HOT-MIX

GONGRETEASPHAlTIG

STATEDEPARTMENT

OF HIGHWAYSAND PUBLIC

TRANSPORTATION

CENTERFOR

TRANSPORTATIONRESEARCH

TEXASTRANSPORTATION

INSTITUTE

A REfRESHER COURSEWINTER 1982-83

HOT-MIX ASPHALTIC CONCRETE

-A Refresher Course-

by

Dr. Jon Epps

Texas Transportation Institute

Dr. Thomas Kennedy

Center for Transportation Research

Mr. Bi 11 Elmore

State Department of Highways and Public Transportation

Winter 1982-83

TABLE OF CONTENTS

INTRODUCTION (Presented by Dr. Epps).

Changing Factors.

Pavement Problems

Structural Design

Construction

Traffic.

Materials

POTENTIAL PAVEMENT MATERIALS (Presented by"Dr. Epps).

"New" Pavement Binders (Considerations).

Potential Pavement Binders

Temperature Susceptibility

Water Susceptibility ...

Field Distress Most Common

Antistrip Chemicals.

Recognition of Water Susceptibility Problems

Possible Solutions .•..........•

MIXTURE DESIGN (Presented by Dr. Kennedy)

Overall Objective of Mixture Design.

Specific Objectives of Mixture Design

Factors in Design.

Hveem Design ••

Tensile Testing.

Stiffness and Fatigue Behavior

Moisture Susceptibility Tests.

'. .

Page

1

2

3

4

8

9

10

41

42

43

54

55

56

61

62

65

70

70

71

77

81

89

95

97

TABLE OF CONTENTS (Continued)

PLANTS (Presented by Dr. Epps).

Types of Plants•••••

Operation and Inspection of Asphalt Plants

MAJOR CHANGES IN ITEM 340 (Presented by Mr. Elmore)

Skid Resistant Aggregates.

Master Gradings.

Design

Stabi lity.

Equipment.

Stockpiling.

In-Place Density

•

COMPACTION (Presented by Dr. Kennedy)

Purpose of Compaction..••..

Methods of Achieving Compaction.

Factors Affecting Compaction

Important Equipment Factors.

Temperature Influences Workability

Rolling Patterns ..•

Minimum Specifications

..

Page

109

110

127

133

133

134

134

135

138

142

146

147

148

149

150

151

152

153

154

INTRODUCTION

CHANGING FACTORS

* Structural Design

* Construction

* Traffic

* Environment

* Materi al s

2

PAVEMENT PROBLEMS

* Rutting

* Tenderness

* Water Susceptibility

* Slippage

3

STRUCTURAL DESIGN

* Thin Overlays

* Open Graded Friction Courses

* Interl ayers

. .

ASPHALT CONCRETE

BLACK BASE

BASE

5

OPEN GRADED

OLD ASPHALT CONCRETE

BASE

6

NEW ASPHALT CONCRETE

============================== Inter1ayer

OLD ASPHALT CONCRETE

BASE

7

CONSTRUCTION

* Drum Mixers

* Vibratory Rollers

* Thin Overlays

* Air Quality Regulations

8

TRAFFIC

* Magnitude of Load

* No. of Repetitions

* Tire Pressure

9

MATERIALS

* Aggregates

* Asphalts

10

I0.50.005 0.01 0.05 0.1Decimals of Maximum Size

oa=::::: --i..__.l..- --I.__.l.- ---l_---..I

0.001

30

50 1-- --+__--+-_~~~-+__-~--__.tC_....L..--+-____j

Grading /limits_....'" /

--~--.....",.4=::::::",.~'---I Hor.sh Mixture.Critical Mixtures,- I ~

8ecomes readly unstable / Inclined towith slight excess of / / Segregate;asphalt or water Not critIcal.

100 ...------,..----,------,.---"T-----........- ..........

--20 I------+~~-I-____..~_=-==+--+_-------J.-_____J:;;-- =-- Porous Mixtures;Lack tensile strength when

10 I-----o.....~--:...l-~~_:_+- mixed with road oil; ----+-----18est results with heavy bitumen

90 f---------+----I-----~--+_----__AI_~Notes opply to any

g roding curve which -----+---+-------J~t_-I-__j80tl> transgresses area.~ defined by dashed lines'" TO I------+--~---­'"l::lQ..

Aggregate morecostly to produce ;'-+'~--t,I--~Surface easy to /.finish ./

.... 601------+--+--------+-----j",L--r---~,L-t_-__jt:::It>

"'-It>Q..

Fisurc C10. Gr3ding Chart Illu:tratinn Sradino SDccific~tion: E:t~bli~hcd toAvoid Undesirable Conditions. (California Division of Highways)

IMPROVE QUALITY OF BINDER

12

,/

/

/.- .-

TEXAS

U.S.

REGION 6

I /• I

//• I

./1/1

. I

/ 11

/ 1

'"'"'"~"----------1,'.,It.,

I'. ,fr--.-:::-:;;.:::: .."..--.-

15

10

35

30

25

40

20

zo....ct::U.J0-

ct::«-'-'oo

5

68 69 70 71 72 73 74 75 76 77 78 79 80

YEAR

FIGURE 5. AVERAGE ANNUAL CONTRACT PRICE FOR BITUMINOUSCONCRETE

13

(AFTER REFERENCE I)

Refining Asphalt

Atmospheric Distillation

Distillation at Reduced Pressure

Air Blowing

Solvent Refining

14

CRUDE OIL

1,450 Crude Oil Streams Available in Free World

975 Crude Oil Streams Presently Used in Free World

190 Crude Oil Streams Are Suitable for Manufacturin9 Asphalt

~ 40 Crude Oil Streams Used in Given Region of U.S.,

East Coast, West Coast, Gulf Coast, Etc.

15

PETROLEUM, ASPHALT AND TARS

A. PetroleumGasoline

Includes Naptha

Asphalt Base KeroseneI- - --[\Mixed Base Diesel- ---Paraffin Base Lube 011

Asphalt &Or \ill)(

1. Amount of constituents dependson crude.

2. Some crudes have very little«5%) asphalt or wax.

3. In general >25% asphalt in acrude will make it economicalto refine for asphalt.

4. As low as 10% in some cases.

OIL WELLn

PUMPINGSTATION

LIGHT DISTILLATE

TOWEROISTILLATION

RESIDU U,.:M:..._-,iIlIIIU*_,.OR J.......,....1ASPHAlT CEMENTS

REFINERY

FOR PROCESSINGINTO LIQUID

ASPHALTS

8 AIR

..srllL BLOWN

AIR ASPHALTI

!i GAS

ij

i PETROLEUM

-d- _.,

~ SAND AND WATER~-

Figure 1. Petroleum asphalt ftow chart lor aspball cement

17

ASPHALT

DIESELKEROSENE.

ETC.25%

KEROSENE

CRACKING

BOTTOM OFBARREL

20%

CRUDE OIL

GASOLINE

CHEMICALS10%

GASOLINE45-50

18

Texas State Department of Highways and Publ ic Transportation­Standard Specifications for Asphalt Cement (1972)

VISCOSITY GRADE

T~sl

VISl'O'ilty,

140 r "luke .....

SOC 1000 ,0001 112000

7U SII I i 111 !,----- +-_L_--l-_L_-'-_'--:-L--,----L-_~__

Sput Il'S! . " . _ keg,1I in' lor ;tll gradl':'\

19

Schematic drawing forillustrative purposes

Asphalts A & B are of thesame penetration grade.

275

Asphalts C & 0 are of thesame viscosity grade.

77 140Temperature, • F

o

Schematic drawing forillustrative purposes

>--·iiiot>.,>

27577 140Temperature, of

o

Na

Figure 4 - Variation In vlacoslly of two penetra·tlon graded asphalts at dlffe,.nt temperatures.

Figure 5 - Variation In viscosity of two viscositygraded asphalts at different temperatures.

Table Asphalt Producer Codes

Refi nery Code

*SDHPT **TTl

ProducerLocation/City

Sta te ofLocation

State Department of Highways and Public TransportationTransportation Institute from 1957 to May 1981. After May 1981 Texas Transportation Institute has

0 31 1023 154 15 86 67 58 219 12

10 171112 1113 22

N 14 2315 2416 1617 918192021222324252627282930

*Code used by Texas**Code used by Texas

used SDHPT codes

American Petrofina Co.APCOVickers Petroleum Corp.ChevronOdsoen Oil & Chem. Co.Diamond Shamrock O&G Co.Exxon Co.Gulf States Asph. Co.Gulf States Asph. Co.Gulf States Asph. Co.Kerr McGee Oil IndustriesOkmulgee Refining Co.Texaco Inc.Texas Emulsions Inc.Texas Emulsions Inc.Texas Fuel &Asph. Co.Trumbull Asph. Co. - HTrumbull Asph. - IRNuway EmulsionsNuway EmulsionsTexas EmulsionsNuway EmulsionsNuway EmulsionsNuway Emulsions, Inc.Macmillan Ring Free Oil Co. Inc.Texas Fuel &Asph. Co.Dorchester Refining Co. (formerly American Petrofina)Tosce CorporationOklahoma Refining Co. (formerly APCO)Pitucote Products Co.8itucote Products Co.

