Aggregates ENCI579 Lecture4

8/20/2019 Aggregates ENCI579 Lecture4

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Highway Materials, Soils, and Concrete

Aggregates• Soil Definition (Engineering)

– “refers to all unconsolidated aterial in t!e

eart!"s crust# all aterial a$o%e t!e

$edroc&'

• ineral articles (gra%el# sand# silt# cla)

• organic aterial (to soil# ars!es)

• *ggregates – ineral articles of a soil

– secificall# granular soil grou

• gra%el# sand# silt


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Aggregates• ,ranular Soil ,rou (*ggregates)

– -!sical .eat!ering

• action of frost# .ater# .ind# glaciers# lant/anials• articles transorted $ .ind# .ater# ice

• soils fored are called granular soil te

• “grains are siilar to t!e original $edroc&'

– 0arger grain sies t!an clas

– -articles tend to $e ore or less s!eres/cu$es

– 2ound .ater is sall coared to o%erall ass


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Aggregates• ,ranular Soil ,rou (*ggregates)

– a$ilit to ac!ie%e greater densities

• .ell graded granular aterial

– increased soil strengt!

– lo.er erea$ilit

– reduced future settleent

• !ese iro%eents dictate t!e use of

aggregates in a%eent laers .!ere .!eel

loads are greater


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Aggregates• In co$ination .it! as!alt ceent or

ortland ceent to for as!alt concrete or

ceent concrete resecti%el• In su$$ases and $ases of a road.a

structure

• drainage structures

• concrete $loc&s


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Aggregates

• es of *ggregates

• 2asic roerties of t!ese aggregates

• ests used to e%aluate t!ese roerties


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Aggregates• *ggregate Sources

– natural sand or gra%el deosits 6

– crus!ed roc& 6

– slag and ine refuse

– ru$$le and refuse

– artificial and rocessed aterials – ul%eried concrete and as!alt a%eents

– ot!er reccled and .aste aterials


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Aggregates

• Natural sand and gra%el deosits

– sand and gra%el its

– sand and gra%el soils t!at !a%e $een

naturall sorted to eliinate ost of t!e silt

or cla sies t!en deosited in8

• glacier forations (es&ers# out.as! lains)• ri%er deosits

• $eac!es of current and re%ious la&es and seas


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Aggregates• Sand / ,ra%el -it De%eloent

– Striing of tosoil# %egetation fro surface

– E:ca%ation of aterial

• aterial is loose ; front end loaders

– Crus!ing of t!e aterial

• larger sie aggregate is $ro&e do.n to desired sie

• crus!ed gra%el is considered !ig!


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Aggregates• Crus!ed ?oc&

– “e of aggregates roduced fro


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– Igneous ?oc&s

• Ariginal $edroc& fored fro t!e cooling of olten

aterial

• Coarse grained igneous roc& (granite) cooled slo.l

• Bine grained igneous roc&s ($asalt) cooled raidl

– Sedientar ?oc&s

• Solidification of c!eical or ineral sedients deosited

under ancient seas

• 0aered since original aterial .as deosited in t!is

anner


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– Sedientar ?oc&s

• 0iestone Calciu Car$onate• Doloite Calciu/@agnesiu Car$onate

• S!ale Cla

• Sandstone uart

• C!ert Bine sand

• Congloerate ,ra%el


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– @etaor!ic ?oc&s

– Igneous or Sedientar roc&s t!at !a%e $eenetaor!osed due to intense !eat and

ressure

• Slate s!ale

• @ar$le liestone

• uartite sandstone

• ,neiss granite


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– Igneous and @etaor!ic roc&s are %er !ard and

a&e an e:cellent source for aggregates

– 0iestone and Doloite are coon sedientar

roc&s# are softer t!an igneous roc&s $ut are

acceta$le for aggregates

– S!ale riaril coosed of cla grains is .ea&and disintegrates easil

– C!ert also disintegrates easil


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Aggregates

• uarr -it De%eloent

– Aening and Striing of t!e face of t!e


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Aggregates• Slag and @ine ?efuse

– Slag is a .aste aterial resulting fro t!e treatent

of ore to roduce iron# steel# nic&el# ==

• 2last furnace slag fro iron ills is a coonaggregate

– @ine tailings can also $e used for aggregates

• ?u$$le and ?efuse

– reccling of ul%eried concrete fro structures

– reccled as!alt a%eents in $ase courses

– reccled ru$$er# crus!ed glass in $ase courses


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Aggregates• es of *ggregates

– Bine *ggregate

• aggregate articles ainl $et.een t!e 4=75 sie and t!e 75u sie%e=

– Coarse *ggregate

• aggregate articles ainl larger t!an 4=75

– -it ?un

• aggregate fro a sand or gra%el it .it! no

rocessing


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Aggregates• es of *ggregates

– Crus!ed ,ra%el

• it gra%el (or sand) t!at !as $een ut t!roug! acrus!er eit!er to $rea& t!e rounded gra%el articles

into saller sies or to roduce roug!er surfaces

– Crus!ed ?oc&

• aggregate fro t!e crus!ing of $edroc&= *ll articles are angular and not rounded as in gra%el

