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    Concrete Technology

    Dr. P. DINAKAR

    Department of Civil Engineering

    Concrete Aggregates

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    Factors influencing concrete structure

    performance

    Aggregates

    Type

    Grading

    Cement

    Type

    Fineness

    Water

    Quality

    Cllimit! etc"

    AdmixturesType

    Interaction#prop"

    Materials

    Mix design

    $roportions

    Cement %uality

    C

    'a(imum water

    )dmi(tures

    Mixing

    Fresh concrete

    Concrete

    Element design

    Insitu

    $recast

    uilding !ractice

    Formwor*Tolerances

    +einforcing

    Placing

    Com!action

    Construction

    Curing

    Engineering

    Design

    Details

    +einforcement

    Crac* control

    cover

    Design

    Architectural

    Design

    Details

    ,ection#dimension

    ,urface finishes

    En"ironmental

    in#luences

    Com!leted

    element

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    )ggregates

    )ggregates are defined as inert! granular! and inorganic

    materials that normally consist of stone or stoneli*esolids"

    )ppro(imately threefourths of the volume of

    conventional concrete is occupied by aggregate"

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    Classification of )ggregates

    According to &ource'

    -" .atural aggregate/ .ative deposits with no change intheir natural state other than washing! crushing 0

    grading" 1sand! gravel! crush stone2

    3" )rtificial aggregates/ They are obtained either as a by

    product or by a special manufacturing process such asheating" 1blast furnace slag! e(panded perlite2

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    Classification of )ggregates

    4ltra 5ight weight/ 4& 6 788*g#m9

    Corresponding concrete 4& : -388*g#m9

    For non structural member only

    5ight weight/ 788*g# m96 4& 6 --38*g#m9

    Corresponding concrete 4& 6 -;88*g#m9

    Can be used as structural member

    .ormal weight/ 4& : -738

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    Classification of )ggregates

    Weight categories *sesIndicati"e concrete

    densit+ ,-gm$

    /4ltra lightweight density 6788 *g#m9

    Thermalinsulation

    788 to -888

    5ightweight density 63-88 *g#m9

    5ightweightstructuralconcretes

    -88 to -;88

    .ormalweight density @3-88 *g#m9

    .ormalweightstructuralconcretes

    3888 to 3=88

    ?eavyweight density @9388 *g#m9

    ?eavyweightconcrete

    +adiationshielding

    9888 to 7888

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    Classification of )ggregates

    According to Petrological Characteristics'

    -" Igneous roc*s/ are formed by solidification of moltenlava" 1granite2

    3" ,edimentary roc*s/ are obtained by deposition of

    weathered 0 transported pree(isting roc*s or solutions"

    1limestone2

    9" 'etamorphic roc*s/ are formed under high heat 0

    pressure alteration of either igneous 0 sedimentary

    roc*s 1marble2"

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    Classification of )ggregates

    In accordance ith &i3e

    Coarse aggregate/ ,ie @ >"7mm

    Fine aggregate 1sand2/ ,ie from 7 micron m to>"7mm

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    ,ampling

    Tests in the lab is carried out on the samples" ,o!

    certain precautions in obtaining a sample must be ta*ento obtain representative sample"

    The main sample is made up of portions drawn from

    different points" The minimum number of portions!

    increment! is -8 0 they should add up to a weight not

    less than/

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    ,ampling

    Max. Particle

    &i3e ,mm/

    Min. Weight o#

    &am!le ,-g/@ 37 mm 78

    37 < 7 mm 37

    6 7 mm -9

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    'ethods of reducing the amount of sample7uartering'

    'i( the field sample over three times on a level surface"

    ,hovel the sample to a conical shape"

    $ress the ape( 0 flatten the conical shape"

    Divide them into four e%ual %uarters"

    Discard two diagonally opposite %uarters 0 use the remainder" If this remainder is still too large follow the same path"

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    $article ,hape and ,urface Te(ture

    In addition to petrological character! the e(ternal

    characteristics! i"e" The shape 0 surface te(ture ofaggregates are of importance"

    Particle &ha!e

    +ounded/ Completely water worn 0 fully shaped byattrition" 1+iver Gravel2

    Irregular/ $artly shaped by attrition so it contains some

    rounded edges" 15and Gravel2

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    $article ,hape and ,urface Te(ture