Mt. PleasantCyri 1ArdmoreE1 Paso8ig SpringSunrayBaytownBeaumontCorpus Chri s t iHoustonWynnewoodOkmulgeePort NechesAustinPort NechesLaCosteHoustonIrvingAdmoreArl i ngtonCorpus ChristiWoodwardPleasantonGarl andNorphletCorpus Chri s tiMt. PleasantEl doradoCyri 1El DoradoLake Charles

TXOKOKTXTXTXTXTXTXTXOKOKTXTXTXTXTXTXOKTXTXOKTXTXARTXTXAROKARLA

Table 5. Typical Properties of AC-I0 Asphalt Cements Used in Texas - Spring 1981

RefinerJ

Ori inal Aft r TestPenetratlOn V1SCOS ity IVl SCOS1ty Fl ash Poi nt Speclfic VlscoSlty Viscosi ty Penetration Retained Duc~i1i ty.Code nOF sec, 140°F 275°F COC, Gravi ty 1400 F Ratio nOF sec, Penetratior 77 F

dnm Stokes Stokes of Stokes dqm Percent cm

2 86 1116 3.46 600 0.995

4 91 895 2.32 600 1.029 2043 2.28 55 60 141

5 118 976 5.89 600 0.985 1524 1.36 84 7I 141

6 99 1145 2.60 600 1.020 2018 1. 76 63 64 141

8 91 986 2.40 600 1.021 1885 1.91 61 67 141

N 9 88 1102 2.60 600 1.023 2313 2.10 55 63 141N

10 100 1005 3.24 600 1.003 2153 2.14 62 62 141

11 128 951 3.30 600 0.993 1678 1.76 90 70 141

12 123 1004 3.35 590 1.030 2106 2.10 80 65 141

15 107 1011 3.10 595 1.025 2542 2.51 63 59 141

16 105 886 2.37 600 1.028

26 119 1007 3.40 600 1.023

Table 6. Typical Properties of AC-20 Asphalt Cements Used in Texas - Spring 1981

Refinery Ori inal After TestCode PenetratlOn IV1SCOSlty Vlscoslty flash POlnt '5pec1 flC IVlscos1ty V1SCOSity Penetration Retained uctil iW

77°F sec. 1400r 275°F COC Gravity HOOF Ratio 77°F sec. Penetration 770 rdlml Stokes Stokes of Stokes d0111 Percent cm

2 63 1910 4.11 600 1.009

3 75 1980 3.61 580 1.011 5108 2.58 50 67 141

4 60 1649 3.20 590 1.039 3771 2.29 38 63 141

5 80 1691 6.27 600 0.990 2842 1.68 58 73 141

6 67 1847 3.39 600 1.028 3683 1.99 44 66 141N

9 60 1983 3.55 600 1.026 3320 1.67 42 70 141w

10 57 2253 4.60 600 1.015 4878 2.17 40 70 141

12 83 1992 4.67 600 1.035 4302 2.16 52 63 141

15 80 2007 4.60 600 1.035 5253 2.62 49 61 141

16 . 63 1691 3.17 600 1.031 3829 2.26 38 60 141

17 58 2301 4.41 600 1.024 6104 2.65 35 60 141

24 95 2083 4.60 600 1.017 3757 1.80 69 73 141

26 87 1836 4.17 585 1.041

6 e4 6 e 103

2 4

VISCOSITY AT 60·C, POISES

2

"", , , I , ,

..

..'-

~:0013001

@

~NUMBERS INDICATE1» REFINERY CODE

~ • ~.

~"~

I20/1eoI ~~ -I~@t'm-@- •-8Sl1001 ~ ."t ~~~ ro ,

- eo/70I ~, ~ "- ............-~

- 40/!lOI ~.. ~

'-.

, I I ,IAC-IO' 'AC-20

I ,

AC-2.5 AC-5 AC-40

I I I I I I I I I 1 I I I I

10 210

20

1000800

600

E 400E

o-u 200•It)N

~z 1002 80~a: 60~ILlZ 40ILl0.

FIGURE 3.. RELATIONSHIP BETWEEN VISCOSITY AT eooc (140°F)AND PENETRATION AT 25·C (77°F) FOR ASPHALTSCEMENTS

(AFTER REFERENCE 14)

®AC- 2.5

200 300 400 500 600 700

VISCOSITY AT 135°C. CENTISTOKES

200 L....--L--.l._.&...--L...--L_"'----'---I._...I.--.L----J--J

100

6000

4000 IAC-40

enLLJ<,")

0 2000®~Cl.

~ 0® ®u°0(0

rAC-

IO~ 1000 ®~ @>- @:@~ 800en0u 600

AC- 5r",en®@ NUMBERS INDICATE> ®@ REFINERY CODE

400

FIGURE 4. RELATIONSHIP BETWEEN VISCOSITY AT60°C (140°F) AND 135°C (275°F) FORASPHALT CEMENTS

(AFTER REFERENCE 14)

25

N

'"

I

Asphalt B

RTFO*Aged

/

Original

Schematic drawing forillustrative purposes

Asphalt A

I>--:gorn:>

Schematic drawing forillustrative purposes

275o 77 140

Temperature, OF

Figure 7 - All asphalts do not harden the same.Compare with Figure 6.

275o 77 140

Temperature, *F

Figure 6 - After exposure to high temperature,asphalt becomes harder.

·ATFO - Roiling Thin Film Oven Test, used to simulateasphalt exposure in 8 pugmill.

Note - Figures 6 and 7 (as do 4 and 5) show general relation­ships of the temperature and consistency ofasphalts. These figures are not precise, but are'schematic drawings for illustrative purposes.

..tI)LUtI)-~

•LL.I::>0-tI)LUa::

l3u.....u..0

u0

~•

~>-...-tI)

0UtI)->

6

4

2

2

103

8

6

4

2

.

v/

V/ v

/

/ @J V7

i~@/l/7 • V~~

V ~'. y

V 17~

l)n. /

/ 14\ -~, 1/

R Jf.

i7 NUMBERS INDICATEREFINERY CODE

V/

2 2

- . VISCOSITY AT 60°C OF ORIGINAL ASPHALT, POISES

FIGURE 5. RELATIONSHIP BETWEEN VISCOSITY AT60°C (140°F) FOR ORIGINAL AND HEATEDASPHALT CEMENTS

27

40020040 60 8010020

~ 400 ....---....--.----....-.-.-......-----.------,

d•w

25 200 I--~,."....,:J=..".._..,...."..~=-I--+-+---+__+_,.......-l- NUMBERS INDICATEf3 REFINERY CODEQ:

~ 100I-----+----+--+-+--+--r-~ I'--.-----l

LL. 80 I----+----+--I--+~'----,.~+_-----ioU 601-----+----1---1--*o10N 401----+----+-"®;=7"~-+----+----I~

~i 201-:-.---+---7''--..,4-+---+-_+-+---+----1~ _1-11-1_W I Iz NEEDLE LOADING'!5s,IOOOW0-

1010

PENETRATION AT 25°C OF ORIGINAL ASPHALT, 0.1 mm

FIGURE 6. EFFECT OF TFOT HEATING ON PENETRATIONAT 25°C (nOF) FOR ASPHALT CEMENTS

(AFTER REFERENCE 14)

28

FIGURE 10. MINIMUM TEMPERATURE IN TEXASDURING THE PERIOD 1951 - 1980

-20

-5 o

5

-15

-10

, -15

5

-5

5

.,J.--f-+t--IO

'r-:~d---5

30

50

100

NUMBERS INDICATEREFINERY CODE

AC-5II

I

III

1000

20

Cf)W::£:

g 500Cf)

I-Z 300wu~ 200

LLo

lQ(\J

~>­I-Cf)

ouCf)

>

10 L-_---J'---J-_--1__---1.__-J-__--'- _

10 20 30 50 100 200 400

PENETRATION AT 77 0 F ,0.1 mm

FIGURE 7. ALLOWABLE MINIMUM TEMPERATURE FORAC- 5 ASPHALTS

(AFTER REFERENCE 16)

30

50

30

100

NUMBERS INDICATEREFINERY CODE

AC-IOIIIIII

1000

20

C/)LlJ:lI::

~ 500C/)

~

~ 300u

- 200u..°It)~

~>-~

C/)

ouC/)

>

40020010020 30 50

I 0 L--_--l'--~_ __'_____'___~____'_ _

10

PENETRATION AT 77°F, 0,1 mm

FIGURE 8. ALLOWABLE MINIMUM TEMPERATURE FORAC - 10 ASPHALTS

(AFTER REFERENCE 16)

31

lOll

109

10 7

106

105

'":.,;.:: 104'".....;;:.

