Highway Engineering TRAN 3001 Lecture 5
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Transcript of Highway Engineering TRAN 3001 Lecture 5
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
1/21
TRAN3001Highway Engineering Lecture
5PAVEMENT MATERIALS
Soil
Types
Phases
Solid Phase
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials
The most imortant avement materials are soil!aggregates o" roc# an$ slag %&y'ro$uct o" metalsmelting(! &ituminous &in$ers an$ Portlan$ cement)Soil*oravement construction! soil is the inorganic!
earthen material that is the "oun$ation "or all roa$s) +tis also e,cavate$ %cut( "rom higher elevations o" aroa$ construction site an$ haule$ %as -ll( to constructem&an#ments to the re.uire$ gra$es)
/here a$e.uate .uantities o" -ll cannot &e o&taine$"rom the earthwor#s on site! inorganic earthenmaterial has to &e imorte$)%The to layer o" mostly organic material is re"erre$ toas tosoil an$ tyically ranges "rom 5 cm to 30 cmthic#) rganic material is unsuita&le "or avementconstruction an$ has to &e remove$ ()
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
Tyes o" oil
oil is the ro$uct o" the hysical an$ chemical weatheringo" &e$roc#) /in$ an$ other natural "orces have move$ alot o" this weathere$ material away "rom their original
locations)ne o" the ways soils can &e groue$ is accor$ing to the
means &y which they were naturally transorte$ an$$eosite$ in their resent locations! e,amles o" which areliste$ &elow)
Residual soilsThese were "orme$ "rom the un$erlying &e$roc# an$ never$islace$) Tyically -ne'graine$ near the sur"ace! thesesoils &ecome more coarse'graine$ with increasing $ethas they contain roc# "ragments)
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Pavement Materials %ont2$(
Tyes o" oil %ont2$(Colluvial soils
Accumulations o" roc# $e&ris which &ecome
$etache$ an$ are carrie$ %&y gravity( $own thesloes "orm these soils which are coarse an$ stonysince they result "rom hysical weathering)
Alluvial soils
These soils have &een $eosite$ &y moving river
waters! mostly onto their 4oo$ lains! which arewi$e! 4at arcels o" lan$ a$acent to the rivers)
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Pavement Materials %ont2$(
Tyes o" oil %ont2$(
Alluvial soils (Contd)As the velocity o" the 4oo$ water $ecreases the
"urther away it gets "rom the river! san$ an$ gravel
+s $eosite$ a$acent to the river &an#s! less coarse
graine$ material "urther out an$ the -nest materialis "urthest "rom the river)
This results in goo$ sources o" construction material
near to the river an$ swamy lan$ "urther out)
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases
oil can &e consi$ere$ as soli$ %mineral(articles interserse$ with voi$6ore saces
which may contain water as well as air)Highway engineering is concerne$ withminimi7ing the voi$ saces an$ ma,imi7ingthe volume occuie$ &y the mineral articles)
egregating the three constituent soil hasesro$uces the "ollowing schematic $iagram8
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases %ont2$(
e 9 :v
:s
whereVoid Ratio = e
:olume o" voi$s 9 :v
:olume o" soli$s 9 :s
Air
/ater
oli$s
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases %ont2$(
/hen the soil is saturate$! all the voi$s are-lle$ with water! i)e) the volume o" voi$s %Vv(
is e.ual to the volume o" water %Vw( an$ thevoid ratio of the saturated soil is es8
es = Vw
Vs+" m is the moisture content o" the soil 8
m = Ww
Ws
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases %ont2$(
Vw = m x s
Vs w
where /w 9 weight o" water
/s 9 weight o" soli$s
s 9 weight er unit volume o" soli$s
w 9 weight er unit volume o" water
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases %ont2$(
Theporosity n! o" a soil is the ratio o" thevolume o" the voi$s to the total volume o" the
soil) This is usually e,resse$ as a ercentage8n = Vv x 1 where : is the total
volume
V o" the soilPorosity can also &e e,resse$ in terms o" e8
n=Vv x 1 = e x 1
Vv! Vs 1 ! e
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases %ont2$(
The ercentage o" the total volume o" the soilwhich is occuie$ &y the air in the voi$s is
re"erre$ to as the percent air voids na!8na = :a x 1 where :a is the volume
: o" air voi$s
The ercentage o" the total volume o" the soilwhich is occuie$ &y the water in the voi$s isre"erre$ to as the percent "ater voids nw!8
nw = Vw x 1 V
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oil Phases %ont2$(#e$ree of saturation S! is the e,tent to whichthe voi$s resent in a soil are -lle$ with water) +tis the ratio o" the volume o" water to the volume
o" voi$s! e,resse$ as a ercentage8S =Vw x 1
:v
The e,tent to which the e,isting voi$ ratio %e( o" asoil reresents the range o" ossi&le voi$ ratios"or that soil is terme$ the de$ree ofcompaction %! or relative unit weight 8
