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GUIDELINES FOR THE DESIGN
OF
FLEXIBLE PAVEMENTS
(Third Revision)
DRAFT
THE INDIAN ROADS ONGRESS
OTOBER !"##
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ONTENTS
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I$e% No& Des'ri$ionP*e
No&
1 Introduction 4
2 Scope of the Guidelines 5
3 Recommended Method of Design 6
4 Traffic
4!1 General
4!2 Traffic gro"th rate #
4!3 Design life $
4!4 %ehicle damage factor $
4!5 Distri&ution of commercial traffic o'er the carriage"a( 11
4!6 )omputation of design traffic 13
5 Su&grade 14
5!1 Su&grade )*R 14
5!2 +ffecti'e )*R 1
5!3 Determination of resilient modulus 1
6 ,a'ement )ompositions 1$
6!1 General 2-
6!2 .n&ound Su&&ase la(er 21
6!2!2 *ound Su&&ase la(er 22
6!3 *ase la(er 23
6!3!1 .n&ound *ase la(er 23
6!3!2 *ound *ase la(er 23
6!4 *ituminous surface la(er 26
,a'ement Design 2#
!1 General 2#!2 Design Method 2$
# ,a'ement Thic/ness and )omposition 3-
#!1 ,a'ement Thic/ness Design 3-
Thic/ness design for traffic upto 1 msa 33
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0 *ituminous pa'ement "ith Granular *ase and Granular Su& *ase
**ituminous pa'ements "ith cemented &ase and cementitious su&&ase ha'ing 1--mmof aggregate interla(er for crac/ relief! .pper 1--mm of the cementitious su&&ase is
the drainage la(er
)
*ituminous pa'ements "ith cemented &ase T and cementitious su&&ase "ith S0MI
at the interface of &ase and the &ituminous la(er! .pper 1--mm of the cementitioussu&&ase is the drainage la(er
D*ituminous pa'ements "ith foamed &itumen &itumen emulsion treated R0,
aggregates o'er 25-mm )ementitious su&&ase top 1--mm is the drainage la(er
+*ituminous pa'ements "ith cementitious &ase and granular su&&ase "ith crac/ relief
la(er of aggregate la(er a&o'e the cementitious &ase
$ Internal drainage in ,a'ement
1- Design in rost 0ffected 0reas
0nneure 1 Rutting atigue +7uations
i Rutting in su&grade and granular la(er
ii Rutting in the &ituminous la(er
iii atigue resistant &ituminous la(er
0nneure 2 8or/ed +amples Illustrating the Design Method
i *ituminous pa'ement "ith untreated granular la(er
ii*ituminous pa'ement "ith cementitious &ase and cementitious su&&ase "ith
aggregate interla(er of 1--mm
iii*ituminous pa'ement "ith cementitious &ase and cementitious su&&ase "ith S0MI
la(er o'er cementitious &ase
i' *ituminous pa'ement "ith &ase of fresh aggregates or Reclaimed asphalt pa'ementR0, treated &itumen &itumen emulsion and cementitious su&&ase
' Design of flei&le pa'ement for 3--msa of traffic
'i Design eample of perpetual ,a'ement
0nneure 3 +7ui'alence of thic/ness of &ituminous mies of different moduli
0nneure 4 ,reparation of 9a&orator( Test Specimens
0nneure 5 Drainage la(er
0nneure 6Recommended T(pe and Thic/ness of *ituminous "earing courses for lei&le
,a'ement .nder Different Situations
0nneure )riteria or Selection of Grade of *itumen or *ituminous )ourses
0nneure # Resilient Modulus of a Granular Material
0nneure $ )onstruction of pa'ement la(ers "ith sta&ili:ed materials
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ABBREVIATIONS
00S;T< = 0merican 0ssociation of State ;igh"a( and
Transportation
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#The design of flei&le pa'ement in'ol'es the interpla( of se'eral 'aria&les> such as
ale loads> characteristics of traffic> climate> terrain and su&=grade conditions! 8ith a
'ie" to ha'e a unified approach for "or/ing out the design of flei&le pa'ement in the
countr(> the IR) first &rought out guidelines in 1$-! Those "ere &ased on )alifornia
*earing Ratio )*R method! To handle large spectrum of ale loads> those
guidelines "ere re'ised in 1$#4 follo"ing the e7ui'alent standard ale load
concept! In thisapproach> the pa'ement thic/ness "as related to the cumulati'e num&er
of standard ales to &e carried out for different su&=grade strengths! Those guidelines used an
empirical approach &ased on a large etent of past eperience and ?udgment of high"a(
agencies! Design cur'es "ere de'eloped for traffic up to 3- million standard ales!
1!2 The guidelines "ere re'ised again in 2--1 "hen pa'ements "ere re7uired to &e
designed for traffic as high as 15- million standard ales! 0 semi=mechanistic approach
"as used as a result of the M tridem and multi=ale 'ehicles ha'e increased man( fold and hea'ier ales
are common! +perience has &een gained on use of ne" forms of construction and
materials such as Stone Mastic 0sphalt> modified &itumen> foamed &itumen> &itumen
emulsion> "arm asphalt> cementatious &ases and su& &ases! )on'entional as "ell as
commerciall( a'aila&le soil sta&ili:ers are &eing successfull( used in trial sections! In
terms of su&grade support as "ell as su&&ase! In terms of su&grade support as "ell as
su&&ase strength changes are &eing noticed "ith a'aila&ilit( of con'entional as "ell as
commerciall( a'aila&le soil sta&ili:ers! 0ttention is no" focused on high fatigue
resistant &ituminous mies high 'iscosit( of &inders "ith a 'ie" to construct a high
performance long life &ituminous pa'ement!
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1!4 The con'entional construction material li/e aggregates is &ecoming progressi'el(
scarce on account of en'ironmental concerns as "ell as legal restrictions on 7uarr(ing
"hile the construction acti'it( has epanded phenomenall(B this has shifted focus from
large scale use of con'entional aggregates to use of local and marginal materials in
construction!
It is recogni:ed that research as "ell as performance trials ha'e not &een etensi'e in
India for some of the ne" materialsB hence these ha'e &een included in the guidelines>
the details of "hich are &ased on the etensi'e performance reports and current
practices in 0ustralia and South 0frica!
0ccordingl( this re'ision of IR) 3 aims at incorporating some of the ne" and
alternate materials and current design practices!
!& SOPE OF THE GUIDELINES
2!1! These guidelines "ill appl( to the design of ne" flei&le pa'ements for
+press"a(s> Cational ;igh"a(s> State ;igh"a(s> Ma?or District Roads and other
categories of roads predominantl( carr(ing motori:ed 'ehicles!
2!2! or the purpose of the guidelines> flei&le pa'ements include flei&le pa'ements "ith
*ituminous surfacing o'er
i granular &ase and su&&ase
ii cementitious &ase and cementitious su&&ase
iii Reclaimed asphalt pa'ement treated "ith foamed &itumen &itumen emulsion!
The damaged &ituminous la(ers of eisting pa'ements can &e completel( milled and it can
&e reused "ith suita&le treatment after the restoration of the drainage and the separation
la(ers in the light of Indian and International eperience! ;otcold insituplant rec(cling of
the damaged &ituminous mi can &e adopted for pa'ement construction after a thorough
stud( in "hich the pa'ement design parameters are determined from la&orator( tests!
2!3! These guidelines do not include charts for strengthening of eisting pa'ements>
for "hich the o'erla( design procedure as per IR) #1=1$$1#> shall appl(!
2!4! The guidelines ma( re7uire re'ision from time to time in the light of future
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eperience and de'elopments in the field! To"ards this end> it is suggested that all the
organi:ations intending to use the guidelines> should /eep a detailed record of (ear of
construction> su&grade )*R> soil characteristics including resilient modulus>
pa'ement composition and specifications> traffic> pa'ement performance> o'erla(
histor(> climatic conditions> etc! andpro'ide feed&ac/ to the Indian Roads )ongress!
+ REOMMENDED METHOD OF DESIGN
3!1Gener,
3!1 The IR) 3=2--1 "as &ased on a Mechanistic +mpirical approach> "hich
considered the life of pa'ement to last till the fatigue crac/ing in &ituminous surface
etended to 2- E of the pa'ement surface area or rutting in the pa'ement reached the
le'el of 2- mm> "hiche'er happened earlier! The same approach and the criteria are
follo"ed in these re'ised guidelines as "ell! The crac/ing and rutting models in IR)
32--1"ere &ased on the findings of the research schemes of Ministr( of Road
Transport ;igh"a(s> Go'ernment of India under "hich pa'ement performance data
"ere collected from all o'er India &( academic Institutions and )entral Road Research
Institute to e'ol'e the fatigue and rutting criteria for pa'ement design using a semi=
anal(tical approach! In the a&sence of an( further research in the field to modif( or
refine these models> the same models are considered applica&le in these guidelines as
"ell! These re'ised guidelines> ho"e'er> aim at epanding the scope of pa'ement
design &( including alternate materials li/e cementitious and reclaimed 0sphalt
materials> and su&?ecting them to anal(sis using the soft"are ,0%+ de'eloped under
the Research Scheme R=56 for la(ered s(stem anal(sis! The material properties of these
alternate materials> such as Resilient Modulus> "ere etensi'el( tested in la&oratories in
the countr(> especiall( IIT> Aharagpur! The field e7ui'alents of these la&orator( 'alues
"ere selected on the similar lines on "hich some other countries> such as 0ustralia and
South 0frica> ha'e &ased their national standards! The performance of the actual
pa'ements constructed in the countr( "ith alternate materials see 0nne!!also holds
promise! 0s far as the anal(sis of the la(ered s(stem is concerned> the output of ,0%+
seems to &e in close agreement "ith those of commerciall( a'aila&le standard
soft"ares! ,0%+ has &een su&se7uentl( modified to include se'en la(ers as against
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four in the original ,rogram and the ne" soft"are IIT,0%+ has resulted!