103>-...5w .....

N CIl0 2uCIl

102.....>

5

2

10

5

2

LEGENDII , • - eapill a ry Tube Vi scometer

I' • - • - Sliding Plate MicroviscometerI 1-~ !,

A sec -1... - Schweyer Rheometer @ 0.01I 'N~, I

! '

sec- 1, i I iI~

, ~ - Schweyer Rheometer @ 1,I

, t'--- I! !"- • - Rheometri cs Spectrometer

, II,I --L .....

i ......1 II , , ! .....

....., ,

~ !i ,..........

"'-!

,~,

"-........

"'-........~

I,,-i', I

-40 -20 o 20 40 60 80 100 120 140 160 180 200 220 240 260 280

TEMPERATl~. DEGREES FARENHEIT

Figure E2. Viscosity as a Function of Temperature for Asphalt A2 (after TFOT).

ww

108

110

FIGURE II. MAXIMUM TEMPERATURE IN TEXASDURING THE PERIOD 1951 - 1980

112

108~ -106

110__ 108

21,--l---U..J---106

104

Table 13. General Recommendations for Asphalt Selection Based on Climatic Conditions.

Construction Season Spring Summer Fall WinterType of C1 imatic RegionAsphalt (Fig. 12) I II III I II III I II III I II III

of<Vl AC-5 X X X X X+' +'

~ e<tl".<=E AC-10 X X X X X X X X Xa..,Vl U..:

euo EA-HVRS X* X* X X* X* X* X* x* X* X.,... .....eVlo~.~ ::> EA-HVRS-90 X* X* X X* X* X X X X X X Xe E..: U.J

Vlue EA-CRS-2 X X.~ 0e·~

OVl.~~ EA-CRS-2h X X X X X X X X X X+'::><tlEU U.J

RC-2 X X X X X X X X

RC-250 X X X X X X X X

RC-3 X X X X X X X X

Vl RC-4 X X X X X.><:U<tl RC-5 X X X X X.0+'::>U MC-BOO X X X X X X X X

MC-3000 X X X X X X X X

Spring - March, April, May

Summer - June, July, August

Fall - September, October

Winter - November, December, January, February

*Do not use in high humidity areas**Use caution when using dusty rock.X-Indicates that this grade of asphalt should· not be used for defined applications.(After reference 33)

34

IA +5 TO+20 >35 HIGH

h¥,B + 5 TO +20 < 35 MODERATE I:--+---::--,--+--- ,-'-----1-=--=------i. IIA -10 TO +~_-L > 35 HIGHII II B - 10 TO + 5 i '--<---='35':"'--~----+-M-0-D-'-E:":R-'-A'-T-E---i1. - 26 TO - 10 --+,._--=-=-.. .L.!..!.!- - I < ...::3:..:5=--_--"....:M.:c.0,,-Dc_E=.;.:.RA-=T.:c.E:::...Ji

wV1

ZONE

MINIMUMTEMPERATURE

RANGE ,oFRAINFALL

INCHES PER YR. HUMI DITY

FIGURE 12. CLIMATE ZONESASSOCIATED WITHSELECTION OF ASPHALTTYPE FOR SEAL COATS

(AFTER REFERENCE 33)

Table 12. c.o.p.rison of Asphalt PI'Oduct Types U!led For Sur'~e Treo.. u.:-nts and S~al Co.ts.

As.pew It ')'pie

Aspn.1t Ce-enl

Aspha It Eauls ton(Anionic)

Aspha It E.. 1s ion(Cationic)

Cut-Bacf'. I\s~hf;lt

I. Few cure tt .. proble-s: ro.ad surface willusually accept traffic without rayeling whenroIling is c~leted.

I. Can be applied with little or no heat ondtstrtbutor.

Z. Water dflution can be usedexcept for rapid setting-.,hions.

I. Can be applied with little or no heaton distributor.

2. Good adhesion with all a99r~te types.

J. Good adhesion with moist aggregates.

4. Can be used in coot weather.

S. Resistant to wash-off If rainoccurs soon after ptace-ent.

I. Conventent to ~e: Unifo~ distribut10n

2. Requires lower spraying te.perature thanaspha J t cetilltnt.

J. Can be used in cool weather

4. Residue wtlt not be brittle incold ~lther.

Potenttal Probl~ft Areas~--~-~~----~-~-~--~~

I. High spraytng temperature required:a. ~y reduce durability of asphalt if overheated

b. Introduces operator ..afety and disco-fortproblees .

c. De-ands careful control to obtain unifonnasphalt distribution.

d. Is influenced by atMo'j,phertc and roadsurface temperatures.

2. Sensttlvity to aggregate surface eolsture.

3. Aggregate ~st be spread and rolled soon afterasphal t is distributed.

I. Separation of asphalt lind water on lorlljstorage or after freezing.

2. Asphalt stripping with high s11ica agqre9dtes

3. Emulsion ~y run off if road surface te-pera­lure is too high.

4. Cure t1me problellls: traffic control requireduntil cure is completed.

5. Will separate 1£ lIIhed with Cdtlonic f'lW.Ihions.

I. Separatlon of asphalt and water on long storageor after freeZing.

2. EMUlsion mdy run off if road surface t~np~ra­

ture 1S too high.

3. Water dilution may cause premature break

4. Cure time probleotS: trafflc control requireduntil cure 1S c~leted.

S. Will break jf e1xed with anion1c emulslons.

1. Cure time problems.

2. Cut-back sol'iellt createS air quality problems

J. Waste of energy in cut-back sol'ient.

4. Sol'ients have low flash and fire points thusworkman safety probl~.

5. Bleeding problems.

0.1 nin

~- -~ I- 2

106

43

----- I--- 2

t--"- ....

~--+--+---+----J--+--+--+--+~f---+--+--+~f--+--¥>i\:.......-JI"__.-+---+--+-+-I-----j-..j---+----+~l----I---+---I---

1- --+--+ ---+---+--+--+----+-if--~--'l.~-.:>..I""----- - ----I____. - --- --- - -- ---

l-_+__+- -t---+-+--+---

Range of Asphalt Properties After RTFOT for the Per-iod 1974-1979(West

-40

Figure 38.

-20 o 20 40 60 80 100 120 140 160 180 200 220 240

THIPERATUHE. °C

Coast Refinery)

2

106

43

2

5

1'\ \

I, 1\VISCOSITY, P

"~- ~~~ I-~ 1-l--~ I-- -- I---~ 1--

\.'\ I-- -

-- I-- .- - HlI'.P

- " --- I---~

----

"--

1'.."'- -I--

"~I~-

"'-l'-.._-I- ~-1-- --f--

~,,' "-~

~-- -

~- ---- ---1--- ~ . . - I--.~

""'"~

~- --- - --

"', l-

'\... "-~ I---- ~ ~ .- ~1-. -

"I""", "'-1"\ ""~l\..

PENETRATION, 0.1 11.11

12

5

102

5~

102

5

103

UJex>

Range of Asphalt Properties After RTFOT for the Period April

-40 -20

Figure 39.

o 20 40 60 80 100 120 140 160 1UO 200 220 ~40

THIPERATURE °C10, 1977 and June 1, 1977

0.1 IIIn

" \

PENETRATl ON,12

510

2

5 ~j~~j~il\'j'iijl::r==t=::r==t==t==t=l=+=+=+=+=++=t=~;;~~VISCOSITY, POISES

2 10610 '\ 1--- -- -- - -f--

2 ~jjiIRi1iH~lmB~--~E~}-E~~ 1051~3 ~ f- - - IHIII\

--t----t--t--j-----f'\.J---t--t--+--+-t--+--+-t--I--j---'IIl.---t---j-+--+-t--t---t'-----+--+-t---+--t--+--+--t--t--I---j­~

-----11----+-+---1 - -j-__+--l-+-+--+---+--"-'\..~I--+---+---JI---I--!--+-I---t--+-- -j--I--+--+- -+--.j--I--4

J---t--t--+--+--t---t---+-t--t--+-t-+-4!'..-"'-+,-t--t--t-+-.j--+-t--- --- -- --I--j------f-+---j-----4

106

43

- 2

- ---f-- f------- 1---1--+---1-+---I

-- ----

--------t----j----j--i---t-

"f---t--t---+---+---j--I--t----t-t--+--+---j--t-- t'''',,--f'-~,,+---+-t--+-f---t--I---j--I----t - -j---+-

