AGGREGATESAGGREGATES

StrengthStrength

Dimension Dimension stabilitystability

EconomyEconomy

ObjectivesObjectives

Understand:Understand:

Types of aggregatesTypes of aggregates

Characteristics and properties of Characteristics and properties of aggregatesaggregates

Test of aggregatesTest of aggregates

AggregatesAggregates

A rocklike material of A rocklike material of various sizes and shapes various sizes and shapes used in the manufacture used in the manufacture of concreteof concrete

ASTM defines ASTM defines aggregates aggregates as granular material such as granular material such as sand, gravel, crushed as sand, gravel, crushed stone used with stone used with cementing medium to cementing medium to form mortar or concreteform mortar or concrete

AggregatesAggregates

NaturalNatural – taken from – taken from natural deposits natural deposits without change in without change in their nature during their nature during productionproduction

ManufacturedManufactured – – include blastfurnace include blastfurnace slag, clay, slag, clay, lightweight lightweight aggregateaggregate

AggregatesAggregates

CoarseCoarse

CrushedCrushed

UncrushedUncrushed

FineFine

CrushedCrushed

UncrushedUncrushed

Based on sizesBased on sizes

Fine aggregate – Fine aggregate – less than 5 mm (C, less than 5 mm (C, M, F)M, F)

Coarse aggregate – Coarse aggregate – greater than 5 mm ( 10, greater than 5 mm ( 10, 20, 40 mm)20, 40 mm)

AggregatesAggregates

CrushedCrushed – – sharp angular sharp angular particles, from particles, from quarry, rough quarry, rough surface, good surface, good bond strength, bond strength, low workabilitylow workability

UncrushedUncrushed

Uncrushed Uncrushed – round shapes, smooth – round shapes, smooth surface, from river, low bonding surface, from river, low bonding properties, high workabilityproperties, high workability

Types of rock Types of rock

Granite – Granite – hard, tough and hard, tough and densedense

Sandstone – Sandstone – may contain claymay contain clay

Limestone – Limestone – may contain claymay contain clay

Types of aggregates based on Types of aggregates based on specific gravityspecific gravity

LightweightLightweight aggregate aggregate

Normal weightNormal weight aggregate aggregate

HeavyweightHeavyweight aggregate aggregate

Lightweight AggregateLightweight Aggregate

Bulk density less than 1200 kg/mBulk density less than 1200 kg/m33

Used in manufacturing lightweight Used in manufacturing lightweight concrete, lightweight masonry blockconcrete, lightweight masonry block

Porous, good thermal insulationPorous, good thermal insulation

Natural lightweight aggregate consists Natural lightweight aggregate consists of particles derived from natural rocks, of particles derived from natural rocks, primarily those of natural volcanic primarily those of natural volcanic originorigin

Cont.Cont.

Manufactured lightweight Manufactured lightweight aggregateaggregate – is produced by – is produced by expanding some raw materials in expanding some raw materials in a rotary kiln, on a sintering grate, a rotary kiln, on a sintering grate, or by mixing them with wateror by mixing them with water

Normal Weight AggregateNormal Weight Aggregate

Density in the range of 2300 – 2500 Density in the range of 2300 – 2500 kg/mkg/m33

Mostly obtained from quarry, riverMostly obtained from quarry, river

Specific gravity in the range of 2.5-3.0Specific gravity in the range of 2.5-3.0

Suitable for most constructionsSuitable for most constructions

Need to be cleaned from impuritiesNeed to be cleaned from impurities

Chloride content should be less than Chloride content should be less than 1%1%

Heavyweight AggregateHeavyweight Aggregate

Density in the range of 4000 – 8500 Density in the range of 4000 – 8500 kg/mkg/m33

Used primarily to manufacture Used primarily to manufacture heavyweight concrete for protection heavyweight concrete for protection against nuclear radiationagainst nuclear radiation