3!2 The eperience on a num&er of high 'olume high"a(s designed and constructed
during the last decade using the guidelines of IR) 3=2--1 as reported in 'arious
literature sho"s that the most common mode of distress has &een flushing and rutting in
the &ituminous la(er 35> 3 and 45! Surface crac/ing of the &ituminous la(er i!e! the
top do"n crac/ing "ithin a (ear or t"o of construction is also reported from different
parts of India 26> 3$> and 4! ,u&lished literature on fatigue and rutting of different
t(pes of &ituminous mitures ha'e helped in &etter understanding of these
pro&lems 1-> 12> 15> 25> 2$> 3-> 34 and 3! The present guidelines strongl(
recommend that these pro&lems need serious consideration! *ituminous mi design
needs to &e considered an integral part of pa'ement design eercise "ith a 'ie" to
pro'iding fatigue resistant mies in the &ottom &ituminous la(er to eliminate &ottom up
crac/ing> rut resistant mies for surface &ituminous la(ers to eliminate rutting on
the surface> and higher 'iscosit( grade &itumen in the surface la(er to eliminate top
do"n crac/ing!
3!3 The re'ised guidelines recommend &ound su& &ases and &ases! Such &ound
la(ers "ould crac/ immediatel( after construction due to shrin/age and in such
condition> their strength reduces to half! ;o"e'er> e'en in crac/ed conditions the( ha'e
enough residual strength for use as su& &ase and &ase la(ers pro'ided three conditions
are satisfied> 'i:> i the crac/s are not allo"ed to propagate to the upper &ituminous
la(er> ii the design strength properties Resilient Modulus of such la(ers is
?udiciousl( selected> "hich can ensure long term performance as a structural la(er in the
pa'ement and iii their long term &eha'ior till failure> i!e! the fatigue &eha'ior> is
anal(:ed on the same principles that are applied for rigid pa'ements! Due to lo" le'el
of stresses at the su& &ase and &ase le'els> the &ound materials used in these la(ers need
to ha'e a considera&l( lo" compressi'e strength and hence the Resilient Modulus>
"hich can &e successfull( achie'ed e'en &( sta&ili:ing local and marginal materials!
8hile their strength ma( &e lo"> it is essential to ensure a reasona&le le'el of dura&ilit(
&ecause the crac/ed la(ers "ill permit ingress and egress of "ater su&?ecting the la(er
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to F"etting@ and Fdr(ing@ alternatel(!
3!4 These guidelines recommend that for a &etter performing pa'ement the follo"ing
aspects should necessaril( &e considered in design
i Design period should &e for more than fifteen (ears!
ii +ffecti'e )*R of su&=grade should &e the &asis for pa'ement design!
iii atigue anal(sis of &ound &ases should &e carried out for each t(pe
ales> a single ale "ith single "heels & single ale "ith dual
"heels c tandem ale and d tridem ales!
i' Rut resistant mies should &e used for surface la(er!
' atigue resistant mies should &e used for &ottom &ituminous la(er!
'i Surface la(er should &e resistant to top do"n crac/ing!
'ii Reclaimed asphalt material should &e utili:ed as a pa'ement &ase
la(er after treating "ith emulsion or foamed &itumen
'iii9ocall( a'aila&le soil and aggregate should as far as possi&le> &e used
as su&&ase and &ase after appropriate sta&ili:ation!
i Drainage la(er should &e ade7uatel( designed and pro'ided for!
0 perpetual pa'ement ha'ing full depth &ituminous la(ers is possi&le
to &e designed in appropriate situations!
+ach of the items listed a&o'e has &een discussed in these guidelines at appropriate
places!
3!5 In these guidelines onl( 9oad associated mode of failure has &een considered as
en'ironmental effects are &uilt=in in the cali&ration of rutting and fatigue e7uations from
pa'ement performance! ,roperties of materials used in flei&le pa'ements design are
also discussed!
-& TRAFFI
- Gener,
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4!1!1! The recommended method considers traffic in terms of the cumulati'e num&er
of standard ales #-/C to &e carried &( the pa'ement during the design life! or
estimating design traffic> the follo"ing information is needed
i Initial traffic after construction in terms of num&er of
)ommercial %ehicles per da( )%,D!
ii Traffic gro"th rate during the design life in percentage!
iii Design life in num&er of (ears!
i' Spectrum of ale loads!
' %ehicle damage factor %D!
'i Distri&ution of commercial traffic o'er the carriage"a(!
4!1!2! or the purpose of structural design> onl( the num&er of commercial 'ehicles
ha'ing gross 'ehicle "eight of three tones 3-/C or more and their ale=loading is
considered!
4!1!3! To o&tain a realistic estimate of design traffic> due consideration should &e gi'en
to the eisting traffic or that anticipated &ased on possi&le changes in the road net"or/
and land use of the area ser'ed> the pro&a&le gro"th of traffic and design life!0ssessment
of a'erage traffic should normall( &e &ased on se'en=da(=24=hour count made in accordance
"ith IR) $=1$2 Traffic )ensus on Con=.r&an RoadsH! The actual 'alue of gro"th rate Fr@ of
hea'( commercial 'ehicles should &e determined&
-&! Tr..i' *ro/$h r$e
4!2!1 Traffic gro"th rates should &e estimated
1 *( stud(ing the past trends of traffic gro"th> and
2 *( esta&lishing econometric models> as per the procedure outlined in
IR) guidelines!
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4!2!2 If the data for the annual gro"th rate of commercial 'ehicles is not a'aila&le or if it is less
than 5E> a gro"th rate of 5E shall &e used IR)S,#4=2--$!
-&+ Desi*n ,i.e
4!3!1! The design life is defined in terms of the cumulati'e num&er of standard ales
that can &e carried &efore a ma?or strengthening of the pa'ement is necessar(! It is
also necessar( to o&tain repetitions of different ale loads during the design period for
eamination of the safet( of pa'ements "ith cementitious &ases!
4!3!2 It is recommended that pa'ements for Cational ;igh"a(s and State ;igh"a(s
should &e designed for a minimum life of 15 (ears! +press"a(s and ur&an roads ma( &e
designed for a longer life of 2- (ears or higher using inno'ati'e design adopting high
fatigue &ituminous mies! In the light of eperience in India and a&road> 'er( high
'olume roads "ith design traffic greater than 2--msa and perpetual pa'ements can &e
designed using the principles enshrined in the guidelines! or other categories of roads>
a design life of 1- to 15 (ears ma( &e adopted!
4!3!3 %er( often it is not possi&le to pro'ide the full thic/ness of pa'ement right at the
time of initial construction! If stage construction is adopted> thic/ness of granular
la(er should &e pro'ided for the full design period! In case of cementitious &ases and
su&&ases> stage construction ma( lead to earl( failure &ecause of high fleural stresses
in the cementitious la(er!
-&- Vehi',e d%*e .'$or
4!4!1 Though it is possi&le to determine progression of crac/ing and rutting in
&ituminous pa'ements &( adopting cumulati'e damage principle> field data is not (et
a'aila&le and the concept of e7ui'alent standard ale load repetitions is currentl( the &est
a'aila&le option for thic/ness design of &ituminous pa'ements! In case of cementitious
&ases> spectrum of ale loads should &e used to determine the safet( of cementitious
la(er from premature crac/ing!
4!4!2 The 'ehicle damage factor %D is a multiplier to con'ert the num&er of
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commercial 'ehicles of different ale loads and ale configuration to the num&er of
repetitionsof standard ale load of magnitude #-/C! It is defined as e7ui'alent num&er
of standard ales per commercial 'ehicle! The %D 'aries "ith the 'ehicle ale
configuration> ale loading> direction of tra'el> terrain> t(pe of road and region! The %D
is arri'ed at from ale load sur'e(s on t(pical road sections so as to co'er 'arious
influencing factors> such as traffic mi> mode of transportation> commodities carried> time
of the (ear> terrain> road conditions and degree of enforcement!
4!4!3 The e7uations for computing e7ui'alenc( factors for single> tandem and tridem
ales are gi'en in the follo"ing! The( are used for con'erting different ale load
repetitions into e7ui'alent standard ale load repetitions! Since the %D 'alues in
00S;< Road Test for flei&le and rigid pa'ement are not much different> the computed
%D 'alues are assumed to &e same for pa'ements "ith )ementitious and granular
&ases!
Single ale "ith single "heel on either side 4
65
axle load in kN !! 1
Single ale "ith dual "heels on either side4
#-
axle load in kN !! 2
Tandem ale "ith dual "heels on either side4
14#
axle load in kNJ 3
Tridem ales "ith dual "heels on either side4
224
axle load in kNJ 4
4!4!4! or designing a ne" pa'ement> the %D should &e arri'ed at carefull( &(
carr(ing out specific ale load sur'e(s on the eisting roads! Minimum sample si:e is
gi'en in Ta&le 2! 0le load sur'e( should &e carried out "ithout an( &ias for loaded orunloaded 'ehicles! there ma( &e significant difference in ale
loading in t"o directions of traffic! In such situations> the %D should &e e'aluated
direction "ise for the purpose of design! +ach direction can ha'e different pa'ement
thic/ness for di'ided high"a(s depending upon the loading pattern!
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T0,e ! S%,e si1e .or 2,e ,od s3rve4
To$, n3%0er o.
o%%er'i, Vehi',es
s Per $r..i' d$
Mini%3% er'en$*e
o. 'o%%er'i, Tr..i'
needed $o 0e s3rve4ed
K3--- 2-E
3--- to 6--- 15E
L6--- 1-E
4!4!5 A2,e ,od se'$r3%5 Spectrum of ale load should &e determined for single> tandem>
tridem and multi ale loads for the computation of standard ale loads repetitions for pa'ement
design! or the e'aluation of safet( of the )ementitious la(er from premature crac/ing due to
hea'( loads> cumulati'e fatigue damage anal(sis needs to &e done using the load inter'al of 1-
/C for each ale! or fatigue anal(sis of )ementitious la(er> tandem and tridem ale ma( &e
ta/en as t"o and three single ales respecti'el( &ecause of little o'erlapping of stresses from
other ales!
