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A seminar report on

Rigid pavements as alternative specification for

Expressway by

SONI PRAGNESH B

!Roll No ""#

Guide

$iss R N S%&'la

(I)I* ENGINEERING +EPAR,$EN,

* + (O**EGE O- ENGINEERING

AH$E+ABA+ . /01 1"2

$A3 4115

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(ertificate

This is to certify that the seminar entitled “ RIGI+ PA)E$EN,S AS

A*,ERNA,I)E SPE(I-I(A,ION -OR E6PRESS7A3 ” which is submitted

by Soni Pragnes% B Roll No.11 for partial fulfillment of the requirement for the

degree of Master of ngineering !em"## $%i&il' in Transportation engineering

within four walls of * + (ollege of Engineering to Gu(arat )ni&ersity*

+hmedabad is a record of wor, super&ision and guidance of Miss.R. N. !hu,la.

$Guide'

-ate" Miss. R. N. !hu,la.

ecturer*%i&il ngg. -ept.

.-.%ollege of engineering.

+hmedabad / 0 2 213

4aminer" 5rof. 6.M.!hah

7ead of the -epartment

%i&il ngg. -ept..-.%ollege of engineering.

+hmedabad / 0 2 213

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Ac'nowledgement

# ta,e this opportunity to than, Miss.R.N.!hu,la. 9aculty:%i&il ngineering

-epartment* .-.%ollege of ngineering* +hmedabad for organi;ing the concept

of seminar presentation and also for his &aluable guidance and formation of

methodology and compilation of this seminar report.

# would li,e to e4press my deep sense of gratitude towards the faculty members of

%i&il ngineering -epartment and my colleagues for gi&ing the guidance and

support.

May* 822< Soni Pragnes% B

M. . %#=# $TR+N!5>RT+T#>N NGG.'

R> N>" 11

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A8stract

Report focuses on considerations of rigid pa&ements for their requirements of

e4pressway such as traffic safety* tra&el comfort* durability e.t.c.#t contains

precautions and pre requisites for effecti&e utili;ation of rigid pa&ement.

Report shows comparison of characteristics of fle4ible and rigid pa&ement*

construction methods of cement concrete pa&ement and economics of

cement concrete and fle4ible pa&ement.

(ontents

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%ertificate 8

+c,nowledgement 0

+bstract ?

%ontent 3

ist of figure @

ist of table

(%apter +escription Page

No No

" Introd&ction

1.1 General A

1.8 #ndiaBs road moderni;ation need A1.0 5a&ement choice 12

4 (onsideration of rigid pavement from t%e point of special

re9&irement of expressway

8.1 Traffic safety 11

8.8 Tra&el comfort 11

8.0 -urability 18

8.? Maintenance need 18

/ Preca&tions and pre re9&isites for effective &tili:ation

0.1 General 10

0.8 !tructural mechanism of cement concrete pa&ement 10

0.0 !pecial en&ironmental condition for concrete 1?

0.? Rigidity of concrete pa&ement 1?

0.3 %onsideration rele&ant to structural and functional aspect 13

; (omparison of c%aracteristics of flexi8le and cement concrete

pavements for expressway 1@

2 (onstr&ction of cement concrete pavement

3.1 %onstruction of 5a&ement slab 83

3.8 %onstruction of (oints 02

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5 Economics of concrete and flexi8le pavement

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-ig&re +escription Page

No No

1 %onstruction method of cement concrete road 8<

8 4pansion (oint 00

0 Carping (oint 00

? ongitudinal (oint 0?

3 %ontraction (oint 0?

*ist of ,a8le

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,a8le +escription Page

No No

1 5a&ement thic,ness 0<

8 %ost of materials 0<

0 9ormulae for costs of e4pressway pa&ements 0@

? %omparison of initial cost of fle4ible and rigid pa&ements for 0@

e4pressway

3 %omparison of life:cycle cost of fle4ible and rigid pa&ements for 0

e4pressway

(%apter "

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Introd&ction

" " General

Need of e4press way systemD

#n&ention of wheel was a giant step in the history of man,ind. Then onward the man applied all

his resources to mo&e these wheels faster and faster. Now a days speed* comfort and safety are

&ital in transport sector. The national highway system is designed to cater for traffic with 122 ,m

speed. 7owe&er the actual operating are ne&er more than ?2,mph due to rapid increase in

&ehicular traffic and carriage way being shared by both slow and fast traffic. The appropriate

solution lies in construction of e4pressway with control of access and allowing only fast mo&ing

&ehicles. The first national e4pressway between +hmedabad and =adodara has been ta,en up for

construction in #ndia.

