pavement materials aggregates part 1
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Soil Defnition (Engineering)“reers to all unconsolidated
material in the earth’s crust, allmaterial above the bedrock”mineral articles (gravel, sand, silt, cla!)
organic material (to soil, marshes)
"ggregatesmineral articles o a soilsecifcall!, granular soil grougravel, sand, silt
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$ranular Soil $rou ("ggregates)%h!sical &eatheringaction o rost, &ater, &ind, glaciers, lant'animals
articles transorted b! &ind, &ater, icesoils ormed are called granular soil t!e
“grains are similar to the original bedrock”
arger grain sies than cla!s
%articles tend to be more or lesssheres'cubes
*ound &ater is small comared to overallmass
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$ranular Soil $rou ("ggregates)abilit! to achieve greater densities&ell graded granular material
increased soil strengthlo&er ermeabilit!reduced uture settlement
-hese imrovements dictate the useo aggregates in avement la!ers&here &heel loads are greater
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/n combination &ith ashalt cement orortland cement to orm ashalt concreteor cement concrete resectivel!
/n subbases and bases o a road&a!structure
drainage structures
concrete blocks
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-!es o "ggregates
*asic roerties o these aggregates -ests used to evaluate these roerties
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"ggregate Sourcesnatural sand or gravel deosits 2
crushed rock 2
slag and mine reuse
rubble and reuse
artifcial and rocessed materials
ulveried concrete and ashaltavements
other rec!cled and &aste materials
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4atural sand and gravel deositssand and gravel its
sand and gravel soils that have beennaturall! sorted to eliminate most o thesilt or cla! sies then deosited in5glacier ormations (eskers, out&ash lains)
river deositsbeaches o current and revious lakes and seas
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Sand ' $ravel %it DevelomentStriing o tosoil, vegetation7 rom surace
E8cavation o material
material is loose 9 ront end loaders:rushing o the materiallarger sie aggregate is broke do&n to desired sie
crushed gravel is considered high ;ualit! aggregate
&ashing o aggregate cleans dust removes silt'cla! -!e o material deends on bedrock sourceimestone, sandstone,granite,etc<
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:rushed >ock“-!e o aggregates roduced rom
;uarries deends on the t!e o
bedrock”:lasses o >ocks/gneous rocks
Sedimentar! rocks
?etamorhic rocks
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:rushed >ock/gneous >ocks@riginal bedrock ormed rom the cooling o molten
material:oarse grained igneous rock (granite) cooled slo&l!
Aine grained igneous rocks (basalt) cooled raidl!
Sedimentar! >ocksSolidifcation o chemical or mineral sediments
deosited under ancient seasa!ered since original material &as deosited in this
manner
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:rushed >ockSedimentar! >ocksimestone :alcium :arbonate
Dolomite :alcium'?agnesium:arbonate
Shale :la!
Sandstone Buart
:hert Aine sand:onglomerate $ravel
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:rushed >ock?etamorhic >ocks
/gneous or Sedimentar! rocks that have
been metamorhosed due to intense heatand ressureSlate shale
?arble limestone
Buartite sandstone$neiss granite
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:rushed >ock
/gneous and ?etamorhic rocks are ver!
hard and make an e8cellent source or
aggregates
imestone and Dolomite are commonsedimentar! rocks, are soter than igneous
rocks but are accetable or aggregates
Shale rimaril! comosed o cla! grains is&eak and disintegrates easil!
:hert also disintegrates easil!
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Buarr! %it Develoment@ening and Striing o the ace o the
;uarr!
*lasting o rock &ith d!namite into siesthat can be transorted
:rushing o rock into the re;uiredaggregate sies
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Slag and ?ine >euseSlag is a &aste material resulting rom the
treatment o ore to roduce iron, steel, nickel, ubble and >euserec!cling o ulveried concrete rom structuresrec!cled ashalt avements in base courses
rec!cled rubber, crushed glass in base courses
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-!es o "ggregatesAine "ggregateaggregate articles mainl! bet&een the
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-!es o "ggregates:rushed $ravelit gravel (or sand) that has been ut through a
crusher either to break the rounded gravelarticles into smaller sies or to roduce rougher
suraces
:rushed >ockaggregate rom the crushing o bedrock< "ll
articles are angular and not rounded as in gravelScreeningschis, dust, o&der that are roduced rom
crushing
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-!es o "ggregates:oncrete Sandsand that has been &ashed to remove dust
and fnesAinessilt, cla!, or dust articles smaller than
.Cm usuall! the undesirable imurities in
aggregates
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-!es o "ggregates4ominal Sie4ot economical to have 1== o the
articles o an aggregate be &ithin asecifed sie range<
>educing the reection rom a it in order toeFcientl! use the material resources o ait
Gsuall! . 9 1= o the aggregate articlescan be allo&ed to be larger or smaller thansecs
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-!es o "ggregates4ominal Sie:oarse aggregates 169
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"ggregate %roerties$radation (grain sie anal!sis)grain sie distribution or high&a! bases and
bituminous mi8es that &ill rovide a dense strongmi8ture
ensure that the voids bet&een the larger articlesare flled &ith medium articles< -he remaining voidsare flled &ith still smaller articles until the smallestvoids are flled &ith a small amount o fnes<
Ensure ma8imum densit! and strength using ama8imum densit! curve
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-heoretical ?a8imum Densit! :urvesAuller ?a8imum Densit! :urve
% H (d'D)=
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Strength or resistance to shear ailurein road bases and avements is
increased greatl! i the mi8ture isdense graded
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a) larger articles are in contact &ith eachother develoing rictional resistances toshearing ailure< %articles are tightl! bondtogether due to the inter9locking eKect osmaller articles< -his eKect is higher in (a)than (b)
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b) ?ust limit the amount o fnessilt and cla! articles are relativel! &eakdust on larger aggregates &ill interace
&ith the aggregate'bituminous bondE8cessive fnes in a base or subbase ma!
lead to drainage on rost heaving roblemsE8cessive fnes (smaller aggregates) results
in &eak structures because larger articles
are not in contact &ith each other strength Sn (smaller articles) are &eaker< -hereore managing o fnes is imortant<
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Lashed Sieve "nal!sisas a result it is imortant in determining the
amount assing the .µm sieve
samle is dried and &ashed, &ash &ater ouredout over the . µm sieve
material retained is returned to the samle orsieve anal!sis
total amount assing . µm is e;ual to the amount
lost in &ashing and assing . µm sieve
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E8amle 91 ?ass o samle 0etained in
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4ote5 @nl! =
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"ggregate %roerties$radation (grain sie anal!sis)Jigh densit! mi8tures are imortant in terms o
densit! and ashalt cement re;uired< "shalt mustcoat each article and fll in most o the void sace</ !ou fll in void sace &ith cheaer material suchas aggregates !ou save ashalt
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