4!4!6 8here sufficient information on ale loads is not a'aila&le and the pro?ect si:e
does not "arrant conducting an ale load sur'e(> the indicati'e 'alues of 'ehicle damage
factor as gi'en in Ta&le 3 ma( &e used!
TABLE +& INDIATIVE VDF VALUES
Ini$i, $r..i' vo,3%e in $er%s o.
'o%%er'i, vehi',es er d4
Terrin
Ro,,in*6P,in Hi,,4
-=15- 1!5 -!5
15-=15-- 3!5 1!5
More than 15-- 4!5 2!5
-&7& Dis$ri03$ion o. 'o%%er'i, $r..i' over $he 'rri*e/4
4!5!1 0 realistic assessment of distri&ution of commercial traffic &( direction
and &( lane is necessar( as it directl( affects the total e7ui'alent standard ale
load applications used in the design! In the a&sence of ade7uate and conclusi'e data> it
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is recommended that the follo"ing distri&ution ma( &e assumed for design until more
relia&le data on placement of commercial 'ehicles on the carriage"a( lanes are
a'aila&le
(i) Sin*,e8,ne rods
Traffic tends to &e more channeli:ed on single=lane roads than t"o=lane
roads and to allo" for this concentration of "heel load repetitions> the
design should &e &ased on total num&er of commercial 'ehicles in &oth
directions!
ii) T/o8,ne sin*,e 'rri*e/4 rods
The design should &e &ased on 5-E per cent of the total num&er of
commercial 'ehicles in &oth directions! If 'ehicle damage factor in one
direction is higher> the design traffic in the direction of higher %D is
recommended!
(iii) Fo3r8,ne sin*,e 'rri*e/4 rods
The design should &e &ased on 4- per cent of the total num&er of
commercial 'ehicles in &oth directions!
(iv) D3, 'rri*e/4 rods
The design of dual t"o=lane carriage"a( roads should &e &ased on 5 per
cent of the num&er of commercial 'ehicles in each direction! or dual three=
lane carriage"a( and dualfour=lane carriage"a(> the distri&ution factor "ill
&e 6- percent and 45 per cent respecti'el(!
4!5!2 The traffic in each direction ma( &e assumed to &e half of the sum in &oth
directions "hen the latter onl( is /no"n! 8here significant differences &et"een the
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t"o streams occur> pa'ements in each direction "ill &e different and considered
accordingl(!
or t"o "a( t"o lane roads> pa'ement thic/ness should &e same for &oth the lanes e'en
if %D 'alues are different in different directions! or di'ided carriage"a(s> each
direction ma( ha'e different thic/ness of pa'ements if the ale load patterns are
significantl( different!
-&9 o%3$$ion o. desi*n $r..i'
4!6!1 The design traffic is considered in terms of the cumulati'e num&er of standard
ales in the lane carr(ing maimum traffic to &e carried during the design life of
the road! This can &e computed using the follo"ing e7uation
365 1 1Nnr
N A D Fr
+ = JJ!5
8here>
C cumulati'e num&er of standard ales to &e catered for in the design in terms
of msa! 0 Initial traffic in the (ear of completion of construction in terms of the
num&er of )ommercial 'ehicles per da( )%,D!
D 9ane distri&ution factor as eplained in para !5!1!
%ehicle damage factor %D!
n Design life in (ears!
r 0nnual gro"th rate of commercial 'ehicles for 5E annual gro"th rate> r-!-5
The traffic in the (ear of completion is estimated using the follo"ing formula
0 , 1Or JJ 6
8here>
, Cum&er of commercial 'ehicles as per last count!
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Cum&er of (ears &et"een the last count and the (ear of completion of
)onstruction!
7 SUBGRADE
7& Re:3ire%en$s o. BR .or s30*rde
The su&grades consists of the top 5--mm of the em&an/ment made up of in situ material>
select soil> or sta&ili:ed lo" strength in situ material that forms the foundation of a
pa'ement! To a'oid additional densification under traffic causing rutting or deformation
in the pa'ement during its ser'ice life> the su&grade should &e "ell compacted and made
up of materials ha'ing good strength properties in terms of )*R! )ompaction to a
minimum of $ per cent of la&orator( dr( densit( is recommended for
+press"a(s> Cational ;igh"a(s> State ;igh"a(s> Ma?or District Roads and other
hea'il( traffic/ed roads!IR) 36 PRecommended ,ractice for the )onstruction of +arth
+m&an/ments for Road 8or/sP should &e follo"ed for guidance during planning and
eecution of "or/! It is ad'isa&le that the su&grade material should ha'e a minimum
)*R of 5 percent for roads ha'ing traffic of 45- commercial 'ehicles per da( or higher!
)*R should &e tested in la&orator( in accordance "ith IS22- ,art #! The guidelines
for preparation of samples> testing> and acceptance criteria are gi'en in su& paras gi'en
&elo"!
The in=situ )*R of the su& grade soil can also &e determined from the D(namic )one
,enetrometer 6--cone from the follo"ing relation 0STM=D6$51=-$ !
Lo*#"BR;!&-978#! ,o*#"N J!
8here Cmm&lo"
5!1!1 Selection of dr( densit( and moisture content for test specimen
5!1!1!1 The la&orator( test conditions should represent the field conditions as closel( as
possi&le! )ompaction in the field is done at $ percent of la&orator( densit( at moisture
content corresponding to the optimium moisture content! In actual field condition> the
su&grade undergoes moisture 'ariations depending upon local en'ironmental factors>
such as> the "ater ta&le> precipitation> soil permea&ilit(> drainage conditions and the
17
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etent to "hich the pa'ement is "aterproof> "hich affect the strength of the su&grade in
terms of )*R!
0s a general practice> the 'ariation in field moisture is simulated &( soa/ing the
specimens in "ater for four da(s
Soa/ing for four da(s ma( represent an unrealisticall( se'ere moisture condition in
certain cases> "here the climate is dr( throughout the (ear> i!e!> the annual rainfall is of the
order of 5--mm and the "ater ta&le is too deep to affect the su&grade ad'ersel(!
5!1!1!2 Cum&er of tests> design 'alue and tolerance limit
0 minimum of si to eight a'erage )*R 'alues for each soil t(pe along the alignment
"ill &e re7uired for determination of design )*R! The $-thpercentile of these 'alues
should &e adopted as the design )*R such that $-E of the a'erage )*R 'alues are
e7ual or greater than the design 'alue for high 'olume roads such as +press"a(s>
Cational ;igh"a(s> and State ;igh"a(s or other categories of roads> design can &e
&ased on #-thpercentile of la&orator( )*R 'alues!,a'ement thic/ness on ne" roads ma( &e
modified at inter'als as dictated &( the soil changes &ut generall( it "ill &e found
inepedient to do so fre7uentl( from practical considerations!
The a'erage )*R 'alues should &e the a'erage of at least three samples remoulded
on the same densit( and moisture content! The maimum permissi&le 'ariation
"ithin the )*R 'alues of the three specimens should &e as indicated in Ta&le 1!
TABLE #& PERMISSIBLE VARIATION IN BR VALUE
BR (er 'en$) M2i%3% vri$ion in BR v,3e
5 Q1
5=1- Q2
11=3- Q3
31 and a&o'e Q5
8here 'ariation is more than the a&o'e> the a'erage )*R should &e the
a'erage of test results from at least si samples and not three!
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7&! E..e'$ive BR
8here there is significant difference &et"een the )*Rs of su&grade and em&an/ment soils the
design should &e &ased on effecti'e )*R! The effecti'e )*R of the su&grade can &e determined
from igure 1l! or other compacted thic/ness of su&grade> ref 4 ma( &e consulted for
guidance! included in IIT,0%+ )D!
7&+& De$er%in$ion o. resi,ien$ %od3,3s
The &eha'iour of the su&grade under d(namic load of traffic is essentiall( elastic
&ecause of "hich the pa'ement &eha'es in a resilient manner under the transient
traffic loading! The measure of resilient &eha'iour is resilient modulus! Resilient
&eha'iour is important for the performance of the pa'ement! This can &e determined
in the la&orator( &( conducting tests as per procedure specified in 00S;T< T 3-=
$$2--3! Since the repetiti'e triaial testing facilit( is not "idel( a'aila&le and is
epensi'e> it is also possi&le to determine the Resilient Modulus from a )*R
'alues and & alling 8eight Deflectometer 8D test results using generall(
accepta&le correlations "hich are as follo"s
a )*R The relation &et"een resilient modulus and the +ffecti'e )*R is gi'en as
19
CBR below 500mm
of compacted
subgrade
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MRM,a 1-)*R for )*R K 5 and e7ual to J
1!6)*R-!64 for )*R L 5
MR Resilient modulus of su&grade soil!
The )*R of the su&gradeshould &e determined as per IS 22- ,art 16 23 at the
most critical moisture conditions li/el( to occur at site !The test must al"a(s &e performed
on remoulded samples of soils in the la&orator(!The pa'ement thic/ness should &e &ased
on 4=da( soa/ed )*R 'alue of the soil> remoulded at placement densit( and moisture
content ascertained from the field compactioncur'e!
8here'er possi&le the test specimens should &e prepared &( Static )ompaction!
0lternati'el( d(namic compaction ma( also &e used! *oth procedures are descri&ed
in &rief in 0nneure=4!