'" "-f--- -- --

"" "I'nJ---t--t--t---t----J---I--+-----f-I---+-----,I--+---+-I---t---tI---t--+-"'.-+---j-'y--t--+--'-----l--'---->----'---'----1

-_:~ '~-- 34°F difference

I ~" I ",..~ 400F differenceI I I '" '" '"

Figure 37. Range of AC-20 Properties in a Northwest Texas Market Area

-40 -20 o 20 40 60 80 100 120 140 160 180 200 220 240

TEMPERATURE, DC

IMPROVEMENTS OF ASPHALT CONCRETES IN TEXAS

* Binders

* Mi xtures

* Specifications

40

POTENTIAL PAVEMENT MATERIALS

41

"NEW" PAVEMENT BINDERS

* Reduce dependence on petroleum products

* Large quantities of potential binders

would become available

* Need to improve quality of binders

* Relative rapid increase in cost

42

POTENTIAL "NEW" PAVEMENT BINDERS

* Plasticized Sulphur (Sulphlex)

* Cement Kiln Dust

* Lime Kiln Dust

* Fly Ash

* Altered Asphalts

43

SULPHUR BINDER SYSTEMS

* Sulphur Extended Asphalt (SEA)

* Sand-Asphalt-Sulphur (SAS)

* Sulphlex

44

PLASTICIZED SULPHUR

* Sulphur

* Plasticizers

60-80%

20-40%

TYPICAL PLASTICIZERS

* Cyclodiene

* Dipentene

* Vinyl Toluene

* Coal Tar

46

SULPHUR ASPHALT

* Recorded experiments in 1800's

* Further investi9ations in 1930's

* Most recent efforts since 1973

47

PROJECTS IN TEXAS

* U.S. 69 North of Lukfin - September, 1975

* U.S. 77 - Kenedy County - April, 1977

* MH 153 between Bryan and College Station ­

June, 1978

* Loop 495 in Nacogdoches - August, 1980

* IH 10, Pecos County

48

WOOD LIGNINS

* Kraft 1ignin

* Lignin sulphonate

49

FILLERS

* Lime

* Carbon Black

* Stone Dust

* Baghouse Fines

50

ALTERED ASPHALTS

* Sulphur Extended Asphalts

* Wood Li gni ns

* Foamed Asphalts

* Antioxidant Chemicals

* Antistrip Chemicals

* Temperature Susceptibility

* Fillers

51

ANTIOXIDANTS

* Oithiocarbamate salts

zinc, antimony, lead, copper

* Sodium Hydroxide

* Silicone oil

* SBR rubber

52

--,

---....:., --'"'1"''.;' ',_ .;••••,. '__ , ....., ..•~ :-:-'-'0· """ I' •••"'" .••• /~ ~ r.. '\. '_., ,., ..

":.~..::~~!~E~ ~l' , •~ I:.'\..... p':.'

''"'\ ~ •••0· ....... •

""'" ••.••:..'. ','0 • .;",""-.;: ,0 •• ' ........ 0# "

........ .,. I: • '0 ,'.":',,',:' .:'~~'..... (' ,',"' ....,.:

...

.........":' ..........'~':.::'''':\' ."" .': '.......' . '.

, .'" " ,.....~ . : ,.. .. .. ~ " " .........

, ".',.. ,,P,~I~~.: ~-;': ':~><. : ','J. "••• :'5 ~ :,'1 ,;... ! >"./'':>••• " .: • • • • ',:.:. I .. ', • ,', ...........",. • # • • ... • .,

_ ~ -....:-:.. '" • I, ,0 roo,,,,,,,,,,-- '

I,ooqoo

10,000o 10 100 140

53

TEMPERATURE SUSCEPTIBILITY

* Chemcrete - organic salt

* Asphadur - 3M

* Asphalt-Rubber

* Rubber-Asphalt

* Blending Asphalts

* Blending Asphalt with Recycling Agent

54

..

WATER SUSCEPTIBILITY

55

FIELD DISTRESS MOST COMMON

• HIGH MOISTURE SEASON

• HIGH TEMPERATURE

• HIGH TRAFFIC VOLUMES

• HEAVY TRAFFIC

• POOR DRAINAGE

• PERMEABLE SURFACE

56

SURFACE COURSE - ASPHALT CONCRETE

LEVELING COURSE - ASPHALT CONCRETE

AGGREGATE BASE

57

\ ASPHALT CONCRETE OVERLAY)

ASPHALT CONCRETE OVERLAY )

(

PORTLAND W1ENT CONCRETE

58

)

f

ASPHALT CONCRETE

BLACK BASE

59

) ASPHALT CONCRETE OVERLAY

w(

PORTLAND CEMENT CONCRETE

60

ANTISTRIP CHEMICALS

* Lime

* Lime slurry

* Chemical Additives to Asphalts

* Chemical Additives to Aggregates

61

RECOGNITION OF WATER SUSCEPTIBILITY PROBLEMS

• FIELO OISTRESS

Excess Asphalt on Surface (Flushing)

Rutting in Wheel Paths

Instabil ity

• FIELD TESTS

Unable to Obtain Core

Brown Color Mixture

Mixture Can be Removed With Shovel Sometimes by Hand

Asphalt Will Stick to Hands

• LABORATORY TESTS

Loss of Strength After Exposure to Water

Gain of Strength Upon Drying

62

RECOGNITION IN LABORATORY

• VISUAL

• STRENGTH REOUCTION

* Tensile Strength

* Resilient Modulus

* Hveem Stability

63

WATER SUSCEPTIBILITY TESTS AT TTl

• MODIFIED LOTTMAN PROCEDURE

Vacuum Saturation - 30 Min.

18 Freeze- Thaw Cycles (4 hrs. oaF - 4 hrs. 120°F)

• MODIFIED CHEVRON

Vacuum Saturation - 120 Min.

7-Day Soak

64

POSSIBLE SOLUTIONS

• AFTER PROBLEM OCCURS IN PAVEMENT

• ALTER DESIGN

• RECOGNITION IN LABORATORY

65

FIELD DISTRESS

• SEAL SURFACE

Fog Seal

Slurry Seal

Chip Seal

Asphalt Concrete

Interlayer + Asphalt Concrete

• SEAL UNDERSI DE

• REMOVE AND REPLACE

66

ALTER DESIGN DF MIXTURE

• ASPHALT

Increa se Content

Alter Asphalt (Anti-Strip Agents)

Change Asphalt

• AGGREGATE

Grada ti on

Surface Chemistry (Lime)

Change Aggregate

• MIXTURE

Air Void Content

67

ANTI-STRIP AGENTS

• DRY LIME (1.5%)

• LIME SLURRY (1.5%)

• COMMERCIALLY AVAILABLE ASPHALT ADDITIVES

A = Pave Bond Special (Cincinnati Mi1acron)

B = M-200 (Texas Emulsion)

C =82-S (Armak)

68

DESIGN OF PAVEMENT

• SEAL MIXTURE FROM WATER

Chip Seal

Fabric Interlayer

Asphalt-Rubber Interlayer

• ALLOW FOR STRENGTH REDUCTION

69

MIXTURE DESIGN

OVERALL OBJECTIVE OF MIXTURE DESIGN

To design a mixture which will perform satisfactorily in a pavement

STRESSES NEW PAVEMENTS

- Load Stresses

- Thermal Stresses

- Contraction Stresses

FACTORS AFFECTING STRESSES ARE

1. Stiffness of each layer

2. Thickness of each layer

3. Applied wheel load

70

4. Tire pressure

5. Coefficient of thermal expansion

6. Temperature

7. Pavement age

OTHER STRESS CONSIDERATIONS

Residual stresses

Load-induced stresses not directly under the wheel

SPECIFIC OBJECTIVES OF MIXTURE DESIGN

To determine an economical blend and gradation of aggregates and asphalt;

a. sufficient asphalt to ensure durability

b. sufficient mix stability strength, fatigue, etc.

c. sufficient voids for additional compaction

yet low enough to keep out air and water

d. sufficient workability for placement

71

PAVEMENT DISTRESSES

Cracking

Thermal

Shrinkage

Fatigue

Permanent Deformation

Rutting

Shoving

Disintegration

TEXAS DISTRESS PROBLEMS

Durability

Stripping

Softening

Shoving

Fatigue Cracking

DESIRABLE MIXTURE PROPERTIES

Strength

Stability

Flexibili ty

Stiffness

Fatigue Resistance

Durability

Skid Resistance

Workability

72

STRENGTH

Strength is primarily concerned with the ability of the mixture to withstand

loads (stresses) and deformations (strains) without cracking. Primary concern

should be with tensile stresses and strains since traffic and environment sub­

ject the pavement and mixture to tensile conditions.

