Highway Engineering TRAN 3001 Lecture 8

8/9/2019 Highway Engineering TRAN 3001 Lecture 8

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TRAN3001Highway Engineering

Lecture 8Structural Design

Flexible Pavement Design

The Design Process: CumulativeEquivalent Standard Axle Loading

Road Note 3C!R

!ituminous Sur"acings


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Structural Design

Flexible Pavement The Design Process The (orecast! cu"ulati#e e$ui#alent stan%ar%a&le (ESAL! loa%ing on a 'a#e"ent or a gi#engrowth rate (g! 'ercent o#er a %esign lie o nyears can e co"'ute% ro" the or"ula)

ESAL" # ESAL $ %& g'(()n

This loa%ing an% orecast a''lies to *e&ile aswell as rigi% 'a#e"ents+ This co"'letes the,rst ste' in the %esign 'rocess+


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Structural Design (-ont.%!

Flexible Pavement (Cont’d) The Design Process (-ont.%!

The ne&t ste' is assessing the sugra%e

strength an% this is %one y "eans o a soiltest the -aliornia earing Ratio (-R!+

The -R test is entirely e"'irical an% %oes

not "easure any asic 'ro'erty o the soil+ The results are only a''licale to the%esign 'roce%ure+4or 'ur'oses o 'a#e"ent %esign the

sugra%e "oisture content is esti"ate%+


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Flexible Pavement (Cont’d) The Design Process (-ont.%!4or %esigning the thic5ness o a roa%

'a#e"ent the strength o the sugra%eshoul% e ta5en as that o the soil at a"oisture content e$ual to the wettest"oisture con%ition li5ely to occur inthe sugra%e ater the roa% is o'ene% totrac+ Sugra%e "oisture con%itions un%eri"'er"eale roa% 'a#e"ents can e

classi,e% into three "ain categories)


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Flexible Pavement (Cont’d) The Design Process (-ont.%!-ategory (1!) Sugra%es where the water

tale is suciently close to the groun%surace to control the sugra%e "oisturecontent+

This inclu%es areas where the water tale is

"aintaine% y rainall i+e+ when rainalle&cee%s e#a'otrans'iration+

The water tale can also e "aintaine% ya ri#er or the sea such as coastal stri's

an% *oo% 'lains+


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Flexible Pavement (Cont’d) The Design Process (-ont.%!-ategory (6!) Sugra%es with %ee' water

taleswith rainall sucient to 'ro%uce signi,cantchanges in "oisture con%itions un%er the roa%+

These con%itions occur when rainall e&cee%s

e#a'otrans'iration or at least two "onths othe year an% a#erage annual rainall is ine&cess o 670 ""+


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Flexible Pavement (Cont’d) The Design Process (-ont.%!-ategory (3!) Sugra%es in areas with no

'er"anent water tale near the groun%surace+n these areas the cli"ate is %ry throughout"ost o the year with an annual rainall o

670 "" or less+Locally a#erage annual rainall is aout6600 "" an% the 9:%ay soa5e% -R #aluewhich re'resents saturate% sugra%e

con%itions is co""only s'eci,e%+


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Flexible Pavement (Cont’d) The Design Process (-ont.%! The relationshi' etween "oisture content

%ensity an% strength o the sugra%e soil(-R! is %eter"ine% y laoratory testing+At any gi#en "oisture content the soilstrength can e increase% i the %ensity o the

soil is increase% y %ecreasing its air content+n the laoratory the -R o the soil isoser#e% to increase as the unit weight o thesa"'le is increase% with the "oisture content

5e't constant+


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Flexible Pavement (Cont’d) The Design Process (-ont.%! Thereore a %esign unit weight "ust e selecte%

that corres'on%s to the ("ini"u"! state oco"'action e&'ecte% to e achie#e% in the ,el%+A loa% #ersus 'enetration test is carrie% out inthe laoratory on a s'eci"en o the sugra%e

soil which is at the "oisture content an% %ensitya''ro'riate or the sugra%e in ser#ice+A loa% #ersus 'enetration cur#e is 'lotte% an%co"'are% with the cur#e or the stan%ar%