9& PRINIPLES OF PAVEMENT DESIGN
(Users of these guidelines are advised to read this section in conjunction with Annex I for a
better appreciation of the context and the requireents of !aveent Design"
20
(8
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6!1 0 flei&le pa'ement is modeled as an elastic multila(er structure> Stresses and
strains at critical locations igure 2 are computed using a linear la(ered elastic
model! The Stress anal(sis soft"are IIT,0%+> has &een used for the computation of
stresses and strains in flei&le pa'ements! Tensile strain> t> at the &ottom of the &ituminous
la(er and the 'ertical su&grade strain> '>on the top of the su&grade are con'entionall(
considered as critical parameters for pa'ement design to limit crac/ing and rutting in
the &ituminous and non=&ituminous la(ers respecti'el(! The computation also indicates
that tensile strain near the surface close to edge of a "heel can &e sufficientl( large to
initiate longitudinal surface crac/ing much &efore the crac/ing of the &ottom la(er if the
mi tensile strength is not ade7uate at higher temperatures!
#$% Fatigue in botto la&er of bituinous paveent and fatigue life
6!2!1 8ith e'er( load repetition> the tensile strain de'eloped at the &ottom of the &ituminous
la(er de'elops micro crac/s> "hich goes on "idening and epanding till the load repetitions are
large enough for the &ottom of the &ituminous la(er to crac/> the crac/s to propagate to the
surface> and co'er an area of the surface that is unaccepta&le from the point of 'ie" of
ser'icea&ilit( of the pa'ement! The phenomenon is called fatigue or fracture of the &ituminous
la(er and the num&er of load repetitions in terms of standard ales that cause fatigue denotes the
21
!at"gue res"sta#t m"$
Rut res"sta#t m"$
%ra#ular la&er
t
v
igure 2Different la(ers of a flei&le pa'ement
'ubgrade
B"tum"#ous
surfac"#g
reated or u#treated
)ual w*eel
+t+t e#s"le stra"#
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fatigue life of the pa'ement! In these guidelines> crac/ing in 2-E area has &een considered to
correspond to fatigue life!
#$%$% Fatigue 'odel( atigue model has &een cali&rated in the R=56 studies using the
pa'ement performance data collected during the R=6 and R=1$ studies! T"o fatigue e7uations
"ere fitted> one in "hich the computed strains in #-E of the actual data in the scatter plot "ere
higher than the limiting strains predicted &( the model and termed as #-E relia&ilit( le'el in
these guidelines and the other corresponding to $-E relia&ilit( le'el! The t"o e7uations are
gi'en &elo"
N. ; !&!# < #"8"- 2 =#6>$?
+&@ < =#6MR?"&@7- 88===
$
N.;"#$?
+&@ the fatigue e7uation corresponds to the one "ith $-E
relia&ilit( le'el! The recommendation in these guidelines is to target these 'alues of
&itumen and air 'oids for a fatigue resistant mi!
#$) *utting in !aveent
6!3!1 Rutting is permanent deformation in pa'ement usuall( occurring longitudinall(
along the "heel path! The rutting ma( &e caused either &( deformation in the su&grade>
"hich "ould cause all o'erl(ing la(ers also to deform and ta/e a deformed shape> or in
the &ituminous la(ers onl( due to secondar( compaction of the &ituminous mies under
traffic load! +cessi'e rutting greatl( reduces the ser'icea&ilit( of the pa'ement and it has
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to &e limited to a certain reasona&le 'alue! In these guidelines the limiting rutting is
recommended as 2- mm!
#$)$% *utting odel9i/e fatigue model> rutting model has also &een cali&rated in the R=56
studies using the pa'ement performance data collected during the R=6 and R=1$ studies at #-E
and $-E relia&ilit( le'els! The t"o e7uations are gi'en &elo"
C 4!1656 1-=-#1'N4!533 ============== 11
C 1!41 1-=# 1'N4!533 ============== 12
0s can &e seen> the model considers the 'ertical strain in su&grade as the onl( 'aria&le! 8hile
the pa'ement founded on a strong su&grade ma(> as a la(ered s(stem> &e resistant to rutting> the
other cause of the rutting> the secondar( compaction of the &ituminous la(ers> also needs to &e
addressed! The recommendation in these guidelines is to pro'ide rut resistant &ituminous mies
using higher 'iscosit( grade &itumen or modified &itumen!
#$+ ,op down cracking in bituinous la&er( 8hile fatigue crac/ing is a F&ottom up@
phenomenon> Ftop do"n@ crac/ing has also &een o&ser'ed on high 'olume roads in the countr(>
&ecause of ecessi'e tensile stresses de'eloping at the top surface due to hea'( ale loads! These
guidelines recommend a rut as "ell as fatigue resistant mi to pre'ent top do"n crac/ing!
#$- .eentitious sub base and base(
#$-$/ )ementatious materials crac/ due to shrin/age and temperature e'en "ithout pa'ement
&eing loaded! 8hile ma/ing a ?udgment on the strength 'alues for design> the reduction in
strength due to the crac/ed condition of these la(ers need to &e full( recogni:ed! The +lastic
Modulus +> Resilient Modulus MR> .nconfined )ompressi'e Strength> and fleural strength
'alues recommended for designs are much less than their respecti'e la&orator( 'alues! The
etent of reductions proposed has &een generall( in agreement "ith practices follo"ed in the
national standards of other countries li/e 0ustralia> South 0frica> M+,DG of the .S0> etc!
There are 'er( limited data in the countr( on the field performance of such t(pe of construction
to understand and model their performance in the field! Therefore> the ne" pa'ements
constructed "ith these materials need to &e closel( monitored! These guidelines strongl(
recommend construction "ith cementitious materials in the interest of sa'ing the en'ironment
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and using the local and marginal materials after sta&ili:ation! The a&sence of field performance
data need not &e considered a handicap &ecause the de'elopments "orld o'er seems to ha'e
ta/en place "ithout field 'alidation! or eample> M,+DG recogni:es that Fthe fatigue crac/ing
prediction e7uation for semi=rigid pa'ement "as not cali&rated@!
#$-$% Fatigue cracking in ceentitious la&ers( In these guidelines> the treatment of fatigue
crac/ing of cementitious is recommended at t"o le'els! irst> an o'erall fatigue life of the la(ers
in terms of standard ales is e'aluated! 0t the second le'el> the cumulati'e fatigue damage of
indi'idual ales is calculated &ased on a model "hich uses Fstress ratio@ i!e! the ratio of actual
stresses de'eloped due to a class of "heel load and the fleural strength of the material as the
parameter! The computation of stresses due to the indi'idual "heel load is done &( the IIT,0%+
program! The program also calculates the cumulati'e fatigue of each class of "heel loads and
aggregates o'er the entire ale load spectrum! The design re7uirement is that the cumulati'e
damage of all "heel loads should &e less than 1! If it is greater than 1> the section has to &e
changed and iteration done again! The first model is ta/en from the 0ustralian eperience> "hile
the second one is suggested in M+,DG! The t"o fatigue e7uations are gi'en &elo"
0!
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*! )umulati'e atigue Damage
9og Cf ===== 14
8here>
Vt tensile stress under )ementitious &ase la(er>
MR 2# da( leural strength of the )ementitious &ase!
9& PRINIPLES OF PAVEMENT DESIGN
(Users of these guidelines are advised to read this section in conjunction with Annex I for a
better appreciation of the context and the requireents of !aveent Design"
6!1 0 flei&le pa'ement is modeled as an elastic multila(er structure> Stresses and
strains at critical locations igure 2 are computed using a linear la(ered elastic
model! The Stress anal(sis soft"are IIT,0%+ has &een used for the computation of stresses
and strains in flei&le pa'ements!Tensile strain> t> at the &ottom of the &ituminous la(er and
the 'ertical su&grade strain> '>on the top of the su&grade are con'entionall( considered as
critical parameters for pa'ement design to limit crac/ing and rutting in the &ituminous
and non=&ituminous la(ers respecti'el(! The computation also indicates that tensile
strain near the surface close to edge of a "heel can &e sufficientl( large to initiate
longitudinal surface crac/ing much &efore the crac/ing of the &ottom la(er if the mi
tensile strength is not ade7uate at higher temperatures!
25
!at"gue res"sta#t m"$
Rut res"sta#t m"$
%ra#ular la&er
t
v
igure 2Different la(ers of a flei&le pa'ement
'ubgrade
B"tum"#ous
surfac"#g
reated or u#treated
)ual w*eel
+t+t e#s"le stra"#
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6.2 Fatigue in bottom layer of bituminous pavement and fatigue life5
6!2!1 8ith e'er( load repetition> the tensile strain de'eloped at the &ottom of the &ituminous
la(er de'elops micro crac/s> "hich goes on "idening and epanding till the load repetitions are
large enough for the &ottom of the &ituminous la(er to crac/> the crac/s to propagate to the
surface> and co'er an area of the surface that is unaccepta&le from the point of 'ie" of
ser'icea&ilit( of the pa'ement! The phenomenon is called fatigue or fracture of the &ituminous
la(er and the num&er of load repetitions in terms of standard ales that cause fatigue denotes the
fatigue life of the pa'ement! In these guidelines> crac/ing in 2-E area has &een considered to
correspond to fatigue life!
#$%$% Fatigue 'odel( atigue model has &een cali&rated in the R=56 studies using the
pa'ement performance data collected during the R=6 and R=1$ studies! T"o fatigue e7uations
"ere fitted> one in "hich the computed strains in #-E of the actual data in the scatter plot "ere
higher than the limiting strains predicted &( the model and termed as #-E relia&ilit( le'el in
these guidelines and the other corresponding to $-E relia&ilit( le'el! The t"o e7uations are
gi'en &elo"
Cf 2!21 1-=-4 1tN
3!#$ 1MRN-!#54 ===== $
Cf -!11 1-=-4 1tN
3!#$ 1MRN-!#54 1-
8here> Cf fatigue life> t Maimum Tensile strain at the &ottom of the
&ituminous la(er> MR resilientmodulus of the &ituminous la(er!
Man( fatigue models e!g! M+,DG> Shell> etc include an additional factor F)@ in the
e7uation to ta/e into account the effect of 'olume of &itumen and air 'oids in the
&ituminous mi! 0n anal(sis sho"s that if &itumen content is increased &( -!5 to -!6 E
and air 'oids /ept at 3E le'el> the fatigue e7uation corresponds to the one "ith $-Erelia&ilit( le'el! The recommendation in these guidelines is to target these 'alues of
&itumen and air 'oids for a fatigue resistant mi!