    Angular/ ?as sharp corners! show little evidence of

    wear" 1Crushed ,tone2

    Fla-+/ Thic*ness is relatively small with respect to two

    other dimensions" 15aminated +oc*s2

    Elongated/ ?ave lengths considerably larger than twoother dimensions

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    $article ,hape and ,urface Te(ture

    Flat and elongated particles should be limited to about -7

    percent by weight of the total aggregate

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    $article ,hape and ,urface Te(ture

    +ounded aggregates are suitable to use in concrete

    because fla*y 0 elongated particles reduce wor*ability!increase water demand 0 reduce strength"

    In the case of angular particles! the bond between agg"

    particles is higher due to interloc*ing but due to highersurface area! angular particles increase water demand

    0 therefore reduces wor*ability" As a result8 #or the

    same cement content 9 same or-a:ilit+8 rounded

    agg. ;i"e higher strength.

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    $article ,hape and ,urface Te(ture

    ,urface Te(ture

    This affects the bond to the cement paste 0 also

    influences the water demand of the mi("

    ,mooth/ Bond b#w cement paste 0 agg is wea*"

    +ough/ Bond b#w cement paste 0 agg" is strong"

    ,urface te(ture is not a very important property from

    compressive strength point of view but aggregates

    having rough surface te(ture perform better under

    fle(ural 0 tensile stresses"

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    $article ,hape and ,urface Te(ture

    &mooth Rough

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    ,hape of the )ggregate and its Effects

    +oundness

    &!hericit+

    >>>

    &ie"e &ha-er ?ateral 9 @ertical Motion

    6.5(6 mm

    %.0( mm

    2.$) mm

    5.51 mm

    6.)66 mm

    6.$66 mm

    Pan

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    Grading of )ggregates

    The particle sie distribution in an aggregate sample is

    *nown as gradation" ,trength development of concrete depends on degree

    of compaction 0 wor*ability together with many other

    factors" ,o! a satisfactory concrete should be

    compacted to ma( density with a reasonable wor*"

    An the other hand! in good concrete all aggregate

    particles must be covered by cement paste"

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    Grading of )ggregates

    The grading of aggregate must be so that the

    wor*ability! density 0 volume stability of concrete maynot be adversely affected by it"

    Fine $articles Khigher cost

    Coarse $articlesKless wor*ability

    ) reasonable combination of fine 0 coarse aggregate

    must be used" This can be e(pressed by ma(imum

    density or minimum voids concept"

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    Grading of )ggregates

    ) cube with a dimension of 3D(3D(3D is

    filled with spheres of diameter D

    LcubeM13D29M;D9

    -LsphereM1>#92N1D#329O8"73D9

    ;PLspM;P8"73D9O>"3D91solid volume2

    Loid LolumeM;D9>"3D9M9";D9

    3D

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    Grading of )ggregates

    ,ame cube filled with spheres of diameter D#>"

    ,olid LolumeM;P;P;P1>#92N1D#;29O>"3D9

    Loid LolumeO9";D9

    ,ie of agg" is not important" If an agg" with the same

    sie is used amount of void volume will not change" ,o!

    to overcome this different sies of particles should beused"

    ?owever! you should not forget that as aggregate get

    finer! the surface area increases"

    'ore surface area Kmore paste 0 water re%uirement

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    Compact )ggregate ,*eleton

    Fuller Grading 93 mm

    CM 988 *g#m R &M-=3 *g#m

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    5oose )ggregate ,*eleton

    ',) -J mm

    CM >-8 *g#m R &M-;J *g#m

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    +eduction of Loids

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    Factors )ffecting a Desired Grading

    ,urface area of the )ggregate

    The lower the surface area! the lesser is the pastere%uirement"

    +elative Lolume of )gg" in Concrete

    ?igher volume of agg"/ Keconomical

    Khigher strength! higher volume stability

    Kless wor*ability S

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    Factors )ffecting a Desired Grading

    &or*ability/The ease with which a concrete mi(ture can be

    mi(ed! transported! placed in the form 0 compacted without

    any segregation" &or*ability increases as the amount of

    paste b#w fine agg" part increases" It also increases as the

    amount of mortar b#w coarse agg" $articles increases"

    ,egregation/,eperation of the particles with different sies

    0 specific gravities" The re%uirements of wor*ability and

    absence of segregation tend to oppose each other" Thus!

    these two factors are interrelated" The maor of these is

    wor*ability which! in turn! affects most of the properties of

    concrete"