"aterial+


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Flexible Pavement (Cont’d) The Design Process (-ont.%! The #alues or the stan%ar% "aterial(crushe% li"estone! estalish the scale orassessing soil strength+

The -R #alue otaine% is "ulti'lie% y100 so that it is e&'resse% as a 'ercentage+

-R #alues can also e "easure% in situ or,ne:graine% soils where unli5e granularsoils the results are e$ui#alent to thelaoratory test results on which the -R

#alues are ase%+


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4ine:graine% soils ty'ically ha#e low -R

#alues o 6 2 7; whereas well:gra%e%coarse:graine% soils can ha#e #alues ine&cess o 80;+


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A "ini"u" -R o 30 'er cent is re$uire%

or the suase layer an% well:gra%e%san%y gra#els an% si"ilar coarse:graine%"aterials are suitale+


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Flexible Pavement (Cont’d) The Design Process (-ont.%


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The eight (8! trac classes an% si& (>! sugra%estrength classes as shown in the Roa% Note are liste%

hereun%er)Trafc Classes (106 S!"s)

T1 ? 0+3 T7 3+0 2 >+0

T6 0+3 2 0+@ T> >+0 2 10

T3 0+@ 2 1+7 T@ 10 2 1@ T9 1+7 2 3+0 T8 1@ 2 30


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Subgrade Strengt# Classes (C$%

&)

S1 6

S6 3 2 9

S3 7 2 @

S9 8 2 19

S7 17 2 6

S> 30B


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S'mbols used on t#e C#art

Sur"ace

+lexi.le !ituminous Sur"ace 0ranular Road.ase

Selected +ill

!ituminous Sur"ace 0ranular Su..ase

%1earing and !ase Course)


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Flexible Pavement (Cont’d)itu"inous Suracing


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Flexible Pavement (Cont’d)

itu"inous Suracing (-ont.%!

Trac is in %irect contact with the HCAwearing course which "ust e o high$uality an% ha#e 're%ictale 'eror"ance+

Ty'ically HCA wearing courses nee% to

ha#e the ollowing characteristics)•high resistance to %eor"ation

•high atigue an% strain resistance

(*e&iility!


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!•sucient stiness to re%uce stresses in

the un%erlying layers to acce'tale le#els•high resistance to en#iron"ental%egra%ation i+e+ goo% %uraility which"aintains the s"ooth running surace

while 'rotecting the un%erlying layers•low 'er"eaility to 're#ent the ingresso water which can %a"age the

un%erlying layers


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!•goo% wor5aility to allow a%e$uate

co"'action %uring construction•sucient surace te&ture to 'ro#i%e goo%s5i% resistance 'articularly in wet weather •'re%ictale 'eror"ance

The "aterials an% the relati#e 'ro'ortionso each are 5ey consi%erations in HCA "i&%esign+ +


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2ix Com$onents

The ty'es o HCA "ost re$uently use%locally an% in tro'ical countries are"anuacture% in an as'halt 'lant y hot:"i&ing a''ro'riate 'ro'ortions o the

ollowing "aterials)•coarse aggregate %e,ne% as "aterialha#ing 'articles larger than 6+3>"" (9+@7

"" in accor%ance with AASHT/!


