Inert or chemically inactive materials which when bonded together with cement forms concrete DEFINITION 70 to 80 of concrete is composed of aggregates Properties of aggregates affect properties of concrete ID: 204494
Download Presentation The PPT/PDF document "AGGREGATES" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
AGGREGATESSlide2
Inert or chemically inactive materials which when bonded together with cement forms concrete
DEFINITION:Slide3
70% to 80% of concrete is composed of aggregatesProperties of aggregates affect properties of concrete.
Avoids cracking and gives strength to concrete.Eg
: natural sand, gravel, crushed stone etc.Slide4
According to nature of formation
Natural aggregates
Artificial aggregates
According to size
Coarse aggregates
Fine aggregates
All-in aggregates
According to shape
Rounded aggregatesIrregular or partially rounded aggregatesFlaky aggregatesAngular aggregatesElongated aggregates
CLASSIFICATIONSlide5
According to nature of formation
Natural aggregates:
obtained from natural sourcesSlide6
A
rtificial aggregates:
manufactured from raw materials by fusing in rotary kilnSlide7
A
ccording to size:
Coarse aggregates:
retained on 4.75mm sieve.
max. size for plain concrete – 150mm
max. size for reinforced concrete – 60mm or lessSlide8
Coarse aggregates:
Graded aggregates
Single sized aggregatesSlide9
F
ine aggregates:
passing through 4.75mm seive and retained on 0.15mm sieve.Slide10
F
ine aggregates:
Natural sand
Crushed stone sand
Broken brick fine aggregateSlide11
All – in aggregates
Comes from pit or river bed
Used without seperating into different sizes.
Contains fine and coarse aggregates
Used for unimportant worksSlide12
Rounded aggregates:
Surface area minimumConcrete requires lesser cement – low strength
According to shapeSlide13
I
rregular aggregates:
natural irregularity due to attrition with rounded edgesSlide14
F
laky aggregates:
usually angular – thickness is small relative to other dimensionsSlide15
A
ngular aggregates:- well defined edges
- concrete – more cement – high strength and durabilitySlide16
E
longated aggregates:
length is considerably greater than other two dimensionsconcrete – poor quality and less durable.Slide17
Pit SandRiver Sand
Sea Sand
Sources of aggregates:Slide18
P
it Sand:pits dug at a depth of 1.5m to 2m in soil
sharp, angular porous and free from harmful chemicalsfor making mortarSlide19
R
iver Sand:obtained from river beds and banks
bright and clear – sharp or roundedfor mortar and plasteringSlide20
S
ea Sand:seashores
brown and roundedcontains salts – not used for constructionSlide21
M
anufactured Sand:
manufactured in stone crushersless impuritiesbetter control over size and qualitySlide22
Hard, strong, durable
Should not react with cement or steelAngular and rough surfaceFree from organic substances
Contains stone gravels and sand or in various combinations
R
equirements:Slide23
Representation of particle size in a sample of aggregatesGood grading – all standard sizes in required proportions
Sieve analysis – determination of proportions of particles in an aggregate by seperation
on sievesG
rading of aggregatesSlide24
80 mm40 mm
20 mm10 mm4.75 mm2.36 mm
1.18 mm600 microns300 microns150 microns
pan
S
ieve analysisSlide25
S
ieve analysisSlide26
Weight of residue on each sieve% weight retainedCummulative
% weight retainedFineness modulus =
WR – sum of cummulative % retainedSlide27
Sands are classified as:
type
Fineness modulus
Fine sand
2.2 to
2.6
Medium sand
2.6
to 2.9Coarse sand2.9 to 3.2Slide28
B
ased on gradation
well graded – good representation of all sizesSlide29
P
oorly graded:excess of of certain sizesSlide30
G
ap graded:one or intermediate sizes are missing