chapter - 6 highway ii.pptx

8/16/2019 CHAPTER - 6 HIGHWAY II.pptx

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STABILIZED

PAVEMENT

MATERIALS HIGHWAY II - Stabilized Pavement Materials

1



STABILIZED PAVEMENT MATERIALS

HIGHWAY II - Stabilized Pavement Materials

2

Problem Soils categorizes subgrade materials wit low strengt! oroter un"avorable #ro#erties suc as$ e%#ansive soils dis#ersive soils

organic soils saline soil or #resence o" saline water

&ese soils re'uire s#ecial treatment be"ore acce#tance in#avement "oundation so tat te( will be re-classi"ied to "all into

one o" te subgrade categories "or te #ur#ose o" #avement design)Soil stabilization is te alteration o" te #ro#erties o" an e%isting

soil eiter b( blending two or more materials and im#roving#article size distribution or b( te use o" stabilizing additives tomeet te s#eci"ied engineering #ro#erties)





*

Generall(! te ob+ective o" soil stabilization are$ Im#rove te strengt ,stabilit( and bearing ca#acit( "or

subgrade! subbase! base and low- cost road sur"aces!

Im#rove te volume stabilit( . undesirable #ro#ertiessuc as swelling! srin/age! ig #lasticit(caracteristics! and di""icult( in com#action! etc caused b( cange in moisture!

Im#rove durabilit( . increase te resistance to erosion!

weatering or tra""ic Im#rove ig #ermeabilit(! #oor wor/abilit(! "rost

susce#tibilit(! etc





0

&e "actors tat sould be considered in soil stabilizationinclude$ P(sical and cemical com#osition o" te soil to be

stabilized! Availabilit( and economical "easibilit( o" stabilizing agents! ase o" a##lication! Site constraints! climate! curing time! and sa"et()

Suc "actors be ta/en into account in order to select te#ro#er t(#e o" stabilization)





3asicall( "our tecni'ues o" soil stabilization are commonl(#racticed in #avement construction) Mecanical stabilization 4ement stabilization!

5ime stabilization! and 3itumen stabilization

&e suitabilit( o" tese metods de#ends on site constraints!materials! climate! and economic "easibilit()

&e stabilizing #rocess wit admi%ture involves te additiono" a stabilizing agent to te soil! mi%ing wit su""icient waterto acieve te o#timum moisture com#action o" te mi%ture!and "inal curing to ensure tat te strengt #otential isrealized)



Mechanical Stabilization


6

Mecanical stabilization is a metod b( wic a soil or gravel ismi%ed wit te original soil in order to im#rove te grading andmecanical caracteristics o" te soil)

It is an im#rovement o" an available material b( blending it

wit one or more material in order to im#rove te #article sizedistribution and #lasticit( caracteristics)

&(#ical materials used "or mecanical stabilization include riverde#osited sand! natural gravel! silt( sands ! sand cla(s! silt cla(s!crused run 'uarr( #roducts! volcanic cinders and scoria!#oorl( graded laterites and beac sands! etc)

Materials #roduced b( blending ave #ro#erties similar toconventional unbounded materials and can be evaluated b(ordinar( metods)





7

&e #rinci#al #ro#erties a""ecting te stabilit( o" com#acted baseor sub-base materials are internal "riction and coesion)

Internal "riction is cie"l( de#endent on te caracteristics o" tecoarser soil #articles! i)e) gravel! sand and silt sizes)

&e coesion! srin/age! swelling and com#ressibilit( are mainl(associated wit te 'uantit( and nature o" te cla( "raction asindicated b( #lastic #ro#erties)

Preliminar( mi% design o" mecanical stabilization is based on#article size distribution! #lastic #ro#erties and strengt tests,438! etc)

Wen unconventional materials are used! more detailed testingand investigation will o"ten be needed and ma( include temodi"ication o" te acce#ted design or s#eci"ication criteria)





9

Particle Size Distribution: -

Wile ma%imum "riction strengt does not necessaril( coincide witma%imum densit(! te acievement o" a ig densit( will generall( #rovide aig "rictional strengt)

A #article size distribution tat results ma%imum dr( densit(! obtained wit

te closest #ac/ing and minimum voids! as been sown e%#erimentall( to"ollow "uller:s e'uation wit te value o" te e%#onent ;n: usuall( <)0 to <)<"or most soils)