Tensile Tests

- Cohesiometer

- Flexural (beams)

- Indirect tensile

STABILITY

Stability of an asphalt pavement is its ability to resist shoving and

rutting under traffic loads. A stable pavement maintains its shape and smooth­

ness under repeated loading; an unstable pavement develops ruts, washboard

ripples or corrugations, shoves, etc.

Because establishing stability specifications for a pavement depends on

the traffic expected to use the pavement, stability requirements can be estab­

lished only after a thorough traffic analysis. Stability specifications should

be high enough to handle traffic adequately, but not higher than required. Too

high a stability value may produce a pavement that is too stiff and therefore

less durable and less resistant to fatigue and thermal cracking than desired.

73

FLEXIBILITY

Flexibility is the ability of an asphalt mixture to adjust to gradual

settlements and movements and to withstand load or environmentally-imposed

deformations without cracking. Sometimes the need for flexibility conflicts

with stability requirements, so that trade-offs have to be made.

Tests

No good tests to measure flexibility

STIFFNESS

Stiffness refers to the relationship between load (stress) and deformation

(strain). A material with a high stiffness will not deform as much under load

as a less stiff material. This property is closely related to stability and

flexibility and is often considered to be the same as modulus of elasticity.

Stiffness Tests

Compression

Beams

Indirect Tension

E = applied load (stress)deformation (strain)

applied load (stress)S = ""7"-::----":<_'-"-="7"':='::='-+::":::';'=:='---:-­deformation (strain) at some time

74

FATIGUE RESISTANCE

Fatigue resistance is the mixture's ability to resist repeated bending

under wheel loads (traffic). As the percentage of air voids in the pavement

increases, by either design or lack of compaction, pavement fatigue life (the

length of time during which an in-service pavement is adequately fatigue-resis­

tant) is drastically shortened. Likewise, a pavement containing asphalt that

has aged and hardened significantly has reduced resistance to fatigue.

The thickness and strength characteristics of the pavement and the

supporting power of the subgrade also have a great deal to do with determining

pavement life and preventing load-associated cracking. Thick, well-supported

pavements do not bend as much under loading as thin or poorly-supported pave­

ments do. Therefore, they have longer fatigue lives.

Fatigue Tests

Beams (bending)

Indirect tensile

DURABILITY

The durability of an asphalt pavement is its ability to resist ,factors

such as changes in the asphalt (polymerization and oxidation), disintegration

of the aggregate, and stripping of the asphalt films from the aggregate. These

factors can be the result of weather, traffic, or a combination of the two.

Durability Tests

No good tests for mixtures except for moisture susceptibility

75

SKID RESISTANCE

Skid resistance is the ability of an asphalt surface mixture to minimize

skidding or slipping of vehicle tires, particularly when wet. For good skid

resistance, tire tread must be able to maintain contact with the aggregate

particles. Mixtures that tend to rut and bleed present serious skid resistance

problems.

WORKABILITY

Workability describes the ease with which a paving mixture can be placed

and compacted. Mixtures with good workability are easy to place and compact;

those with poor workability are difficult to place and compact. Workability

can often be improved by changing mix design parameters such as aggregate type

or gradation. Mix workability is related to pavement stability and density;

however, there are no set test procedures whereby problems with workability can

be positively identified in the laboratory.

76

FACTORS IN DESIGN

' ...