#$) *utting in !aveent
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6!3!1 Rutting is permanent deformation in pa'ement usuall( occuring longitudinall(
along the "heel path! The rutting ma( &e caused either &( deformation in the su&grade>
"hich "ould cause all o'erl(ing la(ers also to deform and ta/e a deformed shape> or in
the &ituminous la(ers onl( due to secondar( compaction of the &ituminous mies under
traffic load! +cessi'e rutting greatl( reduces the ser'icea&ilit( of the pa'ement and it has
to &e limited to a certain reasona&le 'alue! In these guidelines the limiting rutting is
recommended as 2- mm!
#$)$% *utting odel9i/e fatigue model> rutting model has also &een cali&rated in the R=56
studies using the pa'ement performance data collected during the R=6 and R=1$ studies at #-E
and $-E relia&ilit( le'els! The t"o e7uations are gi'en &elo"
C 4!1656 1-=-#1'N4!533 ============== 11
C 1!41 1-=# 1'N4!533 ============== 12
0s can &e seen> the model considers the 'ertical strain in su&grade as the onl( 'aria&le! 8hile
the pa'ement founded on a strong su&grade ma(> as a la(ered s(stem> &e resistant to rutting> the
other cause of the rutting> the secondar( compaction of the &ituminous la(ers> also needs to &e
addressed! The recommendation in these guidelines is to pro'ide rut resistant &ituminous mies
using higher 'iscosit( grade &itumen or modified &itumen!
#$+ ,op down cracking in bituinous la&er( 8hile fatigue crac/ing is a F&ottom up@
phenomenon> Ftop do"n@ crac/ing has also &een o&ser'ed on high 'olume roads in the countr(>
&ecause of ecessi'e tensile stresses de'eloping at the top surface due to hea'( ale loads! These
guidelines recommend a rut as "ell as fatigue resistant mi to pre'ent top do"n crac/ing!
#$- .eentitious sub base and base(
#$-$/ )ementatious materials crac/ due to shrin/age and temperature e'en "ithout pa'ement
&eing loaded! 8hile ma/ing a ?udgment on the strength 'alues for design> the reduction in
strength due to the crac/ed condition of these la(ers need to &e full( recogni:ed! The +lastic
Modulus +> Resilient Modulus MR> .nconfined )ompressi'e Strength> and fleural strength
'alues recommended for design is much less than their respecti'e la&orator( 'alues! The etent
of reductions proposed has &een generall( in agreement "ith practices follo"ed in the national
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standards of other countries li/e 0ustralia> South 0frica> M+,DG of the .S0> etc! There are
'er( limited data in the countr( on the field performance of such t(pe of construction to
understand and model their performance in the field! Therefore> the ne" pa'ements constructed
"ith these materials need to &e closel( monitored! These guidelines strongl( recommend
construction "ith cementitious materials in the interest of sa'ing the en'ironment and using the
local and marginal materials after sta&ili:ation! The a&sence of field performance data need not
&e considered a handicap &ecause the de'elopments "orld o'er seems to ha'e ta/en place
"ithout field 'alidation! or eample> M,+DG recogni:es that Fthe fatigue crac/ing prediction
e7uation for semi=rigid pa'ement "as not cali&rated@!
#$-$% Fatigue cracking in ceentitious la&ers( In these guidelines> the treatment of fatigue
crac/ing of cementitious is recommended at t"o le'els! irst> an o'erall fatigue life of the la(ers
in terms of standard ales is e'aluated! 0t the second le'el> the cumulati'e fatigue damage of
indi'idual ales is calculated &ased on a model "hich uses Fstress ratio@ i!e! the ratio of actual
stresses de'eloped due to a class of "heel load and the fleural strength of the material as the
parameter! The computation of stresses due to the indi'idual "heel load is done &( the IIT,0%+
program! The program also calculates the cumulati'e fatigue of each class of "heel loads and
aggregates o'er the entire ale load spectrum! The design re7uirement is that the cumulati'e
damage of all "heel loads should &e less than 1! If it is greater than 1> the section has to &e
changed and iteration done again! The first model is ta/en from the 0ustralian eperience> "hile
the second one is suggested in M+,DG! The t"o fatigue e7uations are gi'en &elo"
0!
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C atigue life of the )ementitious material!
+ +lastic modulus of )ementitious material!
U tensile strain in the )ementitious la(er> microstrain
*! )umulati'e atigue Damage
9og Cf ===== 14
8here>
Vt tensile stress under )ementitious &ase la(er>
MR 2# da( leural strength of the )ementitious &ase!
! PAVEMENT OMPOSITIONS
Gener,
0 flei&le pa'ement co'ered in these guidelines consists of different la(ers as sho"n in igure 2!
The su&&ase and the &ase la(er can &e un&ound e!g! granular or &ound or cementitious e!g!
cement or lime in com&ination "ith fl(ash! In case of pa'ements "ith cementitious &ase> a
crac/ relief la(er needs to &e mandatoril( pro'ided &et"een the &ituminous surfacing and the
29
!"gure 2 )"ffere#t la&ers of a b"tum"#ous
pa,eme#t
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cementitious &ase to dela( the reflection crac/ in the &ituminous course! This ma( consist of
crushed aggregates of thic/ness 1-- mm conforming to 8MM specification as per clause 4-6 of
M should meet these functional re7uirements!
&! S300se ,4er
&! Un0o3nd S300se ,4er
!2!1!1 Su&&ase materials ma( consist of natural sand> moorum> gra'el> laterite> /an/ar>
&ric/ metal> crushed stone> crushed slag> and Reclaimed crushed
concreteReclaimed asphalt pa'ement or com&inations thereof meeting the
prescri&ed grading and ph(sical re7uirements! 8hen the su&&asematerial consists of
com&ination of materials> miing should &e done mechanicall( either using a suita&le
mier or adopting mi=in=place method! The su&&ase should ha'e sufficient strength and
thic/ness to ser'e the construction traffic!
!2!1!2 Specifications of granular su&&ase GS* materials conforming to M
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material should &e strictl( enforced in order to meet strength> filter and drainage
re7uirements of the granular su&&ase la(er! 8hen coarse graded su&&ase is used as a
drainage la(er> 9os 0ngeles a&rasion 'alue should &e less than 4- so that there is no
ecessi'e crushing during the rolling and the permea&ilit( is retained!
!2!1!3 The su&&ase should &e composed of t"o la(ers> the lo"er la(er forms the
separationfilter la(er to pre'ent intrusion of su&grade soil into the pa'ement and the upper
GS* forms the drainage la(er to drain a"a( an( "ater that ma( enter through surface
crac/s! The drainage la(er should &e tested for permea&ilit( and gradation ma( &e altered
to ensure the re7uired permea&ilit(! ilter and drainage la(ers can &e designed as per IR)
S, 42=1$$4 2- and IR) S, 52=1$$$!
!2!1!4 Strength parameter The rele'ant strength parameter for granular su& &ase is
Resilient modulus MR> "hich is gi'en &( the follo"ing e7uation
MRgs& -!2h-!45 MRWsu&grade J! 15
8here hthic/ness of su&&ase la(er in mm
MR'alue of the su&&ase is dependent upon the MR'alue of the su&grade since "ea/er
su&grade does not permit higher modulus of the upper la(er &ecause of deformation under
loads!
&!&! Bo3nd S300se L4er
!2!2!1 The material for &ound su& &ase ma( consist of soil or aggregate sta&ili:ed "ith
cementitious material such as cement> lime=fl( ash> commerciall( a'aila&le sta&ili:ers etc!
The drainage la(er of the su&&ase ma( consist of coarse graded aggregates &ound "ith
a&out 2E to 3E cement or 2E to 3E &itumen emulsion to pre'ent distortion in its profile
due to construction traffic "hile retaining the permea&ilit(! In case soil modified "ith
cementatious material is used as a su&&ase and granular material is not easil( a'aila&le>
geocomposites can &e used as drainage and filter la(er!
!2!2!2 Strength ,arameter The rele'ant strength parameter for &ound su& &ases is the
+lastic Modulus +> "hich can &e determined from the unconfined compressi'e strength of
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the material! In case of &ound GS*> the la&orator( &ased + 'alue is gi'en &( the follo"ing
e7uations
+cgs& 1--- .)S J! 16
&itumen emulsion
treated aggregates and cementitious treated soilaggregates! Rele'ant specifications of
IR)M the
composite resilient modulus of the granular su&&ase and the &ase is gi'en as
MRWgranular -!2 h-!45MRWsu&grade J 1
8here hthic/ness of granular su&&ase and &ase> mm
&+&! Bo3nd Bse L4er
&+&! *ound &ase la(ers ma( consist aggregates or soil sta&ili:ed "ith cementitious
sta&ili:ers li/e cement> lime=fl(ash=cement or other chemical sta&ili:ers to gi'e a
minimum da( strength of 4!5 to M,a IR) S,=#$=2-1- 1! Though the initial
modulus of the )ementitious &ases ma( &e in the range 1---- to 15--- M,a> there is
reduction of modulus 'alues up to fift( percent of the initial modulus due to shrin/age and
the construction traffic 4#> 4$B and the effecti'e elastic modulus of the )ementitious &ase
"ill &e much less> and ultimatel( not more than that gi'en &( the e7uation 1> as if the
entire &ase has con'erted to granular la(er!