&e teoretical ma%imum densit( o" aggregates is obtained wen grain sizedistribution "ollow te =uller ma%imum densit( e'uation o" te "orm$

Were$ # > #ercent #assing sieve size ?d@

> ma%imum sieve size in te material!

n > a constant wic varies between <)0 to <)<)





B

Particle Size Distribution: - Wit some materials suc as gravel! sand and cla(s! ig densities can be acieved wit

;n: values as low as <)**)

=or materials! wit a ma%imum size o" 1B mm! te amount o" "ines #assing te 7Cmsieve will be 6 and 9D "or ;n: values o" <) and <)0 res#ectivel()

In certain cases iger #ercentages o" material #assing te 7 Em sieve ma( #rovide te

best #er"ormance) Wen te #avement design relies on a relativel( low #ermeabilit( in te #avement

courses! te materials used sould be o" #article size distribution witin te limitsestablised b( substituting values o" <)< and <)** "or ;n: in te above e'uation)

&ese limits are su""icientl( wide to allow "or variations tat will inevitabl( occur in"ield mi%ing)

Wen te value o" te e%#onent ;n: is less tan <)**! te "ines content o" te materialma( be e%cessive) A ig "ine content will result in reduced #ermeabilit(! but ma( leadto te develo#ment o" #ore #ressures and conse'uent instabilit( during com#action orin service)

Were ;n: is greater tan <)! te material ma( be #rone to segregation and raveling andtere"ore more di""icult to wor/)





1<

Strenth Tests: -

Stabilized materials ma( be assessed b( strengt tests suitable"or tis #ur#ose at te densit( and moisture conditions#revailing in te #avement during te service li"e)

Prediction o" moisture condition and ence te "ailure envelo#esat moisture conditions brac/eting te e'uilibrium moistureconditions and at te re'uired densit( antici#ated is im#ortant)

&e e'uilibrium moisture conditions to be e%#ected in a#avement ma( be obtained b( e%amining e%isting roadsconstructed "rom materials similar to tose being investigatedand assembling suc in"ormation "or "uture use)

Fne o" te most commonl( used strengt tests is te laborator(438 test)





11

&e selection o" suitable criteria sould ta/e account o" locale%#erience! es#eciall( tat related to te #er"ormance o" localmaterials)

esign o" stabilized mi%tures to reac satis"actor( road

#avement involves$ caracterizing te individual materials! #ro#ortioning tem to "it te selected criteria! ma/ing u# a trial mi%ture to ade'uate investigation and

design! good construction and control testing tecni'ues)&is involves care"ul #ro#ortioning and toroug mi%ing o" te

constituent materials to #roduce a uni"orm unsegregated "inal#roduct wic can be com#acted and "inised in accordance

wit te s#eci"ication)



!e"ent Stabilization


12

4ement is an e""ective stabilizing agent a##licable to a wide rangeo" soils and situations )It as two im#ortant e""ects on soil

beaviors$ 8educes te moisture susce#tibilit( o" soils$ cement binds te #articles greatl(

and reduces moisture induced volume cange evelo# inter-#article bonds in granular materials$ increased tensile strengt

and elastic modulus)

Soil #ro#erties #rogressivel( cange wit increasing cementcontents) =or #ractical reasons! two categories o" cementstabilized materials ave been identi"ied) 4ement modi"ied materials$ cement is used to reduce #lasticit(! volume-

cange! etc! and te inter-#article bonds are not signi"icantl( develo#ed) 4ement bound materials$ cement is used to su""icientl( enance modulus and

tensile strengt) 4ement bound materials ave #ractical a##lication insti""ening te #avement)





1*

SELECTION OF CEMENT CONTENT

&e cement content determines weter te caracteristics o" temi%ture are dominated b( te #ro#erties o" te original soil or b( te(dration #roducts)

As te #ro#ortion o" cement in te mi%ture increases! so te strengtincreases) Strengt also increases wit time)

&e coice o" cement content de#ends on te strengt re'uired! tedurabilit( o" te mi%ture! and te soundness o" te aggregate)

&e minimum cement content! e%#ressed as a #ercentage o" te dr(

weigt o" soil! sould e%ceed te 'uantit( consumed in te initial ione%cange reactions)

It is recommended tat te #ercentage o" cement added sould bee'ual to or greater tan te initial consum#tion o" lime test ,I45!,3ritis Standard 1B20)





10

A number o" "actors in"luence te 'ualit( o" tecement-soil interactions)

&e most im#ortant "actors can be categorized into

"our grou#s$ Nature and type of soil) Cement content) Moisture content.