Low workabilityLow workability

Eg. Barite with specific gravity of 4.5Eg. Barite with specific gravity of 4.5

Properties of AggregatesProperties of Aggregates

A number of A number of physical and mechanicalphysical and mechanical properties affect properties affect durabilitydurability, , strengthstrength, , and performance of construction and performance of construction products manufactured using products manufactured using aggregatesaggregates

The The aggregate particles should retainaggregate particles should retain their strength, shape, and texture when their strength, shape, and texture when used with materials such as cementused with materials such as cement

Properties of AggregatesProperties of Aggregates

Compressive strengthCompressive strengthSpecific gravitySpecific gravityBulk densityBulk densityPorosityPorosityVoidsVoidsAbsorptionAbsorption

Modulus of elasticityModulus of elasticity

Moisture contentMoisture content

ShrinkageShrinkage

Grading and finenessGrading and fineness

Chemical reactivityChemical reactivity

Specific GravitySpecific Gravity

The ratio of the mass of a unit volume The ratio of the mass of a unit volume of a material at a specific temperature of a material at a specific temperature to the mass of the same volume of gas-to the mass of the same volume of gas-free distilled water at that temperaturefree distilled water at that temperatureThe weight of aggregate particles The weight of aggregate particles depend on the moisture level.depend on the moisture level. The The specific gravity readings should be specific gravity readings should be associated with the moisture level or associated with the moisture level or moisture content measurementmoisture content measurement

ExampleExampleAggregateAggregate TypeType Specific GravitySpecific Gravity

GraniteGranite Normal weightNormal weight 2.652.65

GravelGravel Normal weightNormal weight 2.702.70

SandSand Normal weightNormal weight 2.602.60

ScoriaScoria LightweightLightweight 0.750.75

PumicePumice LightweightLightweight 0.750.75

HematiteHematite HeavyweightHeavyweight 5.005.00

BariteBarite HeavyweightHeavyweight 4.504.50

Moisture ContentMoisture Content

Two types of moisture:Two types of moisture:

AbsorbedAbsorbed moisture moisture

SurfaceSurface moisture moisture

Absorbed MoistureAbsorbed Moisture

The The weight of water absorbedweight of water absorbed by dry aggregate by dry aggregate particles in reaching the particles in reaching the saturated surface dry saturated surface dry condition.condition.

Usually expressed as a percentage of dry weightUsually expressed as a percentage of dry weight

In this state there is In this state there is no water on the surface of a no water on the surface of a particle, but all the pores are filled with waterparticle, but all the pores are filled with water

A particle will A particle will neither absorbneither absorb moisture from moisture from nor nor contributecontribute moisture to the surrounding moisture to the surrounding

Surface MoistureSurface Moisture

The moisture that is The moisture that is in in excessexcess of absorbed of absorbed moisturemoisture

Level of AbsorptionLevel of Absorption

Granite – Granite – less than 1%less than 1%

Porous sandstone – Porous sandstone – as high as as high as 13%13%

Lightweight aggregate – Lightweight aggregate – in the in the range of 5 – 20%range of 5 – 20%

Moisture Condition of AggregatesMoisture Condition of Aggregates

Oven dryOven dry

Air dryAir dry

Surface Surface Saturated DrySaturated Dry

WetWet

Effect Moisture ContentEffect Moisture Content

MoistureMoisture DesignDesign

(kg)(kg)

AbsorbedAbsorbed

(kg)(kg)

AdditionalAdditional

(kg)(kg)

ActualActual

(kg)(kg)