" 4 India=s road moderni:ation need

+s #ndiaBs economy growing fast* road transport demand rises. The present networ, of arterial

road is un able to cope up with e&en present need for transport* let alone the future demands.

Moderni;ation of #ndiaBs road* and particularly the construction of a system of super fast

e4pressways* is long o&erdue. 5lans are being drown up for e4pressway.

" / Pavement c%oice

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4pressways are costly to build and maintain. Eecause of a substantial &olume of commercial

&ehicles li,ely to use facility* the pa&ement structure has to recei&e careful consideration in

design and choice of materials forming the pa&ement. 5a&ement costs constitute a significant

proportion of total cost of highway facility. 7ence* great care is needed in selecting right type

of pa&ement and specification for the &arious courses that ma,e up the pa&ement. #n

e4pressway schemes* a matter that should not be lost sight of is the cost of maintaining the

pa&ement* including routine repairs* periodic renewals and o&erlays. Maintenance operations

in e4pressway routes can cause considerable in con&enience and annoyance to users*

especially if the facility is toll based. +n entrepreneur who in&ests money on a toll based

e4pressway would prefer to minimi;e his in&ol&ement with maintenance operation to the

barest le&el. The choice of pa&ement type* whether fle4ible or cement concrete* therefore* has

to be &ery carefully e4ercised.

(%apter 4

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(onsideration of rigid pavement from t%e point of special

re9&irement of expressway

4 " ,raffic safety

5a&ement associated traffic safety factors include s,id resistance* drainability against

hydroplaning* and night &isibility. %ement concrete pa&ement has distinct initial ad&antage

o&er bitumen pa&ement in this regard* as surface te4turing forms integral part of the normal

construction practice for such pa&ements. They also ha&e superior night &isibility by &irtue

of their lighter colour. -urable surface te4ture with long life * not difficult to ensure* though

it calls for attention to number of factors. Restoration of lost te4ture Frete4turing howe&er

calls for special technology and can be quite costly. #n area of low rainfall intensity*

hydroplaning not being the go&erning consideration* it a possible to design the concrete mi4

for adequate s,id resistance e&en after the loss of te4tured surface finish* sub(ect to

a&ailability of appropriate quality material.

4 4 ,ravel comfort

Tra&el comfort is go&erned by le&el of surface e&enness of the pa&ement which go&erns its

riding quality. The concrete pa&ement can pro&ide a &ery e&en surface with manual finishing

operations* within stipulated tolerance of 0 mm under a 0 m straight edge. !ub(ect to

adoption of appropriate precautions during construction to ensure wear resistance* they retain

their profile by &irtue of their inherent rigidity* and pro&ide a fairly constant riding quality

o&er long periods. 7a&ing high shear resistance* are not prone to sho&ing or potholingassociated with fle4ible pa&ements. nsuring good initial surface profile and proper

construction and maintenance (oints need particular attention in this regard.

4 / +&ra8ility

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5oorly designed and constructed concrete pa&ements are ,nown to ha&e &ery long

ser&ice life. The cement concrete road constructed in the country in the past* though

e4tremely limited in length* ha&e an e4cellent ser&ice trac,* ha&ing gi&en good ser&ice

under condition much se&er than those for which they are originally intended. The

thinner once among these ultimately succumbed as much under bitumen repair

technology which is not appropriate to them* as under hea&y traffic. +dequate design and

good construction practice with needed quality control can together pro&ide durable

concrete pa&ements with long ser&ice life and needed le&els of traffic safety and tra&el

comfort.

4 ; $aintenance need

The routine maintenance needs of concrete pa&ements are limited to ensuring a good

(oint seal. )se of superior synthetic (oint seal could substantially cut down the frequency

and e4tent of needed periodic resealing. 9or any local defects or inadequacies de&eloping

o&er long use* appropriate and e4peditious technologies are a&ailable* which can be

utili;ed effecti&ely in preference to bituminous repairs. Cith some maintenance andrepair needs* concrete pa&ements also ha&e the potential ad&antage of practically no

disturbance or dislocation to traffic for attending to related operations.

(%apter /

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Preca&tions and pre re9&isites for effective &tili:ation of rigid

pavement for expressways

/ " General

The special requirements for effecti&e utili;ation of rigid pa&ement are emanate from

following factorsD

$a' The structural mechanism of concrete and concrete pa&ements.

$b' !pecial en&ironmental conditions of pa&ing concrete.

$c' The rigidity of concrete pa&ements.