Pulverization, mixing, compaction, and curingconditions.





1

Nature and type of soil)

&is include$ cla( content ,ma% D #lasticit( o" te soil ,ma%55 o" 0! gradation! content o" organic materials ,ma% 2D!sul#ate content ,ma% <)2D "or coesive soils and 1 D "or non-

coesive soils! and PH content)Soils wit ig cla( content and ig #lasticit( are di""icult to

mi% and ig additive contents are re'uired "or an a##reciablecange in #ro#erties)

Pre . treatment wit lime owever is good metod to allow tesoil to be cementstabilized later)

&e re'uirements wit res#ect to te organic matter! PH! andsul#alte contents are in "act te same as tose wic are used"or concrete)





16

Cement content)

&e cement re'uired to stabilize soils e""ectivel( var( witte nature and t(#e o" soils)

&e criteria used are te com#ressive strengt ,about 1)7MPa a"ter seven da(s)

&e 'uantit( re'uired "or gravel( soils is generall( mucless tan re'uired "or silt( and cla(e( soils)

Generall(! a soils is regarded to be suited "or cement-

stabilized i" te soil as a ma%imum grain size tan 7 mm!#ercents #assing and retained <)<7 mm sieve is less tan*D and greater tan D res#ectivel(! and li'uid and#lastic limits less tan < and 2 res#ectivel()





17

Cement content) 3ased on vast e%#erience on vast e%#erienced on cement stabilization!

te general guidelines in te "ollowing table ave been #rovidedregarding te amounts o" cement tat are needed to stabilize a soil)

Soil type Amount of Cement (%)By Weight By Volume

A-1-1 3 - 5 5 - 7

A-1-b 5 - 8 7 - 9

A- 5 - 9 7 - 1!

A-3 7 - 11 8 - 1A-" 7 - 1 8 - 13

A-5 8 - 13 8 - 13

A-# 9 - 15 1! - 1"

A-7 1! - 1# 1! - 1"





19

Moisture content.

Moisture is re'uired "or (dration o" cement to ta/e#lace! to im#rove te wor/abilit(! and "acilitate tecom#action o" te soil . cement mi%ture)

&e soil-cement mi%ture e%ibit te same t(#e o"moisture . densit( relationsi# as an ordinar( soil) &us!"or a given com#action e""ort! tere is an o#timummoisture content at wic te ma%imum densit( is

obtained)It is! owever! seen tat te igest com#ressive strengt

can be obtained wit s#ecimens com#acted sligtl( belowte o#timum "or ma%imum densit()





1B


Man( #rocedures o" construction are available! but can becategorized into mi%ing in #lant ,in a travelling #lant and

stationar( #lant "or dr( mi%ing! and in #lace mi%ing)&e metods are #rinci#all( te same e%ce#t mi%ing in te "irst

is done in mi%ing #lants and in te later is in-#lace)

8egardless o" te t(#e o" macine used! te #rocedure o" mi%-in- #lace construction involves initial #re#aration o" tesubgrade! #ulverization o" te soil! s#reading o" te soil! dr(-mi% te soil and te cement! adding water and wet mi%!com#act and "inis! and #rotect and cure, #lace a curingmembrane to /ee# moist)





2<


&e in"luence o" te degree o" mi%ing and com#action issel" e%#laining)

Fne sould owever be aware o" te "act tat an( dela( incom#action a"ter mi%ing will ave a negative e""ect)

As wit concrete! curing is an im#ortant "actor in"luencingon te end result)

&e tem#erature sould be ig enoug and te stabilizedmaterial sould be #revented "rom dr(ing out in order toobtain te best result)





21

Since cement stabilized materials constitute in most caseste main structural #art o" #avements! muc attention isgiven to teir mecanical caracteristics suc as$

• &ensile and com#ressive strengt!