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    Determination of the Grading of )ggregate

    There are two different methods for determining the

    aggregate grading/ Fineness 'odulus 1F'2

    Granulometry

    The grading of the particles in an agg" sample is

    performed by sieve analysis" The sieve analysis is

    conducted by the use of standard test sieves" Test

    sieves have s%uare openings 0 their designation

    correspond to the sies of those openings"

    D t i ti f th G di f ) t

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    Determination of the Grading of )ggregate

    Fineness Modulus ,FM/'

    F' is a single figure which is the sum of cumulative

    retained on a series of sieves having a clear opening half

    that of the preceding one" 4sually determined for fine

    aggregate

    For Fine )gg"KU>! U;! U-=! U98! U78! U-88 practicallimitsK39"7V

    For Coarse )gg"K1Fine set W 9#; W 9#> W- XW 9 2

    practical limitsK7"7;"8V The F' of the mi(ture of two or more agg" is the weighted

    average of the F' of that two more agg"

    D t i ti f th G di f ) t

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    Determination of the Grading of )ggregate

    $an is not included"Anly standard sieves are included! if we were given U-8

    sieve you should not use that in calculations

    D t i ti f th G di f ) t

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    Determination of the Grading of )ggregate

    Fi ' d l f Bl d d ) t

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    Fineness 'odulus for Blended )ggregate

    Determination of the Grading of )ggregate

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    Determination of the Grading of )ggregate

    The fine aggregate with the F'M9"37 and the coarse

    aggregate with the F'M";7 are available" Combine

    them in such a way that the F' becomes =";

    Y / Lolume of Fine aggregate

    9"37YW";71-88Y2 M =";

    -88

    Therefore Y M 39

    39 of fine aggregate and of coarse aggregate

    should be mi(ed

    Determination of the Grading of )ggregate

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    Determination of the Grading of )ggregate

    ;ranulometr+'

    The F' is not always representative of the gradation ofan aggregate sample and various gradation curves may

    give the same F'"

    In the gradation curves! the vertical a(is represents the

    passing 0 the horiontal a(is represents the sieveopening"

    ) logarithmic scale is used for horiontal a(is

    Determination of the Grading of )ggregate

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    Determination of the Grading of )ggregate

    ) good aggregate gradation for a particular concreteis the one that leads to a wor*able! dense 0 uniform

    concrete! without any segregation of particles"

    DI. Grading 5imits for ',) 37 mm

    1adapted to ),T' sieves2

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    6.5(6.$

    6.)5.2

    2.%%.1

    4.)52.(

    542(

    6

    56

    26

    $6

    %6

    (6

    )6

    06

    16

    46

    566

    &ie"e A!ening ,mm/

    BP

    assing

    A

    C

    tooco

    arse

    o!tim

    um

    too#ine

    1adapted to ),T' sieves2

    Water

    dema

    nd

    acc

    e!ta:le

    Com:ined Aggregate ;rading

    Fuller Curve

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    Fuller Curve

    Determination of the Grading of )ggregate

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    Determination of the Grading of )ggregate

    There is no single ideal grading curve Instead!

    standards provide upper 0 lower limits"

    ),T' +e%uirements for F) 0 C)

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    ),T' +e%uirements for F) 0 C)

    Types of Gradation

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    Types of Gradation

    Types of Gradation

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    Types of Gradation

    In uniform grading all particles are of the same sie"

    .ote that this produces a large volume of voidsirrespective of particle sie" ?ence the paste

    re%uirement for this concrete is high"

    Continuous grading incorporates a combination of

    particles of many sies" ?ence it minimies the volume

    of voids but increases the particle surface area" This is

    the preferred gradation"

    Gap gradation involves grading in which one or more

    sies are omitted" This type of concrete is used

    generally for architectural or aesthetics purpose"

    ,pecific Gravity

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    ,pecific Gravity

    ,pecific gravity is the ratio of the weight of a unit volume

    of material to the &eight of the same volume of water at

    38Z to 37ZC"

    ,pecific Gravity of )ggregates

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    p y gg g

    ,p"Gr" is used in certain computations for concrete mi(

    design or control wor*! such as! absolute volume of

    aggregate in concrete" It is not a measure of the %uality of

    aggregate"