WorkabilityWorkability Strength/Strength/

DurabilityDurability

Oven-Oven-DryDry

1010 22 00 88 DecreaseDecrease IncreaseIncrease

Air-DryAir-Dry 1010 11 00 99 DecreaseDecrease IncreaseIncrease

SSDSSD 1010 00 00 1010 RequiredRequired RequiredRequired

WetWet 1010 00 22 1212 IncreaseIncrease DecreaseDecrease

Oven-DryOven-Dry

Is obtained when Is obtained when all the moisture is all the moisture is driven outdriven out of the pores by drying the of the pores by drying the aggregate to a constant weight at aggregate to a constant weight at temperature of about temperature of about 110 °C110 °CWhen mixing water is introduce into the When mixing water is introduce into the concrete mix concrete mix part of itpart of it will be absorbed will be absorbed by the aggregate resulting to by the aggregate resulting to less waterless water for for hydration processhydration process and and workabilityworkability of concreteof concrete

Air-DryAir-Dry

Is the condition when the Is the condition when the amount of amount of moisture in the particles is less thanmoisture in the particles is less than that that of the of the saturated surface drysaturated surface dry condition condition but more than which remains in oven dry but more than which remains in oven dry conditioncondition

Part ofPart of the mixing water will be absorbed the mixing water will be absorbed by the aggregate during mixing of by the aggregate during mixing of concreteconcrete

Surface Saturated DrySurface Saturated Dry

When When all pores in the particles are filled all pores in the particles are filled with waterwith water but no moisture exists on but no moisture exists on the outside surfacethe outside surface

The mixing The mixing water will be used water will be used totallytotally for for the hydration process and workability the hydration process and workability of concreteof concrete

WetWet

When When excess moistureexcess moisture ( (free water or free water or surface moisturesurface moisture) remains on the ) remains on the surface of particles, as in sand exposed surface of particles, as in sand exposed to rainwaterto rainwater

There There will be extra waterwill be extra water in the concrete in the concrete mix which will affect the compressive mix which will affect the compressive strengthstrength

How Level of Moisture AffectHow Level of Moisture Affect

WorkabilityWorkability

StrengthStrength

DurabilityDurability

ExampleExample

Determine the Determine the moisture contentmoisture content, , absorptionabsorption, and , and free moisture free moisture contentcontent of the fine aggregate of the fine aggregate sample.sample.

Initial sample weight = 1.2 kgInitial sample weight = 1.2 kg

Saturated surface dry weight = 1.14 kgSaturated surface dry weight = 1.14 kg

Oven-dry weight = 1.06 kgOven-dry weight = 1.06 kg

Moisture ContentMoisture Content

Moisture content = Moisture content = (Initial sample wt – (Initial sample wt – Oven-dry wt)Oven-dry wt) / / (Oven-dry wt) * (Oven-dry wt) *

100100

= (1.2 – 1.06) / 1.06*100= (1.2 – 1.06) / 1.06*100

= 13.2%= 13.2%

AbsorptionAbsorption

Absorption = Absorption = (SSD wt – Oven-dry wt)(SSD wt – Oven-dry wt) / / Oven-dry wt * 100Oven-dry wt * 100

= (1.14 – 1.06) / 1.06*100= (1.14 – 1.06) / 1.06*100

= 7.5% = 7.5%

Free MoistureFree Moisture

Free Moisture = Free Moisture = Moisture contentMoisture content – – AbsorptionAbsorption

= 13.2 – 7.5= 13.2 – 7.5

= 5.7%= 5.7%

BUKL DENSITY OF AGGREGATEBUKL DENSITY OF AGGREGATE

Bulk densityBulk density

Known as unit weight or dry-rodded Known as unit weight or dry-rodded weightweight

The mass per unit volume of The mass per unit volume of aggregate aggregate

The mass is determined in dry The mass is determined in dry condition and the volume includes condition and the volume includes the volume of voidsthe volume of voids

VoidVoid

Represent the Represent the amount of air spaceamount of air space in in the aggregate or space between the the aggregate or space between the particlesparticles

Void content is generally Void content is generally expressed expressed as percentas percent of gross volume which is of gross volume which is solid volume plus volume of voidssolid volume plus volume of voids

PorosityPorosity

Is defined as the ratio of the Is defined as the ratio of the volume volume of the poresof the pores in a particle to its in a particle to its total total volume of solidvolume of solid volume plus the volume plus the pore volumepore volume

How it affects strength and durability?How it affects strength and durability?