• e"ormation beavior! and• =atigue caracteristics

Tensile an# co"$ressi%e strenths: -

&e com#ressive strengt based on te uncon"ined

com#ressive test increases wit te cement content in temi%ture de#ending on te nature and t(#es o" soil)

It as been used to determine strengt o" stabilizedmaterials! but as little a##lication to #avement design)





22

Tensile an# co"$ressi%e strenths: -

438 can be used to evaluate te strengt o" cement modi"iedmaterials! but not "or bound materials)

&ensile strengt is im#ortant in te design o" cement bound materials)

ensit( is also an im#ortant #arameter wic as a direct relationsi# wit te 4S)

4uring tem#erature and curing time! com#action and degree o"#ulverization are im#ortant "actors wic a""ect te strengt gained b(cement stabilization)

&e metod o" com#action is im#ortant "or cla(e( soils)Hig degree o" #ulverization acieved in a sorter #eriod o" time leads

to more intensive reaction between soils and cement and results igstrengt)





2*

De&or"ation beha%ior: - It is well /nown tat cla(s! sands! and gravels sow di""erent elastic

de"ormation beavior under re#etitive loading)

&e addition o" cement on tese materials canges te elasticde"ormation #ro#erties! but not com#letel()

&e #arent material will ave a great in"luence on te #ro#erties o"te soil-cement mi%ture)

4emented cla(e( materials also e%ibit some degree o" #ermanentde"ormation under re#eated loading and a certain amount o" cree#

under stead( loads)4emented sand and gravel e%ibit a similar #er"ormance but

#ermanent de"ormation and cree# are less tan in cemented cla(e(soils) &e less "ines are #resent in te soil mi%ture te more tecement-treated soil beave li/e concrete)





20

'atiue characteristics: - 4ement stabilized materials crac/s eiter due to (dration and

dr(ing srin/age and "atigue at te result o" re#eated tensilestresses ,strains

It as been a##arent tat te #arent soil as a great in"luence onte "atigue caracteristics o" cement stabilized materials)

Altoug tere seems a great variation! tere is indeedsometing li/e a tresold strain level under wic no "atigue will occur)

&e durabilit( test is normal used in te soil- cement mi% design)

urabilit( is de"ined as a loss in weigt o" a s#ecimen a"ter 12"reeze- taw c(cles or 12 wet- dr( c(cles) &e material loss isgenerated b( brusing te sam#les a"ter eac c(cle)



Li"e Stabilization


2

5ime is a broad term wic is used to describe calcium o%ide,4aF- 'uic/ lime calcium (dro%ide 4a,FH2- (drated lime!and calcium carbonate ,4a4F*-carbonate is o" no value "orstabilization)

4ommonl( used #roducts o" 'uic/ lime and (drated lime are(drated calcitic lime ,4aF! dolomitic 'uic/ lime ,4aF MgF)

5ime can be a##lied as dr( (drated! 'uic/ or slurr( lime)

5ime is an e""ective stabilizing agent "or cla(e( to im#rove bot wor/abilit( and strengt)

5ime is not e""ective wit coesion less or low coesion materials witout te addition o" secondar( ,#ozzolanic- "ine materials wic react wit lime to "orm cementations com#oundsadditives)



Li"e Stabilization


26

&e cementitous #roducts resulting "rom cement and limestabilization are wit com#arable beavior and "ollow "airl( similarevaluation! and construction considerations)

&e signi"icant di""erence in te nature and rate o" cementations

reactions! owever! is a basis "or te coice between cement andlime)

3asicall( "our di""erent "actors are involved in te soil-limereaction wic are$ action e%cange! "locculation! #ozzolanicreaction! and carbonation)

4at ion e%cange is an immediate reaction and unli/e #ozzolanicreaction! reaction! it is not signi"icantl( de#endent on tem#eraturein wic cations suc as sodium and (drogen are re#laced b(calcium ions "or wic te cla( mineral as a greater a""init()



Li"e Stabilization


27

It as been sown tat te tic/ness o" te water la(er aroundte cla( #articles decrease substantiall( as te result o" catione%canges)

&is condition te turn #romotes te develo#ment o"

"locculent structures) &is means tat #lasticit(! srin/ageand swelling and oter normal cla( . water interactions aredistinctl( inibited)

&e e""ect o" lime on cla( minerals o" ig cation e%cangeca#acit(! suc as montmorillonite cla(s! is tere"ore morea##arent tan it is on cla( o" low cation e%cange ca#acit(suc as /oalinite cla(s)