/ 4 Str&ct&ral mec%anism of concrete and concrete pavements

%ement concrete de&elops &ery fine* small* discontinuous micro:crac,s in initial stages

due to hydrothermal changes. )nder increasing or repetiti&e loading* the micro:crac,s

tend to e4tend and (oin* resulting in fracture and failure. To minimi;e them inherentmicro:crac,ing* only minimally essential water for ensuring full compaction of concrete

should be used. 9ull of saturation concrete during the 8 days curing period is also

imperati&e* as capillary pores in concrete with low water cement ratio are not continuous*

and if once dried* subsequent immersion dose not result in penetration of water therein*

resulting in lower strength and fatigue resistance.

/ / Special environmental conditions of paving concrete .

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%oncrete pa&ements ha&e a large surface to &olume ratio* era e4posed to atmosphere on

one face* with the lower face being in contact with the ground. !uch condition lead to

higher susceptibility to shrin,age* calling for adoption of minimum feasible water and

cement compatible with the required strength and its reali;ation* as also for due attention

to curing to ob&iate early shrin,age crac,ing. The temperature differential and the

resultant warping resistant stresses to which concrete pa&ements are sub(ect* due to

different espouser conditions of its two faces* considerable reduce the concrete strength

a&ailable for supporting the traffic load and catering to their fatigue effects* calling for

high strength concrete.

/ ; Rigidity of concrete pavement

The rigidity inherent in concrete as a structural material enables concrete pa&ements to

maintain an e4cellent functional stability o&er long period in terms of their surface

profile. Chile such stability is a great asset in case of pa&ements constructed to correct

profile* it can become a serious liability in the correction of a substandard surface* the

methods a&ailable for the purpose not being simple* e4peditious or economical.

mphasis on quality assurance initially is* therefore* &ery important* weather throughappropriate mechani;ation or strict super&ision and control of manual surface finishing

operations.

/ 2 (onsiderations relevant to str&ct&ral and f&nctional aspect of rigid

pavements

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/ 2 " Pavement design

Chile concrete pa&ement ma,es more efficient use of constructional material* particularly aggregates* as compared to bituminous pa&ement* they are much more

sensiti&e to o&erloading in terms of damage to the pa&ement structural strength. The

concept of equi&alent standard a4el loads $ !+ s'* which is based on functional criteria*

does not adequately their structural response and is not the appropriate criteria for their

design.

/ 2 4 (oncrete mix design

%oncrete mi4 design for e4pressway should based on both the structural and functional

requirements of such pa&ements. #t should not ha&e the requisites fle4ural strength* but

should also pro&ide needed wear resistance and s,id resistance. Chile ,id resistance of

new pa&ement would mainly depend upon the te4turing of the surface* the materials /

particularly the aggregate would be so selected as to ensure adequate s,id resistance e&en

after the initial te4ture wears off. Chere such materials are not readily a&ailable* two

layer bonded construction may be considered* with the more wear and s,id resistant mi4

design adopted for upper layer.

/ 2 />&ality control of constr&ction

9or e4peditious construction of substantial lengths of e4press way* highly mechani;edconstruction technology would need to be adopted. %entral mi4ing and batching plant*

transit mi4tures* and pa&ing and finishing trains can ob&iate much of the &ariability

associated with manual or semi:mechani;ed construction. 7ow e&er constant chec, on

the supplies of fresh material* and the strength and wor,ability of concrete would need to

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be ensured* e4peditiously introducing any modification to the mi4 design by the test

chec,. %omputeri;ation of the quality control data* and software and the e4port systems

for analysis and interpretation of the data and arri&ing at the needed ad(ustments

Fcorrecti&e action should form an integral part of such quality control system.

/ 2 ; $aintenance and re%a8ilitation

+s indicated earlier* cement concrete need &ery little routine maintenance* while

confined practically renewal of the (oint seal. +ny (oint spalls or contraction crac,s are

best maintained using resin repair technology. 9or surfacing or o&er laying of sound

concrete pa&ements to impro&e their riding quality or enhance their structural strength*

bonded concrete technology is a&ailable* pro&ided it is feasible to close the lane under

such reno&ation to traffic for the requisite construction period including curing.

(%apter ;

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(omparison of c%aracteristics of flexi8le and cement concrete

pavements for expressway

!a# +esira8le Properties of a good Pavement

+ highway pa&ement is designed to support wheel loads imposed on it from traffic

mo&ing o&er it. +dditional stresses are also imposed by changes in the en&ironment. 9or

satisfactorily performing these functions* the pa&ement should ha&e many desirable

characteristics. These are"

1' The pa&ement should ha&e a long life.