– Screenings

• c!is# dust# o.der t!at are roduced fro crus!ing


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Aggregates


– Concrete Sand

• sand t!at !as $een .as!ed to reo%e dust and fines

– Bines

• silt# cla# or dust articles saller t!an 75u usuall

t!e undesira$le iurities in aggregates


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Aggregates


– Noinal Sie

• Not econoical to !a%e 1>> of t!e articles of anaggregate $e .it!in a secified sie range=

• ?educe as uc! reect as ossi$le fro a it in

order to efficientl use t!e aterial resources of a

it• Fsuall 5 ; 1> of t!e aggregate articles can $e

allo.ed to $e larger or saller t!an secs


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Aggregates


– Noinal Sie

• Coarse aggregates 19;4=75 noinal aggregate• Bine aggregate 4=75 noinal aggregate

– Clear

• a single sie coarse aggregate is called clear= @ost

of t!e articles are $et.een t!e secified a:iu

sie and a iniu sie .!ic! is defined as one;

!alf of t!e a:iu

• 19 clear aggregate


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Aggregates• *ggregate -roerties

– ,radation (grain sie analsis)

• grain sie distri$ution for !ig!.a $ases and as!alti:es t!at .ill ro%ide a dense strong i:ture

• ensure t!at t!e %oids $et.een t!e larger articles are

filled .it! ediu articles= !e reaining %oids are

filled .it! still saller articles until t!e sallest %oids

are filled .it! a sall aount of fines=

• Ensure a:iu densit and strengt! using a

a:iu densit cur%e


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Aggregates!eoretical @a:iu Densit Cur%es

• Buller @a:iu Densit Cur%e

- G (d/D)>=5 - G assing sie%e sie Hd" and HD" reresents

t!e a:iu sie%e sie (1>> assing)

• Bederal ig!.a *dinistration

- G (d/D)>=45

– lotted on sei;log aer .!ere sie%e sies are

raised to o.er >=45


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Aggregates


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Aggregate Gradations

• Strengt! or resistance to s!ear failure in road

$ases and a%eents is increased greatl if

t!e i:ture is dense graded


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Aggregate Gradations

a) larger articles are in contact .it! eac! ot!er

de%eloing frictional resistances to s!earing failure=-articles are tig!tl $ond toget!er due to t!e inter;

loc&ing effect of saller articles= !is effect is

!ig!er in (a) t!an ($)


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Aggregate Gradations $) @ust liit t!e aount of fines

– silt and cla articles are relati%el .ea&

– dust on larger aggregates .ill interface .it! t!e

aggregate/as!alt $ond – E:cessi%e fines in a $ase or su$$ase a lead to

drainage on frost lea%ing ro$les

– E:cessi%e fines (saller aggregates) results in .ea&

structures $ecause larger articles are not in contact

.it! eac! ot!er strengt!

– Sn (saller articles) are .ea&er= !erefore anaging

of fines is iortant=


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AggregatesJas!ed Sie%e *nalsis• as a result it is iortant in deterining t!e aount

assing t!e 75µ sie%e

• sale is dried and .as!ed# .as! .ater oured out

o%er t!e 75 u sie%e

• aterial retained is returned to t!e sale for sie%e

analsis

• total aount assing 75 u is e


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AggregatesE:ale 4;1@ass of sale 44=7 g

@ass after .as!ing 414=1 g

?esults of dr sie%ing8

?etained in 4=75 >=>g1=1 +>5=3g

3>> 1+7=9g

75 7=4g

-an 3=g

Bind t!e grain;sie distri$ution80ost in .as!ing o%er 75 G 44=7 g ; 414=1 gG 3+= g

-assing 75 in sie%ing 3= g

otal finer t!an 75 3=4 g


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Aggregates

Note8 Anl >=7 g .as lost during sie%ing# .!ic! is anacceta$le loss=) If a .as!ed sie%e analsis is not

re


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Aggregates

• *ggregate -roerties

– ,radation (grain sie analsis)• ig! densit i:tures are iortant in ters of

densit and as!alt ceent re


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Aggregates• !e relati%e densit (secific gra%it) and

a$sortion of aggregates are iortant

roerties eseciall in as!alt ceenti:tures

– In t!e i: designs# it is iortant to easure

accuratel t!e %olues occuied $ t!e

aggregate and an .ater t!at a !a%e seeedinto t!e ores in t!e articles= !erefore %oids

ust $e considered in t!e aggregate=


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Aggregates

• Bor aggregates

– Dr @ass G @D

– otal @ass G @SSD

• (dr ass @D K a$sor$ed .ater @J*)

– 2ul& Lolue G L2

• (includes %olue of a$sor$ed .ater) – Net Lolue G L N

• L N G L2 ; %olue of a$sor$ed .ater


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Aggregates

• ?elati%e densit calculations are ade

as follo.s8

*arent ?D* G @D/(L N : ρJ)

2ul& ?D2 G @D/(L2 : ρJ)

Saturated# surface;dr ?DSSD G @SSD/(L2 :

ρJ)-ercentage a$sortion *$s G @J*/@D


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Aggregates


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Aggregates

•Saturated Surface Dr – all erea$le ores filled .it! .ater

2ul& Lolue G L NE4 K L*2SA?2ED J*4E?