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2ix Com$onents %Contd)

•,ne aggregate %e,ne% as "aterial ha#ing'articles less than 6+3>"" an% larger than0+0@7 ""•,ller %e,ne% as "aterial ha#ing 'article

sies less than 0+0@7"" which "ayoriginate ro" ,nes in the aggregate or ea%%e% in the or" o ce"ent li"e orgroun% roc5 the latter eing "ore

co""only use% locally+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2ix Com$onents %Contd)

•a 'enetration: gra%e itu"en with#iscosity characteristics a''ro'riate or thety'e o HCA the cli"ate an% the loa%ing

con%itions where it will e use%+42A T5$es Two generic ty'es o HCA are co""onlyuse% in countries li5e Trini%a% an% Toago

with tro'ical cli"ates)


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Structural Design (-ont.%!Flexible Pavement (Cont’d)

itu"inous Suracing (-ont.%!42A T5$es %Contd) •!s#altic Concrete (!C) which is y

ar the "ore co""only use% "i&+ Tracstresses are trans"itte% "ainly throughan aggregate structure that has acontinuous 'article sie %istriution+ This gi#es the "a&i"u" %ensity aterco"'action howe#er such a %ensestructure "a5es A- sensiti#e to errors in

the co"'osition o the "i&+


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Structural Design (-ont.%!Flexible Pavement (Cont’d)

itu"inous Suracing (-ont.%!42A T5$es %Contd) •ot %olled !s#alt *ixes in which trac

stresses are 'asse% through the ,nes=,ller=itu"en "atri&+ n these "i&es theaggregate 'article sie %istriution is%iscontinuous or ga':gra%e%+

t is less use% on hea#ily trac5e% roa%san% still reco""en%e% on resi%ential roa%sas it is less sensiti#e to 'ro'ortioning"a5ing it easier to "anuacture lay an%

co"'act than A-+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%! AC Design ConsiderationsAs'haltic -oncrete (A-! has to e %esigne%to resist %eterioration cause% y three "ainailure "o%es) "atigue crac6ing, $lasticde"ormation and loss o" s6id resistance in

the suracing +-rac5ing is as a result o ther"al or trac:in%uce% strains or a co"ination o oth+/ne way o i"'ro#ing the %uraility o the

A- is to increase the itu"en content+


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Structural Design (-ont.%!Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%! AC Design Considerations %Contd) This re%uces the air #oi%s content an%

rittleness+ Any surace crac5ing in theitu"en:rich "i& is li5ely to re"ain shallow or aconsi%erale ti"e+Howe#er using a "i& too rich in itu"en

intro%uces a ris5 o ailure through 'lastic%eor"ation+ Fn%er hea#y trac the air #oi%scontent can e re%uce% to a critical le#el atwhich 'lastic %eor"ation occurs relati#ely

ra'i%ly+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!

AC Design Considerations %Contd)


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!

AC Design Considerations %Contd)

Loss o s5i% resistance or surace te&ture %ueto the 'olishing action o #ehicle tyres can%e#elo' ecause o the use o the wrong ty'eo aggregate (low resistance to 'olishing!

incorrect aggregate 'article sie as well aswrong in%er content an% #iscosity whichresults in 'rogressi#e e"e%"ent o theaggregate in the suracing+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design

There are "any "etho%s a#ailale or A-(as'haltic concrete! "i& %esign which#ary in the sie o the test s'eci"enco"'action an% other test s'eci,cations+ The Carshall "etho% o "i& %esign is theone "ost co""only use% +


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)

The Carshall "etho% is suitale or the %esignan% ,el% control o A- "i&es containing

aggregates with a "a&i"u" sie o u' to67""+ Aggregates are 're'are% an% len%e% togi#e sa"'les which conor" to a selecte%'article sie %istriution+ nitial "i& %esignsa"'les are 're'are% that co#er a range oitu"en contents+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd) The sa"'les are suGecte% to a le#el oco"'action which is relate% to thee&'ecte% trac in ter"s o ESALs to ecarrie% in the %esign lie o the A- layer(s!+

The 'ro'erties o the co"'acte% sa"'lesinclu%ing ul5 %ensity air #oi%s stailityan% %eor"ation characteristics un%erloa% are then %eter"ine%+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd) the "i& 'ro'erties %o not "eet thes'eci,e% %esign criteria the "i& "uste reor"ulate% an% the tests re'eate%until an acce'tale %esign is estalishe%+