8' -uring its design life* it should perform satisfactorily* without suffering e4cessi&e

deformations and rutting.

0' The pa&ement should be structurally sound to withstand the stresses imposed on

it.

?' #t should be sufficiently thic, to distribute the loads and stresses to a safe &alue

on the subgrade soil.

3' #t should pro&ide a reasonably hard wearing surface* so that the abrading action

of wheels $pneumatic and irontyred' does not damage surface.

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1?'The analyses of stresses and strain in a pa&ement should be simple and well:

understood* ma,ing the design precise.

13' The pa&ement should permit easy repairs to utili;e that may be laid underneath it.

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the performance of the pa&ement. #t can well be said that the /deterioration of the

fle4ible pa&ement starts right away with its being thrown open to traffic. The rate of

deterioration is go&erned by the &olume and nature of traffic and the initial quality of

construction it self. Eut* in the case of a concert e pa&ement* deterioration is hardly

perceptible and one can e4pect a consistently uniform performance through out its life.

!d# Str&ct&ral so&ndness

Cell designed pa&ements* whether fle4ible or rigid* are able to withstand the stresses

imposed on them. No superiority can be claimed for a particular pa&ement type on this

score.

!e# Ade9&acy for load +istri8&tion?

Though each of the two types of pa&ements act in a different way their thic,ness are so

ad(usted that the loads get distributed to a safe &alue on the sub grade soil. The fle4ible

pa&ement has only to ha&e a much higher thic,ness than the concrete pa&ement to

accomplish this tas,.

!f# Hard wearing s&rface

Cearing surfaces of pa&ements are sub(ected to hard abrading action of wheels. !e&ere

abrasion ta,es place* particularly on cur&es* and (unctions. %oncrete is a much superior

material than bituminous surface in this regard.

!g#Riding 9&ality

+ good riding quality is a prime requirement of roads surfaces from &arious

considerations. + smooth surface ensures rider comfort* particularly* at high speeds.

=ehicle operating costs are low on smooth roads* fuel consumption being one of the

components of these costs. %oncrete roads and bituminous surfaces* constructed to

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modern specifications pro&ide a smooth riding quality when constructed. Eut* whereas a

concrete pa&ement maintains its initial quality throughout its life* a bituminous surface

deteriorates in riding quality as traffic mo&es o&er it. #n quantitati&e terms* both

pa&ements types when initially constructed can ha&e a roughness &alue of around 8222

mm F ,m as measured with a bump integrator. >n a concrete road* one can e4pect the

same surface smoothness to continue o&er its life. #n contrast* the roughness increases on

a bitumen surface and rutting cased by densification of the layer forming the pa&ement.

%onsequently* with in a short period of 8 / 3 year* roughness &alues can reach &ales as

high as 3222 mm F ,m* necessitating the pro&ision of a light bitumen treatment to restore

original riding quality. The effect is that riding comfort suffers and &ehicle operating cost

increase on a fle4ible pa&ement

!%# Energy conservation

)nder the pre&ailing world wide concern for energy conser&ation* a road surface that

leads to energy sa&ing must get precedence. %oncrete surface results in less fuel

consumption than bitumen surface in two ways. 9irstly* the consistently smooth surface

of a concrete road gi&es a fuel economy of up to 3 . !econdly* concrete surfaces are

rigid and do not deflect to bowl shapes as a fle4ible does under a hea&y load. Chen a

deflection bowl is caused* the wheel has to climb o&er the depression* absorbing energy

losses in the process. #t has been found from a recent study in ).!.+. that a sa&ing in fuel

up to 82 is possible by adopting concrete roads in place of fle4ible pa&ements. )sing

these study results* it has been shown that a concrete pa&ement pays for it self through

full sa&ing alone in a short period of se&en years. Chen #ndia is reeling under fuel crisis*

this single factor should lead to a decision that all future 4pressway pa&ements should

be in concrete.

!i# s'id@resistance

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#n a bituminous surface* loss of s,id:resistance can be o&ercome by pro&iding a surface

treatment of suitable properties. #n concrete pa&ements* the original te4ture can get

smoothened by traffic causing slipperiness. Restoring the te4ture can then be achie&ed

by groo&ing or acid etching. + carefully constructed concrete pa&ement can retain its

te4ture for many years.

! #Impervio&sness to water

Eecause of its dense mass* water can not penetrate through a cement concrete pa&ement.

#f (oints are well sealed* ingress of water through them can also be pre&ented. %oncrete pa&ements* therefore* en(oy imper&iousness to water / a property highly &aluable in

regions of hea&ily rainfall and flood:prone locations. The same cannot be said in respect

of bituminous surfaces. The &oids in the mi4ture* crac,s and potholes allow water to

penetrate into the lower layers and the subgrade.