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!3!2!2 Strength parameter leural strength is re7uired for carr(ing out the fatigue anal(sis as
per fatigue e7uation! M+,DG suggests for chemicall( sta&ili:ed &ases the modulus of rupture
can &e ta/en as 2-E of the 2# da( unconfined compressi'e strength! The same is recommended
in these guidelines! or the initial design> the follo"ing 'alues of modulus of rupture are
recommended
)ementitious sta&ili:ed aggregates 1!4 M,a
9ime=cementitious=fl(ash 1!-5 M,a
!3!2!3Dura&ilit( criteria The minimum cementitious content in the cementitious &ase
la(er should &e such that in a "etting and dr(ing test *IS 4332 ,art I% = 1$6# $> the
loss of "eight of cementitious treated aggregates does not eceed 14E after 12 c(cles of
"etting and dr(ing! In cold and sno" &ound regions li/e 0runachal ,radesh> Xammu
Aashmir> 9ada/h> ;imachal ,radesh etc! dura&ilit( should &e determined &( free:ing and
tha"ing test and the loss of "eight should &e less than 14E after 12 c(cles *IS 4332
,art I% Y 1$6# $! )ementitious la(er meeting the strength re7uirements of IR)S,#$=
2-1- is found to meet the criteria of dura&ilit( re7uirement #!
&+&!&- )rac/ relief la(er 0 S0MI la(er using modified &itumen pro'ided o'er the
cementitious la(er dela(s the crac/s propagating into the &ituminous la(er! 0 crac/ relief
la(er of "et mi macadam of thic/ness 1--mm sand"iched &et"een the &ituminous la(er
and treated la(er is much more effecti'e in arresting the propagation of crac/s from the
)ementitious &ase to the &ituminous la(er #>11>4#>4$! The aggregate la(er &ecomes
stiffer under hea'ier loads &ecause of high confining pressure! The granular la(er ma( &e
treated "ith 1 to 2E &itumen emulsion of grade RS> to a'oid reshaping &ecause of sho'ing
and deformation in the un&ound la(er caused &( the construction traffic!
!3!2!5 Strength of crac/ relief la(er The Resilient Modulus of the granular la(er pro'ided&et"een the )ementitious and &ituminous la(ers on the top is dependent upon the confinement
pressure under "heel load 3> #> 14> 4# and 4$! The modulus ma( 'ar( from 3-- to 1--- M,a
and a t(pical 'alue of 45- M,a #> 4# and4$ ma( &e used for the aggregate la(er sand"iched
&et"een a &ituminous surface and the )ementitious &ase for the anal(sis of pa'ements! Strong
support from )ementitious &ase> results in higher modulus than "hat is gi'en &( +7uation 3! 0
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Mies "ith %G4- &itumen results in much higher moduli and studies indicate that modulus
'alues "ith %G4- &itumen and those "ith modified &itumen are compara&le at 6--)!
)ommerciall( a'aila&le modified &inders ha'e different t(pes of pol(mersB it is recommended
that the( should &e tested for their moduli and fatigue 'alues depending upon the structural
re7uirement!
!4!2 atigue &eha'ior of mies "ith modified &itumen is higher as compared to mies "ith
normal &itumen 1->25>2$ and 52! +periments ha'e sho"n that the &inder content is increased
&( -!5 to -!6 percent o'er and a&o'e the optimum to o&tain an air 'oid of 3E> the fatigue li'es
are increased &( more than t"ice for normal as "ell as modified &inders 1->15> 25> 2$> and 52!
;o"e'er since the 'oids are 'er( critical for &leeding if the &itumen grade is not appropriate
then "ith ecess &itumen and critical air 'oid ratio the performance "ill &e ad'ersel( affected!
or pa'ement design considerations using properties of &ituminous mies for optimum design
and selection of &inder is descri&ed in the net section!
T0,e # Resi,ien$ Mod3,3s o. Bi$3%ino3s %i2esC MP
Mi2 $4e
Te%er$3re"
2- 25 3- 35 4-
*) and D*M for %G1- &itumen 23-- 2--- 145- 1--- #--
*) and D*M for %G3- &itumen 35-- 3--- 25-- 1-- 125-
*) and D*M for %G4- &itumen 6--- 5--- 4--- 3--- 2---
*) and D*M for Modified *itumen IR) S,
53=2-1-5-- 3#-- 24-- 165- 13--
*M "ith %G 1- &itumen 5-- M,a at 35-)
*M "ith %G 3- &itumen -- M,a at 35-)
8MMR0, treated "ith 3E &itumen
emulsionfoamed &itumen 2E residual
&itumen and 1E cementatious material!
6-- M,a at 35-) 'aries from -- to 12--M,a
for "ater saturated samples!
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The ,oissonZs ratio of &ituminous la(er ma( &e ta/en as -!5- for pa'ement
temperatures of 35[) and higher! or temperatures from 2-[) to 3-[)> a 'alue of
-!35 ma( &eadopted! atigue e7uation at an( pa'ement temperature from 2-[) to 4-[)
can &e e'aluated &( su&stituting the appropriate 'alue of the resilient modulus of the
&ituminous mi! )atalogue of designs has &een "or/ed out for a temperature of
35[)!
#! Pere$3, Pve%en$5
The pa'ements "hich ha'e theoreticall( life of 5- (ears or longer are termed as
perpetual pa'ements! If the tensile strain caused &( the traffic in the &ituminous la(er is
less than - micro strains> the endurance limit of the material> the &ituminous la(er
ne'er crac/s 0sphalt Institute> MS=4> thedition 2--! Similarl( if 'ertical su&grade
strain is less than 2-- micro strains rutting in su&grade "ill ne'er happen! Design of
such a pa'ement is illustrated in the guideline!
& Pve%en$ Desi*n hr$s
The Illustrati'e pa'ement design catalogues are gi'en for the follo"ing cases
1! Pve%en$ Thi'ness Desi*n hr$s .or $r..i' 3$o # %s /i$h *ituminous pa'ements
"ith Granular *ase and Granular Su&&ase!)l $!1 ,late 1 to #
2! ,a'ement Thic/ness Design )harts for 2msa and a&o'e "ith *ituminous pa'ements "ith
Granular *ase and Granular Su&&ase! )l $!2 ,late $ to 12
3! 3! *ituminous pa'ements "ith cementitious &ase and cementitious su&&ase ha'ing
1--mm of aggregate interla(er for crac/ relief! .pper 1--mm of the cementitious
su&&ase is the drainage la(er!)l $!3 ,late 13 to 16
4! 4! *ituminous pa'ements "ith cementitious &aseT and su&&ase "ith S0MI at the interface
of &ase and the &ituminous la(er! .pper 1--mm of the cementitious su&&ase is drainage
la(er )l $!4 ,late 13 to 16
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5! 5*ituminous pa'ements "ith foamed &itumen&itumen emulsion treated R0, aggregates
o'er 25-mm )ementitious su&&ase top 1--mm is the drainage la(er! )l $!5 ,late 1 to
2-
6! 6! *ituminous pa'ements "ith cementatious &ase and granular su&&ase "ith crac/ relief
la(er of aggregate la(er a&o'e the cementatious &ase! )l $!6 ,late 21 to 24
There can &e man( more com&inations depending on the local conditions! Designers
can select different materials and anal(:e them using the &asic approach gi'en in the
guidelines!
0 long life pa'ement ha'ing design traffic of 3--msa is gi'en in the 0nneure 2!
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Pve%en$ Thi'ness Desi*n hr$s .or $r..i' 3$o # %s
(A) Bi$3%ino3s ve%en$s /i$h Grn3,r Bse nd Grn3,r S300se&
Tr..i'
(Ms)
BR
To$,
Thi'ness
(%%)
Pve%en$ o%osi$ion
Bi$3%ino3s S3r.'in* Grn3,r
Bse
(%%)
Grn3,r
S30Bse
(%%)
erin*
o3rse
(%%)
Binder
o3rse
(%%)
# + 77" !" P !!7 -+7
# - -@" !" P !!7 !77
# 7 -+" !" P !!7 !"7
# 9 +" !" P !!7 #97
# +7 !" P !!7 #7"
# @ +7 !"P !!7 #7"
# #" +7 !" P !!7 #7"
&! Pve%en$ Thi'ness Desi*n hr$s .or !%s nd 0ove
(A)Bi$3%ino3s ve%en$s /i$h Grn3,r Bse nd Grn3,r S300se&
For $r..i'+"%sC VG-" 0i$3%en is re'o%%ended& Thi'ness o. DBM .or +#87" Ms is
,o/er or e:3, $hn $h$ o. $he rn*e !#8+"%s d3e $o s$i..er 0i$3%en& Lo/er DBM hs ir
void o. + .$er ro,,in* (Bi$3%en 'on$en$ is "&7 $o "&9 hi*her $hn $he o$i%3%)& For
$r..i' 3$o 7%s ,soC i%ervio3s ,4ers o. SDB nd DBM is re'o%%ended& Lo',
e2erien'e is $he 0es$ *3ide& GSB 'onsis$s o. .i,$er nd drin*e ,4ers&
PAVEMENT DESIGN ATALOGUE
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PLATE #8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE !8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
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PLATE +8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE -8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
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PLATE 78 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE 98 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
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PLATE 8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE @8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
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&+ Bi$3%ino3s ve%en$s /i$h 'e%en$i$io3s 0se nd 'e%en$i$io3s s300se hvin*
#""%% o. **re*$e in$er,4er .or 'r' re,ie.& Uer #""%% o. $he 'e%en$i$io3s
s300se is $he drin*e ,4er&
For $r..i'+"%sC VG-" 0i$3%en is 3sed .or reven$in* r3$$in*& DBM hs ir void o. +
.$er ro,,in* (Bi$3%en 'on$en$ is "&7 $o "&9 hi*her $hn $he o$i%3%)& r'in* o.
