure
  2. selection of design asphalt content
  3. evaluation of moisture sensitivity of mix
43
Q

whats included in the selection of aggregate structure for the asphalt conrete mix design?

A

preliminary (gradation and consensus properties)
and
volumetric analysis of mixes

44
Q

whats included in the selection of design asphalt content for th asphalt concrete mix design?

A

volumetric analysis of design aggregate structure at four binder contents

45
Q

lab specimen preparation, 7 steps

A
  1. grade + weight aggregates & determine target asphalt content
  2. heat & mix aggregate and asphalt binder
  3. short term aging
  4. place material into mold & apply compactive force
  5. allow to cool and extrude from mold
  6. determine specific gravity + air voids
  7. mechanical tests
46
Q

2 different types of compaction for AC mix design methods

A

superpave design mix : gyratory compactor

marshal mix design : marshall hammer

47
Q

whats in the phase diagram?

A

gas – air
liquid – binder
solar – aggreagte

48
Q

Specific gravity provides ____ b/n ____ & ____ properties of the ______.

A

Specifica gravity provides bridge b/n mass & volume properties of the hot mix.

49
Q

volumetric code names nomenclature

A

X_12

50
Q

steps for superpave mix design

A

a) aggregate selection
b) binder selection
c) determine design aggregate structure
d) determine design binder content
e) evaluate moisture susceptibility

51
Q

a) aggregate selection. stockpiles are evaluated for

A
  • soundness
  • toughness
  • deleterious materials
52
Q

what are the blend requirements for the aggregate selection?

A
    • coarse aggregate angularity (min)
    • fine aggregate angularity (min)
    • flat & elongated particles (max)
    • sand equivalency (need clean aggregates)
    • gradation 0.45 power chart (must pass through control points)
53
Q

coarse aggregate angularity minimum requirements ____ as traffic increases

A

coarse aggregate angularity minimum requirements increase as traffic increases

54
Q

why is the gradation called 0.45 power chart?

A

y : percent passing, from 0 to 100

x : sieve size, mm (raised to the power 0.45)

55
Q

define

c) design aggregate structure

A
    • evaluate three aggregate blends
    • estimate asphalt content
    • design aggregate structure (trial specimens w different aggregate gradations using gyratory compactor + uncompacted samples measure max theoretical specific gravity + volumetric analysis)
56
Q

prepare design aggregate structure specimens

A
    • for each of the three design aggregate structure blends.
    • compact 2 or 3 samples using the superpave gyratory compactor
    • prepare one sample to measure max theo specific gravity
    • perform volumetric analysis
57
Q

define VTM

A

voids in total mix

58
Q

define VMA

A

voids in the mineral aggregate

measure of the asphalt film thickness (controls the minimum asphalt content)

59
Q

define VFA

A

voids filled w asphalt

percent of the VMA filled w asphalt

60
Q

define D/B

A

dust to binder ratio (percent stone passing #200, 0,075 mm)

61
Q

VTM

A

4% for mix design
4-8% for construction
>2 % of the life of the pavement

62
Q

what is DAS

A

design aggregate structure

63
Q

define d) design binder content

A

prepare samples at four asphalt contents :

P_b -0.5
P_b
P_b + 0,5
P_b + 1.0

    • perform volumetric analysis
    • plot volumetric analysis vs asphalt content
    • select P_b w 4% VTM
    • select other volumetric param. at desired P_b
    • compare to criteria
64
Q

define e) evaluate moisture sensitivity

A
    • using DAS & DBC prepare six compacted samples (compact to specific height, 7% air voids)
    • reserve 3 samples
    • condition 3 samples (sature, freeze/thaw)
    • measure tensile strength
65
Q

what is TSR

A

tensile strength ratio =

TSR = (avg. wet tensile strength)/(avg. unconditioned tensile strength)

66
Q

what is stripping

A

loss of bond b/n asphalt & aggregate

67
Q

how to evaluate moisture susceptibility

A

2 sets of specimens : control & conditioned

  • evaluate strength before & after conditioning
  • retained strength = conditioned strength/reference strength
  • must have minimum retained strength
68
Q

how to improve moisture susceptibility

A
    • increase asphalt content
    • higher viscosity asphalt
    • aggregate clean of dust and clay
    • change aggregate gradation
    • add anti-stripping additives (liquid + portland cement or lime)
69
Q

types of AC pavement failures

A
    • rutting
    • fatigue cracking (repeated bending)
    • thermal cracking (temp. gradient)
    • excessive surface roughness (aging)
    • aging & oxidation of the binder (stiffening)
    • stripping
70
Q

the characterization of asphalt concrete is difficult because

A

AC is a nonlinear visco-elastic OR visco-elasto-plasti material

71
Q

what is a triaxial cell used for?

A

simulate vehicle loads in three dimensions

72
Q

3 tests that are still in research mode

A
  1. dynamic modulus (E*) test
  2. triaxial repeated load permanent deformation test (also known as flow number F_n test)
  3. triaxial static creep test (also known as Flow Time F_t test)
73
Q

what is the dynamic modulus test for?

A

sinusoidal load

74
Q

what is the static triaxial creep test for?

A

constant load

75
Q

3 periods for static triaxial creep test

A
  1. primary
  2. secondary (creep over time, linear portion)
  3. tertiary (flow time when shear deformations begin, all falls apart)

look for longer Flow time and long linear portion (secondary)

76
Q

what is the triaxial repeated test

A

thousands of load cycles (0.1 s load, 0.9 s unload)

77
Q

components of the AC production and construction

A
    • materials to plant
    • plant (batch or drum type, mix asphalt to required proportions and discharge to truck for haul to job site)
    • paver (place hot mix to desired thickness and smoothness)
    • compactors (achieve desired density)
78
Q

what is RAP

A

recycled asphalt pavement

79
Q

advantages of AC recycling

A
    • economy (25% savings in material cost)
    • energy savings
    • environmental
    • maintains bridge & tunnel clearances
80
Q

special considerations for using RAP

A
    • evaluate quality
    • mix design
    • production (rely on heat transfer from virgin aggregate to RAP, moisture in RAP difficult to remove)
81
Q

4 types of additives

A
  1. fillers
  2. extenders
  3. polymer modified asphalt
  4. antistripping agents
82
Q

define additives : fillers

A

crushed fines, PC, lime, fly ash, carbon black.

to improve gradation, stability, binger-aggregate bond or to fill voids

83
Q

define additives : extenders

A

sulfur & lignin to reduce amount of asphalt & therefore cost

84
Q

define additives : polymer modified asphalt

A

most widely used : SBS (styrene butadiene styrene)

high range PG binders require modification to achieve required properties.

select asphalt w required low temp. properties. use modifier to achieve high and intermediate temperature properties.

SBS improves fatigue and rutting performance

additional cost justified through better performance

85
Q

define additives : antistripping agents

A

lime, PC. improves bond b/n asphalt binder and aggregates for moisture resistance.

86
Q

define additives : others

A

fibers, oxidants, antioxidants, hydrocarbons.

to improve strength and stiffness

87
Q

warm mix : define

A

lower mixing and placing temperatures (reduction of 25-50 °C)

88
Q

advantages of warm mix

A
    • less energy required
    • lower ghg
    • less oxidation of the asphalt binder
    • pave at lower temperatures
    • longer haul distances possible
    • extending paving season since the asphalt can be compacted at lower temperatures
89
Q

asphalt binder =

A

asphalt cement

CIVI 321 (7 decks)

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