! # Reflectivity properties

Eeing light colored* concrete offers good reflecti&ity property so that night dri&ing

becomes safer. >n the other hand* bituminous surfaces are dar, colored and do not

reflect the &ehicle light or street light adequately.

!l# (onservation of nat&re=s reso&rces

Road construction consumes natureBs resources in large quantities. Though #ndia has

good reser&es of stone* gra&el* moorum and sand* yet there are regions where stone

materials are &ery scarce $e.g. Gangetic plains* Tripura* Mi;oram etc.' e&en where stone

aggregates are a&ailable in abundance* rec,less use of these materials should be a&oided.

Thus* when there is a choice* a pa&ement type which consumes the least quantity of

stone materials should get preference.

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!m# Availa8ility of 8inder

Eitumen and cement are the principal blinders for highway construction. Chereas

cement is a fully indigenous product* bitumen is deri&ed from petroleum* much of which*

imported by #ndia. Eesides* #ndian crude lac, in bitumen content. The world wide #ndian

crude is becoming more and more difficult as the reser&es get depleted. >n the other

hand* cement is produced from limestone of which the country has good deposits. The

cement industry in #ndia has now moderni;ed itself and there is a surplus of cement

production e&en at less than 2 per cent capacity utili;ation. This is a good opportunity

for introducing cement concrete roads in the country* and there can not be a better

beginning than the e4pressway system.

!n# $aintenance cost

#t has been mentioned earlier that fle4ible pa&ements suffer deformations under traffic*

causing* rutting* crac,ing* ra&eling and potholing. -eterioration sets in the moment the

road is opened to traffic* necessitating constant maintenance effort. +s the riding quality

becomes unbearable for the traffic and as the &ehicle operating costs mount* it is timely

for an inter&ention with a surface renewal course. 5erhaps at the end of 12 years* a

strengthening layer might also be needed. The routine maintenance li,e patch repairs and

surface renewal can cost up to Rs. 82*222 per ,m of two lane road. +s against this*

&irtually no maintenance is needed for a cement concrete pa&ement. The little attention

at (oints costs as little as around Rs. 8222 per ,m. the implications of reduced

maintenance in terms of cost and reduced delay to traffic with a concrete road option are

not inconsiderable.

!o# Initial cost

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9le4ible pa&ements can be constructed in stage. Eut this is an ad&antage which can be

a&ailed of only on lower category road* and certainly not on e4pressways. >n

e4pressways the full requirement of pa&ement needs to be pro&ided at the start it self.

!p# +esign precision

Though recent ad&ances in pa&ement design ha&e rendered the analysis of stresses and

strains in pa&ements &ery precise* the design of fle4ible pa&ement is still largely based

on empirical methods. The characteri;ation of &arious materials in a fle4ible pa&ement

difficult. >n the other hand* concrete is a material whose properties are well understood*

ma,ing it easy to analyse the stresses and strains accurately.

!9# Repairs of &tilities

Many utility ser&ices li,e telephone cables* electricity cables* water pipes and sewers are

laid underneath the road pa&ement. +ny repairs to or remodeling of these in&ol&es

cutting open the road pa&ement. This is easily done in a fle4ible pa&ement* but is

difficult in concrete roads. #n e4pressway* a little bit of planning can easily get o&er this

problem* either by laying ducts to accommodate the utilities or by clustering the utilities

at one place across the road where a fle4ible width can be laid.

!r# Spillage of petrole&m prod&cts

%oncrete is unaffected by spillage of petroleum products* but bituminous surfaces are.

Thus* the dripping of oil from &ehicles can cause disintegration of bituminous surfaces

easily.

!s# (onstr&ction tec%nology

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To ma,e good pa&ements for e4pressways* a high le&el of technology is a must.

quipment needed for bituminous construction is by and large being manufactured in

#ndia. #t is a good coincidence that concrete pa&ing equipment too is being manufactured

in #ndia to meet the needs of concrete road constructionD more modern concrete pa&ing

equipment can also be introduced in the country. 5roduction of high strength concrete is

a well:,nown process in #ndia and there should be no difficulty to ta,e up concreting

(obs for road construction.

(%apter 2

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(onstr&ction of cement concrete pavement

2 "(onstr&ction of Pavement sla8

=arious specifications for construction of cement concrete pa&ement are listed below.