e%en$i$io3s 0se is $en s $he ,i.e o. ve%en$&
PAVEMENT DESIGN ATALOGUE
PLATE 8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
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PAVEMENT DESIGN ATALOGUE
PLATE #"8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE ##8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
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PAVEMENT DESIGN ATALOGUE
PLATE #!8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
&- Bi$3%ino3s ve%en$s /i$h 'e%en$i$io3s 0se(T) nd s300se /i$h SAMI $ $he
in$er.'e o. 0se nd $he 0i$3%ino3s ,4er& Uer #""%% o. $he 'e%en$i$io3s s300se is
drin*e ,4er
For $r..i'+"%sC VG-" 0i$3%en is 3sed& DBM hs ir void o. + .$er ro,,in* (Bi$3%en
'on$en$ is "&7 $o "&9 hi*her $hn $he o$i%3%)& r'in* o. e%en$i$io3s 0se is $en
s $he ,i.e o. ve%en$&
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PAVEMENT DESIGN ATALOGUE
PLATE #+8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
No$e5 T Bse sho3,d red s E;7""" M
PAVEMENT DESIGN ATALOGUE
PLATE #-8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
No$e5 T Bse sho3,d red s E;7""" M
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PAVEMENT DESIGN ATALOGUE
PLATE #78 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
No$e5 T Bse sho3,d red s E;7""" M
PAVEMENT DESIGN ATALOGUE
PLATE #98 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
No$e5 T Bse sho3,d red s E;7""" M
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&7 Bi$3%ino3s ve%en$s /i$h .o%ed 0i$3%en60i$3%en e%3,sion $re$ed RAP6
**re*$es over !7"%% e%en$i$io3s s300se ($o #""%% is $he drin*e ,4er)&
VG-" is 3sed .or $r..i'+"%s& DBM hs ir void o. + .$er ro,,in* (Bi$3%en 'on$en$ is
"&7 $o "&9 hi*her $hn $he o$i%3%)& F$i*3e .i,3re o. $he 0i$3%ino3s ,4er is $he end
o. ve%en$ ,i.e&
PAVEMENT DESIGN ATALOGUE
PLATE # 8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
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PAVEMENT DESIGN ATALOGUE
PLATE #@ 8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE #8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
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PAVEMENT DESIGN ATALOGUE
PLATE !"8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
&9 (E&) Bi$3%ino3s ve%en$s /i$h 'e%en$$io3s 0se nd *rn3,r s300se /i$h 'r'
re,ie. ,4er o. **re*$e ,4er 0ove $he 'e%en$$io3s 0se&
In a t"o la(er construction of &ituminous la(er> the &ottom la(er should ha'e an air 'oid of 5E
&( incorporating additional &itumen of -!5 to -!6E !The crac/ la(er should meet the
specifications of 8et Mi Macadam and ma( contain a&out 1 to 2E &itumen emulsion so that its
surface is not distur&ed &( construction traffic! +mulsion can &e mied "ith "ater to ma/e the
fluid e7ual to optimum "ater content and added to the 8MM during the processing! The
granular should consist of drainage as "ell as filterseparation la(er! 0 relia&ilit( of #-E is used
for traffic up to 3-msa and $-E for trafficL3-msa!%G3- &itumen is recommended for traffic up
to 3-msa and %G4- for trafficL3-msa!
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PAVEMENT DESIGN ATALOGUE
PLATE !#8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE !!8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
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PAVEMENT DESIGN ATALOGUE
PLATE !+8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
PAVEMENT DESIGN ATALOGUE
PLATE !-8 REOMMENDED DESIGNS FOR TRAFFI RANGE !8#7" %s
#"& In$ern, drin*e in Pve%en$
#"!1! The performance of a pa'ement can &e seriousl( affected if ade7uate drainage
measures to pre'ent accumulation of moisture in the pa'ement structure are not ta/en!
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Some of the measures to guard against poor drainage conditions are maintenance of
trans'erse section in good shape to reasona&le crossfall so as to facilitate 7uic/ run=off
of surface "ater and pro'ision of appropriate surface and su&=surface drains "here
necessar(! Drainage measures are especiall( important "hen the road is in cutting or
&uilt on lo" permea&ilit( soil or situated in hea'( rainfallsno" fall area!
1-!2! not &e
less than 1!-m! In "ater logged areas> "here the su&grade is "ithin the :one of
capillar( saturation> consideration should &e gi'en to the installation of suita&le
capillar( cut=off as per IR) 34 at appropriate le'el underneath the pa'ement!
1-!3! 8hen the traditional granular construction is pro'ided on a relati'el( lo"
permea&ilit( su&grade> the granular su&&ase should &e etended o'er the entire
formation "idth in order to drain the pa'ement structural section! )are should &e
eercised to ensure that its eposed ends do not get co'ered &( the em&an/ment soil!
The trench t(pe section should not &e adopted in an( case as it "ould lead to the
entrapment of "ater in the pa'ement structure!
1-!4 If the granular su&&ase is of softer 'ariet( "hich ma( undergo crushing during
rolling leading to denser gradation and lo" permea&ilit(> the top 1-- to 15- mm
thic/ness should &e su&stituted &( an open graded crushed stone la(er of 9os 0ngeles
a&rasion 'alue not eceeding 4- to ensureproper drainage!
The filter la(er must ha'e enough permea&ilit( to pre'ent de'elopment of undesira&le pore "ater
pressure and it should drain a"a( an( free "ater that enters into it al&eit at much lo"er rate as
compared to the drainage la(er
The filterseparation la(er should satisf( the follo"ing criteria
To pre'ent entr( of soil particles into the drainage la(er
53
515
15
subgradeofD
la&erfilterofD
5#5
15
subgradeofD
la&erfilterofD
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Outlet
pipeOpen graded base
Sub base
#"& Drin*e re:3ire%en$5 ;ea'( ale loads commonl( pl( on ma?or roads in India and
therefore> it should &e ensured that the un&ound la(ers do not undergo unaccepta&le permanent
deformation under repeated loading! The su&grade and the granular la(ers "ith entrapped "ater
"ould &e su&?ected to large permanent deformation under hea'( loads causing erosion of the
un&ound la(er! It is necessar( to pro'ide a drainage la(er to drain a"a( the "ater entering into
the pa'ement! The coarse graded granular su&&ase 46 "ould ha'e the necessar( permea&ilit( of
3--mda( "ith percent fines passing -!-5mm sie'e less than 2E! 9a&orator( test must &e
conducted for the e'aluation of the permea&ilit( of the drainage la(er! If the surface of
the open graded drainage la(er is li/el( to &e distur&ed &( the construction traffic the la(er ma(
&e treated "ith 2E cement2=2!5E of &ituminous emulsion "ithout an( significant loss of
permea&ilit(! ield test &( Ridge"a( in .S0 indicated that it is the duration of lo" intensit(
sustained rainfall rather than high intensit( rainfall that is critical for infiltration of "ater into the
pa'ement! It "as found that the infiltration rate through the ?ointscrac/s "as -!223 m3da(m
and this 'alue can &e used for design of drainage la(er in the a&sence of field data! The
infiltration rate per unit area 7ican &e epressed as
56
Fig 8 Longitudinal pipe at the edge of the drainage layer with outlet pipe
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7iIc
in "hichIc is the crac/ infiltration rate> is the num&er of longitudinal ?ointscrac/s> is the
"idth of pa'ement su&?ected to infiltration> is the length of the trans'erse crac/s or ?oints> )s
the spacing of trans'erse ?oints and Ap is the rate of infiltration per unit area through uncrac/ed
pa'ement surface> "hich is almost negligi&le for ,))! )edergren recommended design
infiltration rates a&o'e 5-E of the 1hour rainfall of 1 (ear fre7uenc(! The computed 'alue is
found to &e too high and the Ridge"a( method can &e adopted for design of drainage la(er! 0n
eample is gi'en in 0nneure 4!
##& DESIGN IN FROST AFFETED AREAS
11!1! In areas suscepti&le to frost action> the design "ill ha'e to &e related to actual
depth of penetration and se'erit( of the frost! 0t the su&grade le'el> fine grained cla(e(
and silt( soils are more suscepti&le to ice formation> &ut free:ing conditions could
also de'elop "ithin the pa'ement structure if "ater has a chance of ingress from a&o'e!
11!2! &ut this ma( not al"a(s &e economicall(
practica&le! 0s a general rule> it "ould &e inad'isa&le to pro'ide total thic/ness less
than 45- mm e'en "hen the )*R 'alue of the su&grade "arrants a smaller thic/ness! In
addition> the materials used for &uilding up the crust should &e frost resistant!
11!3! 0nother precaution against frost attac/ is that "ater should not &e allo"ed to
collect at the su&grade le'el "hich ma( happen on account of infiltration through the
pa'ement surface or 'erges or due to capillar( rise from a high "ater ta&le!8hereas capillar( rise can &e pre'ented &( su&soil drainage measures and cut=offs>
infiltrating "ater can &e chec/ed onl( &( pro'iding a suita&le "earing surface!
#!& S3%%r4 o. Pve%en$ Desi*n Pro'ed3re&
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The anal(sis and Design of ,a'ement ma( &e carried out &( an( of the
follo"ing approaches
0! In )ase of 'er( lo" traffic in the range of 1 and 2 msa then the charts
pro'ided in para $!2 0 shall &e follo"ed!
*! In case of higher traffic IIT,0% Soft"are ma( &e used! This
Soft"are is included along "ith the ,a'ement Design Guidelines in a
)D!
The necessar( inputs re7uired in this soft"are are
i! Run the IIT,0%!+\+ file
ii! It "ill 1st as/ for the num&er of la(ers of the pa'ement
structure! This is capa&le of handling upto la(ers!
iii! Cet + 'alues of the 'arious la(ers in /gcm2 shall &e pro'ided
as an input
i'! Cet gi'e the Mu or ,oissons ratio of each la(er
'! The thic/ness of each la(er ecluding the su&grade thic/ness
are to &e pro'ided
'i! ,ro'ide "hether anal(sis is for single "heel load or dou&le
"heel load
'ii! The feed the no of computations re7uired
'iii! Then correspondingl( ,ro'ide the 'alues of depth ] in cm and
the corresponding 'alue of r radii
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i! The program "ill run and as output pro'ide the corresponding
stresses and strains! Cet chec/ if the generated strain is less
than the permissi&le strain if not then run the program change
the thic/ness again till the permissi&le strain 'alues are
achie'ed!