Modulus of ElasticityModulus of Elasticity

Defined as the ratio of stress to Defined as the ratio of stress to corresponding strain below the corresponding strain below the proportional limitproportional limit

The modulus of elasticity of concrete The modulus of elasticity of concrete increases with increase in the modulus increases with increase in the modulus of aggregateof aggregate

Creep and shrinkageCreep and shrinkage of concrete also of concrete also affected by the modulus of elasticity of affected by the modulus of elasticity of aggregateaggregate

Compressive StrengthCompressive Strength

Compressive strength of aggregate Compressive strength of aggregate depends on the depends on the compressive compressive strength of the original rockstrength of the original rock

It will affect the It will affect the compressive compressive strength of concretestrength of concrete

Gradation/GradingGradation/Grading

Gradation refers Gradation refers to the to the proportions proportions of aggregate of aggregate distributeddistributed in in specified particle-specified particle-size rangesize range

Important property Important property that that affectsaffects mix mix proportions, proportions, workability, economy, workability, economy, porosity, durability porosity, durability and shrinkageand shrinkage of the of the finish productfinish product

GradingGrading

Refers to Refers to the the processprocess that that determines the determines the particle size particle size distribution of a distribution of a representative representative sample of the sample of the aggregateaggregate

Sieve analysisSieve analysis – – the process of the process of dividing a sample dividing a sample of aggregate into of aggregate into fractions of same fractions of same particle sizeparticle size

GradedGraded

Normally graded aggregate – Normally graded aggregate – conforms conforms to the grading limitsto the grading limits

Dense-graded aggregate – Dense-graded aggregate – particle-size particle-size distribution with least voids distribution with least voids

Open-graded aggregate – Open-graded aggregate – particle-size particle-size distribution with many voidsdistribution with many voids

Gap-graded aggregate – Gap-graded aggregate – one or more one or more intermediate sizes are missingintermediate sizes are missing

Sieve ApparatusSieve Apparatus

Larger to smaller Larger to smaller sizessizes

Square openingSquare opening

10 minutes10 minutes

Weigh the Weigh the aggregate retainaggregate retain

SIEVE

SHAKER

Grading limits (BS 882:1983)Grading limits (BS 882:1983)

Sieve Sieve sizesize

Overall Overall limitslimits

Coarse Coarse (C)(C)

Medium Medium (M)(M)

Fine (F)Fine (F)

5 mm5 mm 89-10089-100 -- -- --

2.362.36 60-10060-100 60-10060-100 65-10065-100 80-10080-100

1.181.18 30-10030-100 30-9030-90 45-10045-100 70-10070-100

600 um600 um 15-10015-100 15-5415-54 25-8025-80 55-10055-100

200200 5-705-70 5-405-40 5-485-48 5-705-70

150150 0-150-15 -- -- --

ExampleExample

Sieve sizeSieve size Mass Mass retained retained (g)(g)

Percentage Percentage retained (%)retained (%)

Percentage Percentage cumulative cumulative passing (%)passing (%)

Grading Grading (compare, M)(compare, M)

10.0 mm10.0 mm 00 00 100100

5.005.00 66 22 9898 --

2.362.36 3131 1010 8888 65-10065-100

1.181.18 3030 1010 7878 45-10045-100

600 um600 um 5959 1919 5959 25-8025-80

300300 107107 3535 2424 5-485-48

150150 5353 1717 77 --

Less 150Less 150 2121 77 00

TOTALTOTAL 307307

Particle Size DistributionParticle Size Distribution

Effect Of GradationEffect Of Gradation

Strength and Durability

CorrosionCorrosion

How do this occur?

ArigatoArigato

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