4emicall( e'uivalent amounts o" 'uic/ lime and (dratedlime ave te same e""ect on #lasticit()



Li"e Stabilization


29

However! 'uic/ lime as an additional dr(ing e""ect since! tecemical reaction between te lime and te water in te soliremoves "ree water "rom te sol and te eat #roduced b( tereaction assists in dr(ing)

&e cange in #lasticit( is accom#anied an immediate cangein te strengt o" te soil as measured b( te 438)

&e e""ect o" lime on te 438 value increases wit time as te#ozzolanic reactions ta/e e""ect)

Siliceous and aluminous materials in te soil react wit limeto #roduce a gel o" calcium silicates and aluminates)

&is gel cements te soil #articles togeter in a manner tat issimilar to tat o" (drated cement)



Li"e Stabilization


2B

Minerals in te soil tat react wit lime to #roduce a cementingcom#ound are /nown as #ozzolans! it ta/es! it ta/es considerabl(more time tan re'uired "or (dration o" Portland cement)causing continuing strengt im#rovements wit time)

&e cementing action also de#ends on climatic conditions and atoroug com#action o" te mi%ture) Hig curing tem#eraturesave a #ositive e""ect on te #ozzlanic reactions)

&em#eratures lower tan 1* and 16<4 retard te reaction "romtis #oint o" view it is obvious tat lime stabilization is es#eciall(

#o#ular in tro#ical countries)4arbonation occurs wen te (drated lime reacts wit te 4F2

"rom air) 4arbonates ,4a4F* add some strengt but te reaction?eats@ te lime and will a""ect #ozzilanic reactions)



Li"e Stabilization


*<

Fter "actors tat in"luence te soil- lime reaction are$ &e #resence o" e%cessive 'uantities o" organic carbon retards

te lime .soil reaction! Moderatel( weatered and unweatered soils wit ig #H

dis#la( good reactivit(! Poorl( drained soils e%ibit a iger degree o" lime-reactivit(

tan better drained soils! All calcareous soils react satis"actoril( wit lime and

A minimum amount o" cla( a##ro%imatel( 1D is re'uired toinsure an ade'uate source o" silica and or alumina "or telime- soil #ozzolanic reaction)



Li"e Stabilization


*1

&e strengt o" lime stabilized materials is de#endent on te amount o"lime! te curing time! curing tem#erature and com#action)

In addition! te 'ualit( o" water! t(#e o" stabilizing lime! and uni"ormit(o" are im#ortant "actors)

Mi% design #rocedures "or lime stabilization are te determination o" te

ma%imum amount o" lime tat can be ta/en b( te soil be"ore "ree limeoccurs ,te lime content above wic "urter increases do not #roducesigni"icant additional strengt or te lime re'uirement to attain as#eci"ic strengt levels)

4aracteristics related design #rocedures are related to te conditions

"or wic te( ave been develo#ed) Wen lime is used "or subgrade im#rovements! te design lime content

ma( be designated as te lime content above wic no "urtera##reciable reduction in PI occurs or minimum lime content is increased<) to 1)<D to o""set te e""ect o" "ield variabilit()



Bitu"inous Stabilization


*2

3ituminous materials are used as stabilizers to retard or com#letel(sto# moisture absor#tion b( coating soil or aggregate grains in te soil-aggregate mi%ture)

3ituminous stabilization is used wit non- coesive granular materials- were te bitumen adds coesive strengt and wit coesive materials

.were te bitumen ?water#roo"s@ te soil tus reducing loss o"strengt wit increase in moisture content)

3ot e""ects ta/e #lace #artl( "rom te "ormation o" bituminous "ilmaround te soil #articles wic bonds tem togeter and #revents teabsor#tion o" water! and #artl( "rom sim#le bloc/ing o" te #ores!