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Aggregatesis "8.4 g. $e net volume is 8!5.4 cm!. &ind te relative densit' values.

(ass o) a*sor*ed +ater "8.4 , !#.1 - #.! g

olume o) a*sor*ed +ater #.! g - #.! cm!

1 g/cm!

0ul olume 8!5.4 cm! 2 #.! cm! - 8"4.7 cm!

$ere)ore R3 - !#.1 g - ."8

8!5.4 cm! 1 g/cm!

R30 - !#.1 g - .5#

8"4.7 cm! 1 g/cm!

R3SS3 - "8.4 g - ."

8"4.7 cm! 1 g/cm!

% *s - #.! g - 1.!1%

!#.1 g

Example 4-2 $e dr' mass o) a sam6le is !#.1 g. $e mass in saturated sur)ace,


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Aggregates


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Aggregate Properties

• *ggregate ardness (resistant to .ear)

– It is iortant t!at aggregates for a%eent

surfaces not $ecoe rounded or olis!ed t!ere$

reducing s&id resistance

– 0oad ccles in t!e a%eent structure tend to

$rea& aggregates or fines .ill result c!anging t!e

gradation (finer) resulting in reduced strengt! oft!e a%eent structure

– 2ro&en aggregates are not ceented into t!e

structure# again reducing strengt!


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• *ggregate ardness (cont"d)

– ?esistance to degradation during i:ing#

transortation# lacing and coacting is iortant

as soft articles a $rea& c!anging t!e gradation

– 0os *ngeles *$rasion est easures t!e !ardness

of aggregates

– De%al *aratus – *ggregate Iact Lalue est

– -olis!ed Stone Lalue est


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• *ggregate Dura$ilit

– resistance to degradation due to ccles of .etting and

dring# !eating and cooling# and freeing and t!a.ing

– freeing and t!a.ing

• ore saces in t!e aggregate are often saturated and on

freeing e:ands

• reeated ccles can cause t!e aggregate to $rea&

• sedientar roc&s are %ulnera$le $ecause of lanes of

.ea&ness $et.een laers

– Soundness est Bield -erforance / *$sortion Lalue


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• *ggregate -article S!ae/Surface e:ture

– $onding caa$ilit .it! as!alt ceent

• articles .it! roug! fractured faces allo. a $etter $ond

.it! as!alt ceents t!an rounded soot! articles

– resistance to one article sliding o%er anot!er

– flat# t!in# long aggregate articles $rea& easier

t!an cu$ical articles

• Secifications restrict t!e ercentage of long t!in

articles and re


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• Deleterious Su$stances

– !arful or inurious aterials including %arious

tes of .ea& or lo.


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• *ggregate Crus!ing Strengt!

– crus!ing strengt! is t!e coressi%e load t!at

aggregate articles can carr $efore $rea&ing – relati%el uniortant for ost aggregates

strengt! is !ig!er t!an t!e strengt! of an as!alt

i:

• C!eical Sta$ilit

– refers to secific ro$les due to c!eical

coosition


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Highway Materials, Soils, and

Concrete Aggregate Specifications

– Secifications $ !ig!.a deartents ta&es

into account t!e aggregate roerties .e ust

discussed – ?e


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*$rasion test8

Ariginal ass 5>>9g 5>>9;3+7 G 34=

Binal ass 3+7 g 5>>9

Soundness test8

Ariginal ass +49g +49;+115 G +>=+

Binal ass +115 g +49

;lo.er strengt! fines content

;drainage and frost !ea%e otential

;dura$ilit


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Aggregate Sampling and Testing

• !e c!aracteriation of an aggregate source

deends on !o. reresentati%e t!e sales are

ta&en fro t!e aggregates

– sie of sales are secified

– sales s!ould $e o$tained fro t!e final roduct

if ossi$le# after all t!e stes in rocessing andtransortation !a%e $een coleted


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– Sales ta&en fro a roduction or disc!arge

s!ould $e ta&en at %arious ties and across t!e

entire cross section of disc!arge and co$ined to

for one sale

– Saling fro stoc&iles re


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– Sales ta&en fro a truc& or rail.a car s!ould

$e done fro a cross sectional trenc!# t!ree

co$ined to for one sale

– Co$ined sales s!ould $e done .it! e


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– Sales tested in t!e la$ ust $e reresentati%e of

t!e sales deli%ered to t!e la$

• Sale Slitting

– testing aggregates coosed of significant aounts

of $ot! coarse and fine aggregates t!e sale ust

$e slit on t!e 4=75 sie%e and t!e t.o fractions

sie%ed searatel – If not# t!e aount of sale on t!e fine sie%es a

$e too great for effecti%e sie%ing


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Aggregates ENCI579 Lecture4

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