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Pavement Materials %ont2$(
oil Phases %ont2$(
9 emax ; e x 1
emax ' emin
emax 9 voi$ ratio o" soil in its loosest state
emin 9 voi$ ratio o" soil in its $ensest
state
This means that a soil in its loosest state willhave a $egree o" comaction6relative unitweight o" 7ero while in its most comact stateit will have a relative unit weight o" 100
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Pavement Materials %ont2$(
oli$ Phase o" oil
The mineral articles o" soil range in si7e"rom &oul$ers to colloi$s) +n 1=0> the
we$ish soil scientist Atter&erg $evise$ aclassi-cation system which esta&lishe$limiting si7es o" the articles that comrisethe soli$ hase o" soil)
This was an imortant $eveloment as thehysical an$ chemical roerties o" soil arestrongly in4uence$ &y its particle si&e
distri'ution(
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(?ravel articles were classi-e$ as those &etween@0 mm an$ @ mm in si7e! san$ "rom @ mm to 0)@mm! silt 0)@ mm to 0)00@ mm an$ clay less than0)00@ mm)
?ravel was set &etween the limits within which nowater is hel$ in the ore saces an$ only wea#lyhel$)
The lower limit "or san$ %0)@ mm( was the oint atwhich water is hel$ in the ore saces &y caillary
action)*or silt the lower limit o" 0)00@ mm is the smallestsi7e article that can &e seen with the na#e$ eyean$ articles can &e coagulate$ to "orm crum&s)2
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(How coarse or how -ne a soil is $een$s on the
relativeamounts o" the $iBerent "ractions resent)
Review o" the technical literature on soils showsthat
$iBerent organisations %+nternational Cnion o" oilciences! AAHT! etc)( accet that the most
convenientway to $e-ne the various mineral constituents o"
soil ison the &asis o" article si7e)However! e,actly where the limits shoul$ &e set "orsan$! silt! etc) is not universally accete$)
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(
The physical and mineralo$ical characteristics o" soilarticles are imortant in $etermining the suita&ility o"the soil as a avement material)
oil articles are comose$ o" rimary mineral "ragmentstogether with any secon$ary minerals ro$uce$ &yweathering)oil "ractions ro$uce$ &y hysical weathering i)e) gravel!san$ an$ coarse silt are comrise$ mostly o" rimary
minerals) The .uantity o" rimary minerals is re$uce$ inthe -ne silt articles an$ in the clay "raction! thesecon$ary minerals re$ominate)
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(Sand and "#avel are comose$ rimarily o" .uart7%ilicon Dio,i$e! i)( articles an$ are chemically
inactive so the hysical characteristics are o" mostinterest)
The in$ivi$ual grains are generally &ul#y in shae an$$een$ing on the $egree o" hysical weathering
receive$rior to -nal $eosition! may &e angular or roun$)
They $o not e,hi&it any cohesive roerties an$resistance
to $islacement is cause$ &y interloc#ing o" the grains!calle$ inter'granular6internal "riction)
The &ul#iness o" the grains results in relatively large
ores! ma#ing san$y6gravel soils very ermea&le)
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(
Siltarticles are transitional &etween san$ an$ clay)
Physically they are similar to san$s in that their sta&ility is
$erive$ "rom internal "riction! articularly the coarser grains
which are &ul#y with the same $ominant .uart7 mineral)Cnli#e san$s! silts ossess a limite$ amount o" cohesion an$
water asses relatively slowly through the smaller ores)
/here articles at the lower limit o" the "raction re$ominate!
silt e,hi&its .ualities li#e clay an$ may un$ergo consi$era&le
shrin#age an$ e,ansion with changes in moisture content)
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8/9/2019 Highway Engineering TRAN 3001 Lecture 5
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(
lay articles $iBer "rom the other "ractions&oth chemically an$ hysically)
They are 4at an$ elongate$! comrising asilica sheet &on$e$ to an alumina sheet%two layer tye( or a three'layer tye where
two silica sheets are &on$e$ to a centralalumina sheet) %+ron or magnesium may &eresent instea$ o" aluminium()
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Pavement Materials %ont2$(
oli$ Phase o" oil %ont2$(ecause o" their shae they have a much largersur"ace area er unit weight than the &ul#ier"ractions an$ can in4uence a soil2s &ehaviour
seemingly out o" roortion to the amount resentin the soil)
The very small ore saces &etween the articlesma#e clay soils imermea&le "or all ractical
alications)
lay minerals carry negative electrical charges ontheir sur"aces which a$sor& water %hol$ water onthe sur"ace( an$ account "or cohesion! shrin#age
an$ swelling roerties)