AGGREGATE

REPRESENTATIONOF VOLUMES

IN A COMPACTEDASPHALT SPECIMEN

AIR VOIDS

AGGREGATE

MIX SPECIMENWITH

ASPHALT REMOVED

AIRVOIDS

VMAASPHALT

~~~~~~: AGGREGATE

COMPACTED ASPHALTMIX SPECIMEN

NOTE: The volume of absorbed asphalt is not shown.

MINIMUM PERCENT VOIDS IN MINERAL AGGREGATE (VMA)

U.S.A. StandardSieve Designation>

Nominal MaximumParticle Size t

in.·

Minimum Voids inMineral Aggregate,

Percent

1.18 mm (No. 16)2.36 mm (No.8)4.75 mm (No.4)9.5 mm ("Ia in.)

12.5 mm (1/2 in.)19.0 mm ("14 in.)25.0 mm (1 in.)37.5 mm (1 1/2 in.)50 mm (2 in.)63 mm (2 1'/2 in.)

0.04690.0930.1870.3750.5000.7501.01.52.02.5

23.52118161514131211.511

*Standard Specification for Wire Cloth Sieves for Testing Purposes, AASHTO Designation M 92.tFor processed aggregate, the nominal maximum particle size is the largest sieve size listed in the applicable

specification upon which any material is permitted to be retained.

77

Asphalt

- amount

- viscosity

- temperaturesusceptibility

Aggregate

- amount

- type

- natural vs. crushed

- surface texture

- gradation

Air Voids

- 3-5% for surface courses

- 3-8% for base courses

VMA

Minimum 11 - 23%

Depends on maximum size

FIELD STABILITY

Dependent on aggregate interlock and cohesion due to binder.

78

Angular AggregateCompacted Mass

Angular AggregateWith Asphalt

Rounded AggregateCompacted Mass

Angular AggregateWith Excess Asphalt

79

>t-::;iiict­III:><i2ww>:z:

ASPHALT CONTENT

IAT MAXIMUMSTABILITY

------'::-::-lII"-!'oo..

•ASPHALT CONTENT

OF THE MIX

CAUSES AND EFFECTS OF PAVEMENT INSTABILITY

LOW STABILITY

Causes

Excess asphalt in mix

Excess medium size sand in mixture

Rounded aggregate, littleor no crushed surfaces

80

Effects

Washboarding, rutting, andflushing or bleeding

Tenderness during rolling and forperiod after construction, diffi­culty in compacting

Rutting and channeling

•

HVEEM DESIGN

Determines asphalt content at 3% air voids

Measures stability at 97% of theoretical density

Hveem stability test measures aggregate interlock

INDIRECT TENSILE TEST

Measures cohesion and tensile strength

COHESION

Depends on viscosity (stiffness) and mineral filler content

81

FILLERS IMPROVE

Cohesion through increased apparent viscosity and binder stiffness and

waterproofing

Many Texas mixture designs have a deficit of minus 8200 material (filler)

RECOMMENDED MAXIIIUM FILLER CONTENT

W • weight of asphalta

Wf

• weight of filler

Gf = specific gravity of filler

FILLERS

Lime

Carbon Black

Stone Dust

Baghouse Fines

82

Many Texas mixture designs have a deficit of material between the minus

#40 and plus #ijO material (a hump in the gradation curve).

Specifications for aggregate gradations need to be evaluated

Nos. 40 to 80 sieves

% fines

Distribution of aggregate sizes

83

100

Grading+-1--

Limits

;

/_~~~-.,/ / Harsh Mixture:

/ Inclined toI segregate

II

Costly Mixture:Aggregate easto finish

Critical Mixture:Unstable withexcess asphalt ;water ",,

,--,,' ---- - Porous Mixture: Low~ ----_.- ",- Tensile strength. Use higher;fJfJ viscosity asphalt,....__...

o .1:::::1=----L.5----.J1~--::-5~I0~--=--~5~0~100

Aggregate Size J % of Max. Size

-c-

0'

.: 80U)U)

ca..C 60Q)(.)~

Q)

a..Q) 40>.-

Percent Mechanical Analysis Percent

Retained #200 #SO #40 #10 #'4 3/S" 7/S'I Passing

10I I l 90Fuller Curve:

//20 P=IOO(~)O.45 SO.:JWhere P = Percent Passing a

30 Particular Sieve ....1.' 70.... 'tS = Size of Opening for

40 .llt 60a Particular Sieve :"/." 'M= Maximum Size of ../f/

50 Aggregate in microns /:.: :./ 50r

60 Design 5 -k /~; 40

70 ~~~Design2

?\O~ ...

SO Design I~ .~ ·..····"-Fuller20?' ....

1/.....

90 .... 10

?100~: ...

0Fine Sand Coarse Coarse

-Soil Binder- Sand Aggregate

Example of typical gradation curve

85

Asphalt content tolerance of ± 0.5% needs to be evaluated

Increase required Hveem stability value to 35 or 40

Asphalt viscosity should be evaluated relative to its effect on stability and

strength

Effect of plant temperature needs to be evaluated

Temperatures

Laboratory

Mixing

Compaction

Field

275°F

250°F

Varies widely and typically does not correspond to

lab values

86

>.-10oU10

>

o 77 140Temperature, of

275

>.-10oU10

>

o 77 140Temperature, °F

275

00....

........ .... -- ....Original 7 ................ - .... -.

10oU10

>

>.-10oU10

>.->

o 77 140Temperature, of

275 o 77 140Temperature, OF

275

METHODS FOR INCREASING STABILITY

Optimum asphalt content

Dense, well-graded aggregate

Angular particles

Rough surface texture

Mineral filler

High viscosity asphalts

Oxidized asphalts

STRENGTH

Tensile Tests

Cohesiometer

Flexural

Indirect tensile

88

TENSILE TEST LOADING ARRANGEMENT

Indirect tensile test can be conducted using the large gyratory press

References:

Anagnos, J. N., and T. W. Kennedy, "Practical Method of Conducting theIndirect Tensile Test," Research Report 98-10, Center for HighwayResearch, The University of Texas at Austin, Austin, Texas, August 1972.

Kennedy, T. W., F. L. Roberts, and J. N. Anagnos, l~ethod for Conducting theStatic and Repeated-Load Indirect Tensile Test," Research Report 183-14,Center for Transportation Research, The University of Texas at Austin,Austin, Texas (in progress).

89

400

350

300

250on......

(/)

s:a. 200c..-..onc~ 150

100

••

50

24020080 120 160Asphalt Penetration 01 77°F. 100Q. 5 sec

40

0L.. -I- ---l .L- -L --.JL-__--J

o

90

4000

3500

Eagle LakeGravel

AVRDesign Optimum, 550

500

3000

'"~ 2500..c'"'""c:(j)

t 2000til

(j).....•.-<'fJc:~ 1500

IIIIII

Line of IOptimums f

( I.---------.:

IIIIII

450

400

350

300

250

200

(j).....•.-<'fJc:(j)

E-<

1000

5001000 F

0-

IIIIII

0;----0- _-0

150

100

50

3.5oL-L-------L.-----"::-----;~~O

4.0 4.5 5.0

Asphalt Content, % by Weight

91

Int......diat.Made

Controlled Strain

FATIGUE TESTS

Flexural (bending)

Indirect Tensile

Fatigue Loadings

Controlled (constant) stress or load

Controlled (constant) strain or deformation

Fatigue Life (log scale)

Controlled stress loading simulates stresses in thick asphalt concrete

pavements

Controlled strain loading simulates stresses in thin asphalt concrete

pavements

92

FATIGUE RESISTANCE

% Asphalt

% Air Voids

Gradation

Stiffness

93

AVR Design Optimum"

I/~~"

SO°F

Tens iie Stress 14.5 psi

7S0F

8.S

100°F

8.07.S7.06.S

103 '-- '-- ..l.-__'--..L-- ..L-- ...1.-_

6.0

Asphalt Content, % by Weight

94

FACTORS AFFECTING THE STIFFNESS AND FATIGUE BEHAVIOROF ASPHALT CONCRETE MIXTURES

Effect of Chan~e in Factor0""

Factor Change in Factor an Fatigue Life an Fatigue Litan in Controlled- in Controlled-

Stiffness Stress Mode of Strain Mode ofTest Test

e

AsphaltDecreaae Increase Increase Decreasepenetratioa

Aaphalt Increase Increases a h

content Increase Increase

Aggregate Increase roughnesa Increaae Increase Decreaaetype and angularity

Aggregate Open to denaeIncrease Increase Decrease d

gradation gradation

Air void Deereaae Increase Increase Increase dcontent

Temperature Deereaae Increaae e Increas. Decrease

a Reachea optimulll at level above that reqUired by stability considerations.b No aignificant amount of data; conflicting conditions of increase instiffneas and reduction of strain in asphalt make this speculative.

cApproaehea upper lmit at temperature below freezing.dNo aignifieant amount of deta.

95

Causes

Low asphalt content

High design voids

Lack of compaction

POOR FATIGUE RESISTANCE

Effects

Fatigue cracking

Early aging of asphalt followedby fatigue cracking

Early aging of asphalt followedby fatigue cracking

Inadequate pavement thickness Excessive bending followedby fatigue cracking

DURABILITY

Problems

Asphalt polymerization and oxidation

Aggregate disintegration

Stripping of asphalt from aggregate

POOR DURABILITY

Causes

Low asphalt content

High void conten t through designor lack of compaction

Water susceptible (hydrophillic)aggregate in mixtures

Effects

Dryness or ravelling

Early hardening of asphalt followedby cracking or disintegration

Films of asphalt strip from aggregateleaving an abraded, ravelled, ormushy pavement

96

STRIPPINC

Loss of adhesion between tbe asphalt cement and the aggregate surface is

primarily due to the action of water.

Other contributing factors are aggregate surface coatings, smooth aggregate

surface texture, and raveling.

RAVEL INC

Progressive disintegration of an asphalt mixture layer from the surface

downward by disiodgement of aggregate particles caused insufficient asphalt,

hardening of asphalt, wet or dirty aggregate, smooth aggregate texture, and/or

surface stripping.

METHODS FORREDUCING MOISTURE DAMAGE

Eliminate moisture

compaction

sealing

drainage

Eliminate use of moisturesusceptibility aggregates

Treat aggregates

liquid antis trippingagents

lime

97

MOISTURE SUSCEPTIBILITY TESTS

Static Indirect Tensile Test

Repeated-I,oad Indirect 'fensile 'fest

Texas Freeze-'J113w Pedes tal Tes t

llo il in/\ Test

WET-DRY TESTS

INDIRECT TENSILE TEST ON WET AND DRY SPECIMENS

In the indirect tensile test a cylindrical specimen is subjected to

compressive loads distributed along two opposite generators that create a

