transportation research asphaltig - ctr...
TRANSCRIPT
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-
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OUST COLLfCTOI...._ _--, -_. "_ ...
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OUOAnOM COHnOl UNIT---- _......- ...-- --_ ..--...._-----...._.._-_.--..
-.. ~...._~- .......-...-- -_.... ---_.-- .... ,---
.......--- .. ~_ ..--_...... -,.....
...._-- ...,... - ............ - -._.
••_.........._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