    Lolume of )ggregate [

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    gg g

    'oisture Condition of )ggregates

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    gg g

    'oisture Condition of )ggregates

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    gg g

    'oisture Condition of )ggregates

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    gg g The moisture condition of aggregates refers to the presence of water in the pores

    and on the surface of aggregates" There are four different moisture conditions/

    "en Dr+ ,D/'This condition is obtained by *eeping aggregates at

    temperature of --88C for a period of time long enough to reach a constant

    weight"

    Air Dr+ ,AD/'This condition is obtained by *eeping aggregates under room

    temperature and humidity" $ores inside the aggregate are partly filled with water"

    &aturated &ur#ace Dr+ ,&&D/'In this situation the pores of the aggregate are

    fully filled with water and the surface is dry" This condition can be obtained by

    immersion in water for 3> hours following by drying of the surface with wet cloth"

    Wet ,W/'The pores of the aggregate are fully filled with water and the surface of

    aggregate is covered with a film of water"

    'oisture Content 1'C2 Calculations

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    'oisture Content 1'C2 Calculations

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    'oisture Content 1'C2 Calculations

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    Density and ,pecific Gravity

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    Density and ,pecific Gravity

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    Density and ,pecific Gravity

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    Determination of ,pecific Gravity of )ggregates

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    Archimedes Princi!le

    Coarse )ggregate )ggregates are oven dried at -87\7]C overnight 0 the

    weight is measured as 1)2Koven dry weight

    )ggregates are soa*ed in water for 3> hours" )ggs are

    ta*en out from water 0 rolled in a large absorbent cloth!

    until all visible films of water are removed 0 then

    weighed 1B2Ksaturated surface dry weight

    )ggregates are then weighed in water 1C2

    Determination of ,pecific Gravity of )ggregates

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    Determination of ,pecific Gravity of )ggregates

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    Fine Aggregate

    )ggregate are oven dried to constant weight at

    -87\7]C" 'easure the dry weight as 1)2

    ,oa* them in water for 3>hrs

    ,tir the sample to bring it to ,,D condition" 4se the

    Cone Test for ,urface 'oisture Determination 1&eightas ,2

    Fill the aggs in ,,D condition into a pycnometer 1to a

    calibrated level2 and weight it!

    1waterWpyconometerWagg2 1C2

    Fill the pyconometer with water only 1to a calibrated

    level2 and weight it 1waterWpyconometer2 1B2

    ,pecific Gravity Test for ,and

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    Determination of ,pecific Gravity of )ggregates

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    'oisture Condition of )ggregates

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    ,ignificance of 'oisture Determination

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    ,,D Condition KE%uilibrium for 'ositure Condition

    If total moisture content M 8 K)gg" is bonedry 1oven

    dry2

    If total moisture content 6 absorption capacityK It can

    absorb water

    If total moisture content @ absorption capacityK Thereis free water on the surface of agg"

    'i( Design Calculations are Based on )ggs in ,,D

    Condition" Therefore! for aggs not being in that condition

    corrections have to be made w#c ratioKw should be free water

    E(amples

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    The oven dry mass of a sample of aggregate is -J;3

    gm" The mass in a saturated surface dry condition is

    388=" gm" The net or solid volume of the aggregates

    is 9>"> cm9" Find the apparent specific gravity! the bul*

    specific gravity and the percentage absorption"

    'a( )ggregate ,ie

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    It^s the smallest sieve sie through which the entire

    amount of the agg particles can pass"

    The larger the sie of agg! the smaller the surface area

    to be wetted per unit weight" Thus! e(tending the

    grading of agg to a larger ma( sie lowers the water

    re%uirement of the mi(" ,o! for the same wor*ability 0

    cement content higher strength will be obtained"

    'a( )ggregate ,ie

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    Aptimum ma( agg sie for structural concrete is 37mm"

    ,tudies have shown that concrete^s made with ma( aggsie greater than >8mm have lower strength" Because

    of the smaller surface area for the bond between agg to

    paste" Lolume changes in the paste causes larger

    stresses at the interface"

    ,tandard 5imitations for 'a( )ggregate ,ie

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    The concrete mi( must be so that! it can be placed

    inside the molds and between the reinforcing bars easily

    without any segregation" ,o! ma( agg sie 1Dma(2 should

    not e(ceed/

    -2 -#7 of the narrowest dimension of the mold"

    ,tandard 5imitations for 'a( )ggregate ,ie

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    -#9 of the depth of the slab

    _ of the clear spacing between reinforcement

    Dma(6 >8mm

    5imitations for 'a( )ggregate ,ie

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