Sucient $uantities o coarse aggregate,ne aggregate ,ller an% itu"enre'resentati#e o those to e use% on the

'roGect nee% to e otaine%+


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This will allow tests to e re'eate% i

necessary or testing o %ierent aggregategra%ings+Sie#e analysis is carrie% out on re'resentati#esa"'les o each aggregate source an% ,ller+Fsing the results o the sie#e analysisotaine% or each source o aggregate alen% is co"'ute% which conor"s to the

s'eci,e% aggregate 'article sie %istriution+


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Sa"'les o itu"en shoul% e ta5en ro"either the storage tan5 or the %eli#erytan5er+ The ollowing 'ro'erties o theitu"en are "easure%)

•Penetration at 67-+•Sotening 'oint (the te"'erature at whichthe

'enetration is assu"e% to e 800!+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)•Iiscosity at a''ro&i"ately 107- to 117-137- an% 1>0-+

The results o the tests are 'lotte% on aitu"en

test %ata chart which in%icates thete"'erature:#iscosity characteristics o theitu"en an% enale selection o the ranges oi%eal "i&ing an% co"'action te"'eratures+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)A series o test s'eci"ens are 're'are% or arange o %ierent itu"en contents (ty'ically7 len%s with 3 sa"'les each or a total o 17s'eci"ens! which s'an the e&'ecte% %esign

#alue+ The e&'ecte% %esign #alue is esti"ate% ro"e&'erience or a or"ula ase% on aggregategra%ation an% asor'tion o itu"en+

S l D i (- .%!


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd) The test s'eci"ens are transerre% to the Carshall

co"'action a''aratus an% co"'acte% y thes'eci,e% nu"er o lows o the Carshall ha""er%e'en%ing on the ESAL o the e&'ecte% trac+ The "i& 'ro'erties to e %eter"ine% ro" the test

s'eci"ens are the .ul6 s$eci7c gravit5 %0), $ercent air voids %8v), $ercent volume o" .itumen%8.), $ercent voids in the mineral aggregate %82A)and $ercent voids 7lled 9ith .itumen %8+!)

S l D i (- .%!


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ICA I# I I

I

S$ecimen Phase Diagram

A

Bitumen

Filler

Fine Aggregate

Air Voids

Coarse Aggregate

St t l D i (- t.%!


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)I# is the ratio o the #olu"e o air #oi%s to

the total s'eci"en #olu"e e&'resse% as a'ercentage+Si"ilarly I is the 'ercent o the #olu"e oitu"en to the total #olu"e+

ICA is the #olu"e o #oi%s in theaggregates which is the su" o the air #oi%san% the itu"en #olu"e) ICA J I# B I

St t l D i (- t.%!


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)I4 is the ratio o the 'ercent itu"encontent in the "i& (I! to the ICA (#oi%s inthe "ineral aggregate ra"ewor5! e&'resse%as a 'ercentage+

The "i& 'ro'erties are use% to %eter"ineCarshall staility an% *ow+ The Carshall staility o a test s'eci"en is the"a&i"u" loa% re$uire% to 'ro%uce ailure

un%er stan%ar% test con%itions+

St t l D i (- t.%!


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Flexible Pavement (Cont’d)

itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd) there is a slight #ariation ( B >+9 ""!etween the thic5ness o the test s'eci"enan% the stan%ar% s'eci"en thic5ness"easure% staility #alues are correcte% tothose which woul% ha#e een otaine% i the

s'eci"ens ha% een e&actly >3+7 ""+ The loa% is a''lie% at a constant strain (70"" 'er "inute! an% the #ertical%eor"ation o the s'eci"en is "easure%+

St t l D i (- t.%!