1 %ement grouted layer

1 Rolled concrete layer

8 %ement concrete slab

1. %ement grouted layer

#n cement grouted layer open graded aggregate mi4 with minimum si;e of aggregate as

1 to 83 mm is laid on the prepared subgrade and the aggregate are dry rolled. The loose

thic,ness is compacted to pro&ide 2 of rolled thic,ness. The grout made of course

sand* cement* water is prepared. The proportion of cement to sand is ta,en as 1"1.3 to

1"8.3. To pro&ide proper fluidity to grout* wetting agent is added to the mi4. The grout is

applied on the surface and is allowed to seep through the aggregate matri4.

8. Rolled concrete layer"

#n rolled concrete layer* lean mi4 concrete is used. ean mi4 of aggregate* sand* cement

and water is prepared and laid on prepared subgrade and sub base course. The rolling is

done similar to CEM construction. The loose thic,ness of concrete is 82 more than

the compacted or finished thic,ness. Tandem roller is recommended. The rolling

operation is completed before the final setting of cement. %uring is done as per

con&entional method.

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0. %ement concrete slab"

There are two modes of construction of cement concrete slab

#. +lternate bay method

##. %ontinuous bay method

+lternate bay construction method of construction means constructing bay or one slab in

alternation succession lea&ing the ne4t or intermediate bay to follow up after a gap of one

wee, or so.

+s shown in fig. in alternate bay construction the slabs constructed are in

sequence of 4* y* ; etc. lea&ing the gaps of bay 4 B* y H *; Hetc. This technique pro&ides

additional wor,ing con&enience for laying of slabs. The construction of (oints is easier.

fig " (onstr&ction met%od of cement concrete road

Eut it has many drawbac,s as follows"

$1' arge number of trans&erse (oint is to be pro&ided. This increase the construction cost

and reduces the smooth riding quality of surface.

$8' -uring rain* the surface water collected on the subgrade between the finished bays.

$0' The construction is spread o&er full width of road and traffic has to be completely

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di&erted.

#n continuous bay method all the slab or bay are laid in sequence .i.e 4B*y*;B*.

(ONS,R (,ION S,EPS -OR (E$EN, (ON(RE,E PA)$EN, S*AB

1. 5reparation of sub grade and sub:base

The sub grade or sub base for laying of concrete slab should comply with the following

requirementsD that no soft spots are present in the sub grade or sub baseD that the

uniformly compacted sub grade or sub base e4tends at least 02cm on either side of the

width to be concretedD that the sub grade is properly drainedD that the minimum modulus

of sub grade reaction obtained with a plate bearing test is 3.3? ,gFcm 8.

The sub grade is prepared and chec,ed at least two days in ad&ance of concreting. The

sub grade or sub base is ,ept in moist condition at the time when the cement concrete is

placed. #f necessary* it should be saturated with water for < to 82 hours in ad&ance of

placing concrete. Cater proof paper may also be placed whene&er the cement concrete is

laid directly o&er the soil sub grade. #n such a case* the moistening of the sub grade prior

to placing of the concrete is not required.

8. 5lacing of forms

The steel or wooden forms are used for the purpose.

The steel forms are of M.! channel sections and their depth is equal to the thic,ness of

pa&ements. The section has a length of at lest 0 m e4cept on cur&es less then ?3.2 m

radius* where shorter section is used. Chen set to grade* the ma4imum de&iation of top

surface of any section from a straight line is not e4ceeding by 0 mm.

Cooden frames are dressed on sideD these ha&e minimum base width of 12 cm pf slab

thic,ness of 82 cm and a minimum base width of 13 cm for slab o&er 82 cm thic,. The

forms are (ointed neatly and are set with e4actness to the required grade and alignment.

!ufficient rigidity is obtained to support the form in such a position during the entire

operation of compacting and finishing that they do not de&iate more then 0mm from a

straight edge 0 m in length.

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0. Eatching of material and mi4ing

+fter determining proportions of ingredients for the field mi4* the fine aggregate and

coarse aggregate are proportioned by weight in a weigh:batching plant and placed in to

the hopper along with the necessary quantity of cement. %ement is measured by the bag.

+ll batching of material is done on the basis of one or more whole bag of cement* the

weight of one bag is ta,en as 32 ,g or the unit weight of cement is ta,en as 1??2 ,gFm0.

The mi4ing of cement concrete is done in batch mi4er which will ensure a uniform

distribution of materials through out the mass* so the mi4 is uniform in color and is

homogenous.

The batch of cement* fine aggregate and coarse aggregate is lead together in to the

mi4ture. The water for mi4ing is introduced in to the drum within the first 13 second of mi4ing. The mi4ing of each batch is commenced within one and half minute after all the

materials are placed in mi4ture.