relatively uniform tensile stress perpendicular to and along the diametrical

plane, which contains the applied load, that leads to a splitting failure.

Estimates of the tensile strength, modulus of elasticity, and Poisson's ratio

can be calculated from the applied load and corresponding vertical and hori­

zontal deformations.

All speci.mens are tested in indirect tension, and the moisture suscepti­

bility is determined by the ratio of tensile strength in a wet condition to

that in a dry condition. Wet specimens are prepared by subjecting 4-in.­

diameter specimens to various amounts of mercury pressure in water, releasing

the vacuum, and the water forcing by atmospheric pressure into the voids

available in the mixtures. After vacuum saturation, some specimens were

placed in a plastic bag along with a small amount of water, and then subjected

to various thermal cycles. All wet specimens are submerged in a pretest water

bath before testing.

98

•

•

•

•

•

•

•

•

•

•

o

o

o

26F/TH

o[]

~~ 10 ~T"ho;:' :VS~~ t t:J

,~~ 0.5r t:J. •co:: 0 Strippino Mixtures~ • Nonstrippino Mixtures

o L-..-'----'---~'----'----J.-I_L-----L'-----',-----',-----',--

10 Technique 26 VS + Soak (7 days)

l~ .f t:J

en ~ t:J

.!!?~ 0.5L' 0'en cco::~

o _.l-_.l-__L._+-~'--- LI_----'_--l_---I__= 0 TechniqueCll I.Co::~eniiit-

o~.;: 05.. 0::> •co::t!

••••

[][]oo

Technique 26 TC

0L--L_.L---L_...L.-.--j._J-~_---L_L--L_

= 1.0CllCo::~eniiit-.!!? _~ 0.5,--",0::>co::~

o ..l.-.L'_-+_----L__--'-_----'_----'_----'_

9 II 12 13 5 12 14 19Waco Lufkin HOUlton Yoakum Lubbock HOullon Au,lln Allanta

( HarriS Co) (Gall/eston Col

Asphaltic Concrete Mixture Source

99

Generally recommended cutoff value for TSR is between 0.70 and 0.75.

Mixtures with TSR values below this value are considered to be stripping-prone.

TEXAS FREEZE-l~W PEDESTAL TEST

This test determines the number of freeze-thaw cycles required to induce

cracking on the surface of a specimen. This test procedure involves subjecting

miniature asphalt-aggregate briquets to repeated freeze-thaw cycles in water.

The briquets are highly permeable to allow easy penetration of water and are

designed to minimize mechanical interlocking of the aggregate particles by

using a uniform aggregate size. Thus, the briquet properties are largely

determined by the asphalt-aggregate bond. The moisture susceptibility of an

asphalt concrete mixture is evaluated by determining the freeze-thaw cycles

required to crack a briquet seated on a beveled pedestal.

Research Report 253-3, "Texas Freeze-Thaw Pedestal Test for Evaluating

the Moisture Susceptibility of Asphalt Mixtures"

100

1'"Show Stripping in Field

"I~Nonstripping in Field

--\>25 8 8 8 8

01C

-'" 2000...(.)

0 15-,... C/)0 Q),... -

0>-(.) 10

0~

00.c~

I 5 0Q)NQ)

0Q)...LL

0Waco Lufkin Houston Yoakum Lubbock Houston Austin Atlanta

(Harris Co.) (Galveston Co,)Material by District

TEXAS BOILING TEST

In this test a visual observation is made of the extent of stripping of

the asphalt from aggregate surfaces after the mixture has been subjected to

the action of water at elevated temperatures for a specified time. Many

agencies have used different versions of the boiling test to evaluate the

potential stripping of asphalt mixtures. To perform this test the cool, loose

asphalt mixture, either plant or laboratory mixed, is boiled in distilled

water for 10 minutes. After boiling the water is drained, the contents

emptied on paper, and the extent of stripping is visually rated. The method

can also be used to evaluate the effectiveness of candidate antis tripping

additives in asphalt-aggregate mixtures.

102

/.., Show Stripping in Field ---+f---- Nonstripping in Field ----t-i~

100

Waco

OL...---'-'--_--'--'-_---''--'-__..l-J'-----_---''''"'--_---'"'''--__-''''''--_--''-'"--Lufkin Houlton Yoakum Lubbock Houston Austin Atlanta

( Harris Co) (Golveslon Co)

ClC

o 80III.....--<l:

"'C 60..co-£- 40o~

0­III<l:-o 20­c..u...:

Materials by District

ANTISTRIPPING AGENTS SUMMARY

I. All antis tripping agents should be tested with the proposed asphalt and

aggregate

o Freeze-Thaw Pedestal

o Texas Boiling

o Wet-Dry Indirect Tensile

2. Liquid antistripping agents are relatively ineffective but work with some

aggregate-asphalt combinations

3. Lime is generally effective as an antis tripping agent

l~

GENERAL OBSERVATIONS ON LIME

Reaction involves asphalt and not aggregate.

Carbonation makes the lime ineffective, thus prolonged exposure of the lime or

the treated aggregate is detrimental.

Slurry holds the lime on the aggregate, thus allowing asphalt at the interface

to be treated.

METHODS OF APPLYING LIME

1. Lime slurry is best method of application (especially for drum mixers).

2. Dry lime is effective if it can be kept on the aggregate surface.

3. Mixing dry lime directly in asphalt cement not recommended.

105

SKID RESISTANCE

Skid resistance is the ability of an asphalt surface mixture to minimize

skidding or slipping of vehicle tires, particularly when wet. For good skid

resistance, tire tread must be able to maintain contact with the aggregate

particles. Mixtures that tend to rut and bleed present serious skid resis­

tance problems.

106

WORKABILITY

Workability describes the ease with which a paving mixture can be placed

and compacted. Mixtures with good workability are easy to place and compact;

those with poor workability are difficult to place and compact. Workability

can often be improved by changing mix design parameters such as aggregate type

or gradation. Mix workability is related to pavement stability and density;

however, there are no set test procedures whereby problems with workability

can be positively identified in the laboratory.

107

WORKABILITI

Aggregate Factors

- gradation

- surface texture

- shape

- maximum size

Asphalt Factors

- laydown and compactiontemperature

- viscosity

- % asphalt

108

PLANTS

109

TYPES OF PLANTS

* Batch

* Continuous

* Drum

110

1-103 The same sequence is illustrated here; the different placements of the

parts will broaden your overview of the plant's structure.

ASPHALT

A. Proportioned amounts of and aggregates are

fed into the dryer.B. The aggregates are shown stored in hot bi ns after screening.

(number)C. Measured amounts from each hot bin are mixed with and

-----------------------------------------------------------------------------

111

BASIC ELEMENTS OF BATCH PLANT

* Aggregate Stockpiling

* Asphalt Storage

* Cold Aggregate Bins

* Cold Aggregate Feeders

* Dryer

* Hot Screens

* Hot Bins

* Batching

* Mi xi ng Unit

* Hot Storage

112

1-104 Now you can follow the same basic steps in a sketch of a hot mix plant.

~CREENIHG

UNIT

--------------------------------------------------------------------------------

113

--------------------------------- -----------------------------------------

ASPHALT BATCH MIX PLANT

C__ ol __ - __..

-.,......-.. -..- ..._,...1"",_.,... __ .-...... ---._ ....-....

!... _ ..- '-0 •.•• _ _'b·••• · _ ....'._ ..._ -,. ~ •. ~ .

COlO AGGIEGAn SlO....GEANO fflO-.. _-- ....-""'_ .. _~ _-._....._...:.~_ -

,

/.........,.~._----_10-

(;n...... _ .. .,... ~__~.......

....... -......

• _M""" ,..........- _ -..'.-

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c.......... t _, ,_......._ , -

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-.. ~...._~- .......-...-- -_.... ---_.-- .... ,---

.......--- .. ~_ ..--_...... -,.....

...._-- ...,... - ............ - -._.

••_.........._0 ..........., A._--

"-" "'- -'", -~.",..._ __ .....

Fi9ure 44. Asphalt batch ~ix rlant (52).

Figure 6. Three-bin cold feeder and bell

J 16

I--"''''''''............._ i, "'7•••••,;;..I"'{f"'; _.

Figurl..' II. J)r~ cr lIsed in a ccntral mixing plant(Cou. tcsy Rorber _Cree ne Co. )

I )7

ex>

Fi~urc 12. Cutaway ,'iew sho",'in~ details of Itow ofmaterial through screens and bins

(Courtely Iowa Manufacturing Company)

;' ,i r. ,

:--__t,./~~~~

--4._

Se regalion ofFil!ure .6. . t~e hot hinsmaterials m

119

••,•

~.. "

'. \. '•

Figure I~.

120

0t:PFigure 15. Pugmill mixer for a h3h:h plant

(Courtesy Iowa Mon"fo:lurll"lg Com pony)

121

Figure 2. O.erfilled pugmill

Fi~urc 3. llndcrfillcd pugmill

---/~~'~~--~:~--~~~---

'" " ", ....'" ,/ "-/ 1\ '\

I I \ \I I \ \

I \I I1 I\ I

\ I\1

122

TLIVE

ZONEFigure 4. Pugmill "Ii.e zone"

BASIC ELEMENTS OF DRUM MIXER PLANT

* Aggregate Stockpiling

* Asphalt Storage

* Cold Aggregate Bins

* Cold Aggregate Feeders

* Drum Dryer and Mixer

* Hot Storage

123

~==r./ Ii, I: MIX

DRYER.D".UM MIXER qHOT-MIX CONVEYOR $ I ; SUHGE

liE/~- --_.__ _ g - [. SILO

,y"/ -----...,- ~ . •

. . ~ i - .ff t--;/'. ' i,~~~ I gfr: ~I

_ ASPHAL T I i;AS!,HALTSTORAGETANK~~£, ~_.1L

AUTOMATICWEIGHING SYSTEM

COLD FEED CONVEYOR

COLD FEED BINS

Wr'J.."Q~d"N~

Figure 1II·26-Asphalt dryer drum mix plant

Fij.turc 5, f)i~lgram of continuous-t)'PC process(Covrteiy 8orbe r-Grl:cnl: Co.)

125

ASPHALT CONTINUOUS MIX PLANT

.. ''-._-...-,-­.... ..- ... -......_..._-_._ ..... - .........