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd) The %eor"ation at the ailure 'oint e&'resse% in

units o 0+67 "" is calle% the Carshall *ow #alueo the s'eci"en+ The staility #alue *ow #alue an% I4 arechec5e% with the Carshall "i& %esign

s'eci,cations+ The a#erage #alue o the 'ro'erties (K I# IICA an% I4! are then %eter"ine% or each "i&an% the ollowing 7 gra'hs 'lotte%)

St t l D i (- t.%!


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•itu"en content #ersus (correcte%! Carshallstaility

•itu"en content #ersus Carshall 4low

•itu"en content #ersus 'ercentage o #oi%s(I#! in the total "i&

•itu"en content #ersus 'ercentage o #oi%sin the "ineral aggregate ,lle% with itu"en

(I4!

St t l D i (- t.%!


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Structural Design (-ont.%!S 4 It l T

a 0 C wi

li

t y

I F

4 n

t<

t+

itu"en -ontent (; y weight o total "i&!

Ty'ical Carshall Test Data

St t l D i (- t.%!


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•itu"en content #ersus unit weight orul5 s'eci,c gra#ity The o'ti"u" itu"en content or the"i& %esign is %eter"ine% y ta5ing thea#erage #alue o the ollowing threeitu"en contents oun% ro" the gra'hs)

St t l D i (- t.%!


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•itu"en content corres'on%ing to"a&i"u" staility•itu"en content corres'on%ing to

"a&i"u" ul5 s'eci,c gra#ity•itu"en content corres'on%ing to the"e%ian o %esigne% li"its o 'ercent air#oi%s (I#! in the total "i& (usually 9;!


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Structural Design (-ont.%! Ty'ical Carshall Design -riteria

*ixCriteria

"ig#t Trafc(+ 10, S!"s)

*edium Trafc(10, - 106 S!"s)

eav' Trafc(. 106 S!"s)

*in/ *ax/ *in/ *ax/ *in/ *ax/

-o"'action

(nu"ero lowson eachen% o

thesa"'le!

37 70 @7

Staility("ini"u

"!

6669 N 333> N >>@6 N

4low(0+67 ""

!8 60 8 18 8 1>

Percent

One standard Marshall mix design procedure is:


http://www.pavementinteractive.org/article/marshall-mix-design/equivalent-single-axle-loadhttp://www.pavementinteractive.org/article/marshall-mix-design/equivalent-single-axle-load


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd) The Carshall test results re*ect tren%s whichare co""on to "ost laoratory tests oro'ti"u" itu"en content as well as actual

roa% suracing eha#iour as ollows)• The unit weight o the "i& increases withincreasing itu"en content until a "a&i"u"#alue is reache% ater which the unit weight%ecreases+



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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)• The staility o the "i& increases withincreasing itu"en content until a"a&i"u" #alue is reache% ater

which the staility %ecreases+

Kenerally the o'ti"u" itu"encontent or staility is close to theo'ti"u" itu"en content or unit

weight+



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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)• The *ow #alue increases as the itu"encontent increases+

The rate o %eor"ation is slow at lowitu"en contents ut increases ra'i%ly at

high itu"en contents+ This result is in%icati#e o actual

roa%way 'eror"ance as suracings withhigh *ows %eor" easily un%er trac loa%s+


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Flexible Pavement (Cont’d)itu"inous Suracing (-ont.%!2arshall 2ix Design %Contd)• The 'ercentage o #oi%s in the total "i&%ecreases with increasing itu"en content

until a #alue is reache% at which itegins to le#el o+

The ITC 'ercentage is critical withres'ect to %uraility as too high a #alue"a5es the itu"en an% itu"en:aggregate on% "ore susce'tile to

attac5 y air an% water+


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Too low an air #oi%s content"a5es the suracing "ore li5ely tolee% un%er trac+• The 'ercentage o #oi%s ,lle% withitu"en increases with increasingitu"en content until a "a&i"u" isreache% ater which it le#els o+


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The rate o increase is astest at lowitu"en contents ater which the rate%ecreases until it le#els o at a highitu"en content+

Documents

Highway Engineering TRAN 3001 Lecture 8