#reventing water "rom entering te soil mass) 3ecause more care is necessar( in bituminous stabilization to acieve

satis"actor( mi%ing! its use as not been as wides#read as cement andlime stabilization)





**

Bitu"inous "aterials: - &e bituminous materials tat are used "or stabilization wor/s are mostl(

#enetration grade bitumen and cutbac/ bitumen and bitumen emulsion)

&e caracteristics o" cutbac/s de#ended on te #article size distribution o"te soil! te tem#erature o" a##lication! and te t(#e o" mi% #lant)

&e more viscous binders are normall( used "or soils aving onl( a small#ro#ortion o" material #assing te <)<7mm sieve and "or #lant mi%es! wilete ligter binders are used "or mi% .in #lace metods and wit soilscontaining a larger #ro#ortion o" "ines)

mulsions are generall( suitable "or soil stabilization in climate were ra#iddr(ing conditions occur! since tis is e'uivalent to adding water to te soil as

well as bituminous binder)

In te tro#ics! were te tem#erature is ig te use o" emulsions ma( be anadvantage since it el#s to #rovide #art o" te o#timum moisture content "orcom#action! tereb( reducing te amount o" water necessar( "or tis #ur#ose)





*0

Soils re(uire"ents: - 3ituminous materials are used "or te stabilization o" bot coesive and

non-coesive granular soils)

Soils wic can readil( #ulverized b( construction e'ui#ment aresatis"actor( "or bituminous stabilization)

4oesive soils usuall( ave satis"actor( bearing ca#acit( at lowmoisture content) &e #ur#ose o" using bitumen as a stabilizer in sucsoils is to water#roo" tem as a means to maintain tem at lowmoisture contents and ig bearing ca#acities)

In te non-coesive granular materials! bitumen serves as a bonding orcementing agent between #articles)

e#ending on te #article size distribution and #(sical #ro#erties o"te available soil materials and te "unction o" te stabilizing bitumen!tere are "our t(#es o" soil-bitumen mi%tures in igwa( engineering)





*

Soil-bitumen: tis is a mi%ture o" coesive soil and bitumen "or water#roo"ing#ur#oses) &e ma%imum grain size sould #re"erabl( not greater tan one-tird o"te com#acted la(er) &e bitumen re'uirements commonl( range "rom 0-7D o" tedr( weigt o" te soil)

Sand bitumen: sands suc as beac! river! #it! or e%isting roadwa( sand ma( bestabilized wit bitumen i" te( are substantiall( "ree "rom vegetable matter! lum#s

or balls o" cla( or aderent "ilms o" cla() Sometimes it ma( re'uire admi%ture o""iller material to meet mecanical stabilit( re'uirements) &e re'uired amount o"

bitumen content ranges "rom 0-1<D! te o#timum sould be determined b(com#action! strengt! and water resistance testing and sould not e%ceed te #ores#ace o" te com#acted mineral mi%)

aterproofed granular stabilization: &is is a s(stem in wic a soil material

#ossessing good gradation o" constituent #articles "rom coarse to "ine! and avingig #otential densit( is water#roo"ed b( uni"orm distribution o" small amount ,1-2D o" bitumen)

!iled eart": &is is a soil sur"ace! consisting o" silt-cla( material made water andabrasion resistant b( slow or medium curing bitumen cutbac/s or emulsions)





*7

&e mecanism o" stabilization wit bituminous materialsconsists o" adding coesive strengt and reducing te #ercolationo" water!

Jo cemical interaction is ta/ing #lace)

Water#roo"ing occur b( coating te sur"ace o" #articlesaggregated lum#s o" #articles or b( bloc/ing te #ores o" te soilmass! and a strengt comes "rom te #resence o" a continuous"ilm o" bitumen giving coesion)

&ere are two o##osing e""ects . te tinner te "ilm o" bitumen

te stronger te material owever! tic/ "ilm or "illed #ores arete most e""ective in #reventing ingress o" water)

&oo muc bitumen! owever! causes loss o" strengt b(lubricating te #articles and #reventing interloc/)





*9

&e mi% design #rocedure "or bituminous treatments o" soils ma( be considered under "our eadings mi% design "or stabilit( in non-coesive or coesive materials mi% design "or sand-bitumen mi%es! and mi% design "or oiled eart roads)

=or te "irst tree t(#es o" mi%! a series o" tests sould be made wit var(ing bitumen contents and grades using ot bitumen!cutbac/ and emulsion! and te a##ro#riate mi% is selected givingdue weigt to te need "or stabilit( or water resistance asre'uired)

4om#action! com#ressive! and water absor#tion test arenormall( used to select te o#timum amount o" bitumen content)

Ma( di""iculties in construction and #oor #avement #er"ormancema( be attributed to a lac/ o" a##reciation o" tis additive e""ect)



$A&' *

HIGHWAY II St bili d P t M t i l

*B

chapter - 6 highway ii.pptx

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