COLO Aoo.GA" STOUoGI....---- ...._-_...~---_ ..­-_ ..--~~-

---------

e-..... _-------......._----..... _._ ... ..--

-----_...-'::::.:::."'-~ .. -----.-~_.. _... __ .- ~-::..=- .. _....

~---.,-­---..-_ ....... ­~

Figure 43. Asphalt continuous mix plant (52).

OPERATING AND INSPECTION OF ASPHALT PLANTS

* Materials Handling and Storage

* Cold Aggregate Feeding

* Drying and Heating

* Screening and Grading

* Temperatures

* Balanced Flow of Materials

127

RECOMMENDED ASPHALT VISCOSITIES FOR MIXING

Type ofViscosity

Mill. Kinemalic, u Soybolt.Furol .•ec,

dense-graded 150-300 75·150

open·graded 300+ 150+

128

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" -<::~{:}:),. "~'\' Alternate__ -'-" Posihon

/' -- ""'" of Handle

Figure 7. Aspbalt plantaggregate sampling device

Figure 8. Correct use 01sampling device

TABLE 1IN

POSSIBLE CAUSES OF MIX DEFICIENCIESHOT PLANT-MIX PAVING MIXTURES

w

'"

I. PLANT INSPECTOR'S CHECK LIST. for the convenienceof the Engineer and the Inspector. some of the more im­portant details of inspection in production of the hotmixasphaltic concrete are listed below:

I. Determine that the testing tools and equipment areon hand and in good condition. Make sure youunderstand all the tests.

2. Inspect <lll components of the mixing plant. andmake sure that all deficiencies are corrected be­fore mixing is begun.

3. Check all scales for accuracy periodically. anddetermine correct adjustment to zero daily.

-4. See that the stockpiled aggregates are kept sep­arate. and thotno intermingling occurs at the coldfeeders.

5. Check the temperature of the heated aggregatefrequently.

6. Watch for evidence of incomplete combustion ofthe burner fuel, as evidenced by dark smoke fromthe plant exhaust and coating on the aggregate.

7. Check the temperature of the asphalt frequently.

8. Establish the scale settings for the batch weights.and station the Weight Inspector at or near thebatching scales so that he can observe the weigh­ing of the aggregates and asphalt.

9. Daily check the screens. bins. and overflowchutes for proper operation.

10. Check an occasional batch to see that it 1s mixedthe required length of time.

11. Make frequent visual inspections of the mix leav­Ing the plant for evidence of non-uniformity orincomplete mixing.

12. Check the temperature of the mix frequently.

13. Inspect the truck beds before loading; see thatthe t:ru.ck beds are free of congealed chunks ofmix and excess diesel oil.

14. Check occasionalIy with the Road Inspector con­cerning workability and uniformity of the mix atthe paving machine.

15. Take samples of the mixture for extraction testand for molding the Hvp('m stability specimens.Sample the aggregates from ,he hot bins and per­form the combined sieve analysiS.

16. Maintain an accurate and complete record of allthe test results. the number of batches mixed.the quantity of the asphalt used, and other per­tinent data.

COMPACTION

DENSITY the unit weight of the asphalt mixture.

Density increases with

Greater compactive effort

Higher asphalt content

Increased mineral filler content

Higher aggregate specific gravity

COMPACTION is the process of densification of a mixture by

mechanical means, i.e., the asphalt and aggregate are

compressed into a smaller volume.

PURPOSE OF COMPACTION

Improve the engineering properties and performance characteris­

tics of the asphalt mixture

• Increases stability

• Reduces air voids

• Increases density

• Smooths surface

133

METHODS OF ACHIEVING COMPACTION

Construction Rolling

Traffic

Construction Rolling

• Compaction by static weight

• Compaction by kneading action

• Compaction by vibrating rollers

FACTORS AFFECTING COMPACTION

Aggregate Factors

Surface Texture

Soundness

Porosity (absorptive aggregates)

Gradation·

Asphalt Factors

Viscosity (Grade)

Temperature at compaction

Amount

134

IMPORTANT EQUIPMENT FACTORS

Compaction Pressure

Roller Speed

Vibration Frequency

Vibration Amplitude

Amplitude is based on lift thickness and support conditions

• Use low amplitude on thin lifts

• Use high amplitude on thick lifts

Frequency is the number of impacts per minute

2000 - 3000 vibrations per minute typical

135

AMPLITUDE is the peak to peak vertical movement of

the drum.

SUGGESTED RECOMMENDATIONS:

Thin Lifts ( t < I in.) -

use low amplitude

Medium Lifts ( I in. < t < 2 in.) ­

use medium amplitude

Thick Lifts ( t > 2 in.) -

use high amplitude

Roller speed is used to define impact spacing.

Impact spacing is the distance traveled between

impacts.

lllliitillImph 2mph

111111111[1'3mph

Impact SpacingRoller Speed (ft./min.)

Vibrating Frequency (rev./min.)

136

•

Normal Working Range-,Present Equipment Capa bility. I•

---Minimum Recom­mendation impactsper 1t

N.'Y. 0.0:r.

NAPATRB-Thin Lifts

TAl

-

25

.....0 2001.L

a::W 15a..

.... CJ)w

10" .....U«a..

5~

O~_--L__--L-_--'----_--L__-..L...._--'-----""""""-_-..L...._-

o 500 1000 1500 2000 2500 3000 3500 4000

FREQUENCY

Thin lifts

Thick lifts

TEMPERATURE INFLUENCES

WORKABILITY

Allows less rolling time

tCloudy, windy day

Sunny day

Allows more rolling time

138

tLow temp.

High temp.

•

27577 140Temperature, ° F

o27577 140Temperature, of

o

>-- >-II) -0 II)0 0II) 0

II)

> >

II)

ooII)

-II)ooII)

>

,"­ ,

"­"­ ......

OrI9;"41 J ",,­......

"" "o 77 140Temperature, of

275

-- ----Original? - - - ....

> L.1....J..1 ..L1 ....J1:.....-... -__...._-----.J...,o 77 140 275

Temperature, of

150

-CJQ.~

>-- 145.-enc:CI>0

140

MIXTURE TEMPERATURES OFTEN TOO LOWFOR COMPACTION

r-Maximum Theoretical Density =151.4 pcf-L. _

~MinimumSpecificationDensity =143.8 pcf

STANDARD DRT COMPACTION

200

en 150Q.~

.c-coc:CI> 100..-(/)

CI>--enc: 50CI>I->-..

0

(')

(')

(')

(')

8

o I I I I I I

150 175 200 225 250Compaction Temperat ure. of

140

CEISATION REQUIREMENTS

RKOIIIIMftdid IIInImuln LIlyciown Temper.ture.... Temp. 112" 314" 1" 1·112" 2" ,".nd Gr..t.r

20-32 285'+32·..0 305 295 280+"0-50 310 300 285 275+50-&0 310 300 295 280 270+80-70 310 300 290 285 275 285+70-80 300 290 285 280 270 265+80-90 290 280 275 270 265 280+90 280 275 270 285 280 255

Roiling time.min. .. 8 8 12 15 15

I Inc,.... by 15· wh.n plec:ement I. on be•• 011 lubb... cont.lnlng frozen moisture.

141

ROLLING PATTERNS

A single pattern cannot be designed.

Pattern should be developed on a test strip.

Use nuclear gage for monitoring test strip densification.

Determine core density after construction.

DecompactionReading

-....,

Passes

142

GUIDELINES ROLLING PATTERNS

General Rule apply the heaviest load or energy level

possible at the highest temperature possible

without overstressing the mixture

Roll as close to the paver as possible

FIRST PASS

• Vibratory mode

• Combination mode

• Static mode

SUBSEQUENT COMPACTION PASSES

Compact in vibratory mode

FINISH ROLLING

Use static mode

143

Vibrate only while moving.

EDGE ROLLING

ROLLING THIN LIFTS

Start at outer edge with 2 to 4-inch overhang

ROLLING THICK LIFTS

Start 12 to 15 inches from outside edge

JOINT ROLLING

Seldom produces uniform joint density

Second lane usually has higher density

TYPES

• Full width paving - no joint

• Echelon paving - hot joint

144

JOINT ROLLING PROCEDURE

Roll joints directly behind paver

Static Rollers - First pass: overlap 6 in. onto hot side

Vibratory Rollers - First pass: overlap 6 in. onto cold side

or

First pass completely on hot side

but 3 in. away from cold side

OBJECTIVE

COMPACTION CONTROL

To aid in achieving desired density (engineering properties)

and vo id conten t

145

MINIMUM SPECIFICATION

Average density should be equal to or greater than 97 percent of maximum

laboratory density with no individual determination less than 95 percent.

Voids in the mineral aggregate (VMA) should be:

MAX. AGGREGATESIZE. INCHES

1-1/2

1

3/4

1/2

3/8

Air voids should be

3-5% for surfaces

3-8% for bases

MINIMUMVMA, %

12

13

14

15

16

Need to establish a minimum compaction temperature

- density

- engineeriog properties

146

MAJOR CHANGES

Skid Resistant Aggregates

Master Gradings

Design

Stabil ity

Equipment

Stockpiling

In-Place Density

147

SKID RESISTANT AGGREGATES

1. Incorporate Provisions ofAdministrative Order for PolishValue for Coarse Aggregates.

2. Differential wear when requiredby Plan Note.

148

MASTER GRADINGS

1. Based on 100% Aggregate.

2. Required %, No. 10 - No. 40 Sieve

3. Required %Passing No. 200

4. Tolerances apply to extractiontest except Minus 200 and %Asphalt.

149

DESIGN

1. Master Grading Applicable toDesign by Weight or Volume.

Volume Design required of BulkSpecific Gravity varies morethan 0.300.

2. Option for Contract to providedesign.

150

STABILITY

Increase to 35

151

EQUIPMENT

1. Drum-Mixer Requirements

2. Contractor's Responsibility

152

•

STOCKPILING

1. Basically same for Weigh Batchand Continuous Mixing Plants

2. Drum-Mix PlantsMaximum tolerance of + 8percentage points .

153

IN PLACE DENSITY

1. Required for all mixtures.

2. Cores, pavement sections,nuclear

154

PROJECT 285

Asphalt Concrete Mixture Designand Specification

155