?. Transportation and placing of concrete

The cement concrete is mi4ed in quantities required for immediate use and is deposited

in soil sub grade or sub base to required depth and width of the pa&ement section within

the frame wor, in continuous operation. %are is ta,en to see that no segregation of

materials results while the concrete is being transported from mi4ture to its placement.

The spread is done uniformly. + certain amount of re distribution is done with sho&els.

Needle &ibrator is employed in lieu of Roding splicing of the concrete.

3. %ompaction and finishing

The surface of pa&ement is compacted either by means of a power dri&en finishing

machine or by a &ibrating hand screed. 9or areas where the width of slab is &ery small as

at the corner of road (unctions e.t.c.hand consolidation and finishing may be adopted"

$a' %oncrete* as soon as placed* is struc, off uniformly and screeded to the crown

and cross section of the pa&ement to conform the grade.

$b' The tamper is placed on the side form and is drawn ahead in combination with a

series of lifts and drops to compact the concrete.

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9loating and straight edging

The concrete is further compacted by means of the longitudinal float.

The longitudinal float is held in a position parallel to carriageway center line and passed

gradually from one side of pa&ement to the other. +fter the longitudinal floating is done

and e4cess water gets disappeared* the slab surface is tested for its grade and le&el with

the straight edge.

Eelting* brooming and edging

Iust before the concrete become hard* the surface is belted wit a two ply can&as belt. The

short stro,es are applied trans&ersely to the carriage way.

+fter belting* the pa&ement is gi&en a broom finish with fiber broom brush. The broom is pulled gently o&er the surface of the pa&ement trans&ersely from edge to edge. Erooming

is done perpendicular to the centre line of pa&ement.

Eefore concrete de&elop initial set* the edge of the slab are carefully finished with an

edging tool.

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Chen the concrete attains the required strength or after 8 days of curing the concrete

road is open to traffic.

$!ource" 3'

2 4 (onstr&ction of oints

+esign of oints

Need for (oints

%oncrete pa&ements are sub(ected to &olumetric changes produced by temperature&ariation* shrin,age during setting and changes in moistures content. #f a long slab is

built* it is bound to crac, can only be built if it is di&ided into mall slab by interposing

(oints. These (oints will then ensure that the stresses de&eloped due to e4pansion*

contraction and warping of the slab are with in reasonable limits.

Types of (oints"

Ioints concrete slab are of four types

1. 4pansion (oints

8. %ontraction (oints

0. Carping (oints

?. %onstruction (oints

3. ongitudinal (oints

Requirements of (oints"

Eefore the detailed description of each type of (oint is gi&en* it is appropriate to outline

the general requirement of all types of (oints. They are"

1. The (oint must permit mo&ement of the stabs without restraint.

8. The (oints should not unduly wea,en the slab structurally and the load should be

transferred from slab to anther effecti&ely.

0. The (oints must be sealed to e4clude water* grit and other e4ternal matter.

?. The riding quality of the pa&ement should not be impaired.

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3. The construction of the (oints must interfere as little at possible with lying of the

concrete.

" Expansion oints?

4pansion (oints* as the name itself signifies* are intended to pro&ide space in the

pa&ement for e4pansion of the slabs. 4pansion ta,es place when the temperature of the

slab rises abo&e the &alue when it was laid. #t is normally a trans&erse (oint. 4pansion

(oints also reli&e stresses caused by contraction and warping. 4pansion (oints are

omitted altogether in modern practice

4 (ontraction oints

Chen the temperature of concrete falls below the laying temperature the slab contracts.

#f a long length of slab is laid* the contraction induces tensile stresses and the slab

crac,s. #f (oints are pro&ided at suitable inter&als trans&ersely* the appearance of crac,s

at places other than the (oints can be eliminated. %ontraction (oist also relie&e warping

stresses to some e4tent.

/ 7arping oints

Carping (oints* also ,nown as hinge (oints* are (oints which are intended to relie&e

warping stresses. They permit hinge action but no appreciable separation of ad(acent

slabs. Carping (oints can be longitudinal or trans&erse. + ma(or difference between the

warping (oints and the e4pansion or contraction (oints is that in the former appreciable

changes in the (oints width are pre&ented.

; (onstr&ction oint

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+ construction (oint becomes necessary when wor, has to be stopped at a point where

there would be otherwise no other (oint. #t is ad&isable to plan a dayBs wor, such that the

wor, stops at a contraction or e4pansion (oints. !uch (oints should be regular in shape*

by placing a cross:form in position. The reinforcement should be continued across the

(oint. + groo&e in the (oints with a sealing compound will arrest the entry of foreign

matter and desirable.

