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Transcript of Aggregates 1st
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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"
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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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