)! 0lternatel( use the Design charts pro'ided in the tet of the
Guidelines! The charts can help in finali:ing the design as re7uired!
The design eamples are pro'ided in 0ppendi 2> this "ill help the
field +ngineers to design the pa'ement thic/ness re7uired!
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Anne23re #
The IIT,0%+ soft"are is capa&le of anal(:ing la(er elastic s(stem in "hich all la(ers are
&onded at the interfaces! 8ith minor changes in the soft"are> pa'ement s(stems "ith smooth
interfaces can also &e anal(:ed! %ertical su&grade strain> '> needs to &e /ept &elo" a
certain 'alue for a gi'en traffic to limit rutting in the su&grade and granular la(ers of a "ell
constructed pa'ement! Research findings indicate that the plastic 'ertical strain> p> in
pa'ement materials depends upon the magnitude of elastic 'ertical strain> '> gi'en as
p ' A Cc J!! #
8here p and ' are plastic and elastic strains respecti'el(> C num&er of
repetition of ale loads> A and c are constants
If the computed 'on the su&grade for a gi'en "heel load is lo"> the 'ertical strain in the upper
granular la(ers also is lo"! ;ence limiting the su&grade strain controls the rutting in the su&grade
as "ell as in the granular la(ers! *ituminous la(er must ha'e mi "hich is rut resistant!
The elastic tensile strains> t> at the &ottom and at the top of the &ituminous la(er should not
eceed a certain limit for a gi'en design traffic to control de'elopment of crac/s during the
design period! Surface crac/ ma( de'elop on either side of the "heel path as
sho"n in igure 4! Tensile stains near the edge of the t(res can &e higher than
that at the &ottom and surface crac/s ma( de'elop much earlier than those at
the &ottom particularl( at higher temperatures! Though a num&er of cases of Top
Do"n )rac/ing "ithin a (ear or t"o of opening to traffic has &een found at man( locations 25>
2 and 51 in the *) and the D*M la(ers in India> surface &leeding and rutting 35> 3 and 45
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rather than surface crac/ing has &een 'er( common &ecause of secondar( compaction o"ing to
the softer &itumen for the climate and traffic!
Surface trans'erse surface crac/s ma( also de'elop due to hori:ontal shear stresses applied &(
the dual "heels of hea'( commercial 'ehicles during acceleration and &ra/ing if the mi does
not ha'e enough tensile strength!
The surface crac/s responsi&le for top do"n crac/ing sho"n in igure 4 can &e dela(ed &( using
high 'iscosit( &inder such as %G4- or pol(mer)rum& ru&&er modified &inder &ecause of high
tensile strength in the top la(er of the &ituminous surfacing at higher temperatures! 9o"
temperature trans'erse crac/ing associated "ith stiffer &inders is not a pro&lem in plains of
India! *itumen of lo"er 'iscosit( controls trans'erse surface crac/ing in colder regions as per
international eperience! In the light of the a&o'e> the approach discussed in the follo"ing is
recommended for design of &ituminous pa'ements!
&!&! R3$$in* in s30*rde nd *rn3,r ,4er
9arge amount of field data for rutting in flei&le pa'ements "ere collected and
anal(:ed during se'eral research pro?ects of M
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eperience! Rut resistant mies for high 'olume traffic "ith air temperatures of 4- -) and a&o'e
can &e o&tained &( using high 'iscosit( &inders such as %G4-> ,M*4-> and )RM*6- etc!
9a&orator( rut tests using IITAG, R.T tester on mies "ith %G4- &itumen> ,M* 4- as "ell as
)RM* 6- indicated almost e7ual performance at 5--)! %G3- &itumen ga'e much higher rutting
in the rut tester> a phenomenon o&ser'ed in the field also though it meets the superpa'e
specification re7uirement5> 25 of 1 /,a for Gsin^ at 64-) using D(namic Shear Rheometer!
0nal(sis &( M+,DG model 3 also predicted 5-E rut depth in mies "ith %G4- &itumen as
compared to that "ith %G3- 36! +'en "hen modified &itumen is used in the "earing course>
the rutting ma( occur in the D*M 3 la(er made "ith %G3- ?ust &elo" the "earing course
3! ;ence a higher grade of &inder is recommended for the mi &oth for the *) and the D*M
la(er &elo" the "earing course under hea'( traffic conditions for the maimum air temperatures
of 4-_) and higher> 'er( common on plains of India! Recommendation of IR) 111=2--$ for use
of %G4- &itumen in *) as "ell as D*M la(er ma( &e adopted if the pa'ement carries o'er 2---
commercial 'ehicles per da(! Stone Matri 0sphalt IR) S, $=2--# 1$ is
another "earing course that is /no"n to &e rut as "ell as fatigue resistant!
Marshall Method of mi design is recommended for determination of optimum
&inder content!
&!&- F$i*3e resis$n$ 0i$3%ino3s ,4er
!2!4!1 9a&orator( tests and field performance indicate 3> 1-> 15> 25 and 2
that fatigue life of a &ituminous la(er depends to a great etent on the &itumen
content for a gi'en mi! 0 &ituminous la(er "ith higher modulus de'elops
lo"er tensile strain at the &ottom of the la(er &( a "heel load! To ensure that
the &ottom Dense *ituminous Macadam has a higher fatigue life> it should
contain higher &itumen content! *ut softer grade &itumen such as %G3- ma(
gi'e an unsta&le mi! or a &ituminous la(er thic/ness of 15-mm and higher>
the temperature of the &ottom D*M is significantl( lo"er than the top
&ituminous "earing course and there is little chance of rutting in the &ottom
la(er if the air 'oid is close to 3 percent! ;igher &itumen content in the &ottom
la(er ma/es the mi resistant to stripping and it also pro'ides a strong &arrier
for entr( of moisture in upper &ituminous la(er 1-! )omputations further
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sho"s that the tensile strain in the "earing course near the edge of the t(re can
&e e'en higher3>36>4 than that at the &ottom of &ituminous la(er particularl(
at higher temperatures and therefore> the "earing course also must &e fatigue
resistant in addition to &eing rut resistant! In a t"o la(er &ituminous
construction consisting of *) and D*M> %G4- should &e used for &oth the
la(ers "ith D*M ha'ing -!5E to -!6E higher &itumen content so that the air
'oid is close to 3E! Mies "ith ,ol(mer and )rum& Ru&&er Modified &inders
ha'e fatigue li'es "hich can &e t"o to ten times higher than the normal
mies25>31and 52 depending upon the &inder content and designers can
utili:e this propert( in designing high fatigue life &ituminous pa'ements after
carr(ing out la&orator( tests!
!2!3!3 atigue li'es of a &ituminous miture at a relia&ilit( le'el of #-E
and $-E 33> 4- respecti'el( are gi'en as
Cf 2!21 1-=-4 1tN
3!#$ 1MRN-!#54 ===== 11
Cf -!11 1-=-4 1tN
3!#$ 1MRN-!#54 12
Cf fatigue life> t Maimum Tensile strain at the &ottom of the &ituminous la(er>
MR resilientmodulus of the &ituminous la(er!
+7!11 "as used in IR) 3=2--1!
or high 'olume high"a(s> a relia&ilit( le'el of $-E and higher is used in international
guidelines to a'oid fre7uent maintenance! +7uation 12 is close to the fatigue line of
0.STR
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D*M la(er &ecause of its lo"er modulus! 0sphalt Institute 6> Shell 1$#> Shell ,a'ement
Design Manual=0sphalt ,a'ements and
Cf -!5161 )1-=-4 1tN
3!#$ 1MRN-!#54 13
8here> ) 1-M> 6$!-#4!4 +
=
ba
b
11
1' !! 14
%aair 'oid and %&'olume of &itumen!
Cf fatigue life> `t maimum tensile strain at the &ottom of D*M!
MR Resilient modulus of &ituminous mi!
If %a4!5E and %&11!5E corresponding to &itumen content of approimatel( 4!5E &( "eight of
total mi > +7uation 13 is reduced to +7uation 12 ha'ing a relia&ilit( of $-E!If the constant -!5161
of +7!13 is replaced &( 1!6-4 -!51612!21-!11 the modified e7uation "ill ha'e a relia&ilit( of
#-E! +ffect of &itumen content can thus &e accounted for to determine the fatigue life of a
&ituminous miture!
If -!5E to -!6E additional &itumen is used in a mi to ha'e an air 'oid close to 3E> the
constant in the +7uations 13 can &e e'aluated from +7uation 14!
+7uations 11 and 12 gi'es fatigue li'es for 2-E crac/ed area of the &ituminous la(er at a
relia&ilit( le'el of #- and $-E respecti'el( at the end of the design period! To a'oid
fre7uent maintenance> a relia&ilit( le'el of $-E is recommended for high 'olume roads
ha'ing a design traffic eceeding 3-msa! Since most places on plains of India ha'e
maimum air temperatures e7ual to 4-_) or higher> %G4- &itumen is recommended for
higher traffic and no additional thic/ness of &ituminous la(er than "hat is specified as
per IR) 3=2--1 "ill &e re7uired if the &ottom &ituminous la(er is made fatigue
resistant &( increasing the &inder content &( -!5E to -!6E so that the air 'oid is around
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Anne23re !
ORED EXAMPLES ILLUSTRATING THE DESIGN METHOD
(i) Bi$3%ino3s ve%en$s /i$h 3n$re$ed *rn3,r ,4er
E2%,e 8 ,5Design the pa'ement for construction of a ne" flei&le pa'ement "ith
the follo"ing data
DATA
i our lane di'ided carriage"a(
ii Initial traffic in the (ear of completion of construction 5--- )%da(
Sum of &oth directions
iii Traffic gro"th rate per annum 6!- per cent
i' Design life 2- (ears
' %ehicle damage factor 4!5
*ased on ale load sur'e(
'i )*R of soil &elo" the 5--mm of the su&a