2 *ongit&dinal oints

Chen the pa&ement width is more than* say 3 m* it is necessary to pro&ide a longitudinal

(oint and construct the pa&ement in strips. These (oints allow for warping and une&en

settlement of the sub grade. The &ery purpose of the longitudinal (oints being warpingstresses and une&en settlements* it is &ery necessary to pro&ided for some form of load

transferring de&ice.

!pacing of (oints"

The spacing of (oints is go&erned by a number of factors such as $1' temperature

&ariation* $8' thic,ness of slab and $0' amount of reinforcement pro&ided. The usual

practice in respect of reinforced cement concrete slabs is to space (oints at @.3:83 m and

to ma,e e&ery third or fourth (oint an e4pansion (oints. The remaining (oints are made

contraction (oints.

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-ig 4 Expansion oint

-ig / ,ong&e and groove 7arping oint

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-ig ; B&tt type longit&dinal oint wit% tie 8ar

-ig 2 +&mmy contraction oint

0?

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(%apter 5

Economics of concrete and flexi8le pavement

5 " (omparison of initial cost

=arious studies ha&e been made in #ndia comparing the initial cost of fle4ible and rigid

pa&ements. + fresh re&iew is needed because the cost of material and the other input

undergone changes.Material costs* particularly cost of stone aggregates* cement and bitumen affect the cost

of pa&ement. 9or the purpose of comparison* the cost of materials considered as gi&en in

table 1. !ince stone material costs &ery widely across the country four cases ha&e been

considered. The rates of other material are as per current mar,et &alues. Modern

equipment has been assumed* with appro4imate usage charges with suitable increase to

account for current costs. The computations of cost ha&e yielded &ery useful formulae

which can readily gi&e the cost of the two pa&ement types for e4pressways. These are

gi&en in table 8. Table 0 gi&es a summary of the costs. Table 1 gi&es summery of

pa&ement thic,ness.

#t is seen that"

$1' when stone material are costly* case 0 and case ?* rigid pa&ements are in&ariably

cheaper e4cept for %ER of @ in case 0. +n economy of Rs 8 / 13la,hs per ,m is

possible* depending upon the soil conditions.

$8' Chen the soil condition are poor $%ER 8'* rigid pa&ement emerges as the cheaper

alternati&e through out the country$e4cept case 1'

$0' Chen the aggregate are cheap $case 1' and the soil condition are good $%ER 3 and

@'* rigid pa&ements are costlier than fle4ible pa&ements.

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,a8le "? Pavement t%ic'ness

-lexi8le pavement t%ic'ness in !mm#

!ub:base Macadam baseCet mi4

-enseEituminousMacadam

+spheltic%oncrete

Total

%ER"8

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9le4ible 5a&ement%ER"8 %ost J

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and at present &alue for the two pa&ements are gi&en in table. The maintenance costs are

assumed as Rs ?2*222 per 6m for bituminous pa&ements and Rs ?222 per 6m for

concrete pa&ements.

The conclusion from life cycle cost analysis is that concrete rods will able to bring about

considerable sa&ing o&er the design period for all cost of aggregates and all soil

conditions

+dded to the abo&e sa&ings are the sa&ings in fuel* which are also of a &ery high order.

,a8le? 2 (omparison of life@cycle cost of flexi8le and rigid pavements for expressway

!Rs per 'mC ; lanes#

5a&ement type +ggregate

%ost"

%ase1 %ase8 %ase0 %ase?

%ER" 89le4ible 3.

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+s regards cost* they compare &ery fa&orably with bituminous pa&ements e&en in initial

cost. Chen whole life:cycle costs are considered* their cost ad&antages is &ery attracti&e.

+s an added benefit* they gi&e fuel economy.

7ence* concrete pa&ements en(oy many ad&antages and can be a good specification for

#ndiaBs 4pressway programme.

References

$1' 6adiyali . R. “5rinciples and practice of a highway engineering” 6hanna Tech.

5ublications* -elhi* 1A A.

$8' “Road user cost study in #ndia* final report*” central road research institute* New

-elhi 1A 8.

$0' “Modernisation of #ndiaBs road through cement concrete pa&ement*” cement

manufacturersB association* New -elhi* 1A .

$?' %ha,ra&arty* !.M.and 6adiyali* .R.* “ conomics of concrete roads* #ndian concrete

(ournal”* Eombay* 1A A.

0A

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$3' “7ighway engineering” by !.6.6hanna and %. .G.Iusto Nem chand 5ublication

8222.