Relative Density and Absorption

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Important Properties

Hardness (resistance to wear)Durability (resistance to weathering)

Shape and surface texture

Relative density and absorptionGradation

Deleterious substancesCrushing strength

Soft and lightweight particlesChemical stability

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Absorption

Dry SSD Wet

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Absorption

AW

D

M% Abs 100%M

MD

MAW

Question

A 1-ft3 bucket holds 100 lb. of aggregate. How much volume is occupied by the air and how much by the aggregate particles?

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Particle Density

Particle density is the ratio of the massof an aggregate particle to its own volume(also called mass density of solids).

3 3

M kg gor

V m cm

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Particle Density

Particle density can also be expressedas the ratio of the weight of an aggregateparticle to its own volume.

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3

W lbV ft

Relative Density

Relative density is the mass densityof an object relative to the mass densityof water (also called specific gravity).

w

RD w

M V

w

MV

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Relative Density

Relative density (specific gravity) canalso be expressed in weight-based units.

w

RD w

W V

w

WV

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Relative Density

Relative density depends on the volumeyou assume for the aggregate particles.

NetVolume

BulkVolume

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Relative Density

It also depends on the mass you assumefor the aggregate particles.

SSDMass

DryMass

Apparent Relative Density

D

NA

w

MR

VD

Net volume

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Bulk (OD) Relative Density

D

BB

w

MR

VD

Bulk volume

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SSD Relative Density

SSD

BSSD

wVM

RD

SSD aggregate

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Example

An aggregate sample has an oven-dry mass of3954.2 g, an SSD mass of 4006.8 g, and a netvolume of 1532.6 cm3.

Find RDA, RDB, RDSSD, and %Abs

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Question

A 1-ft3 bucket holds 100 lb of aggregate from the last example. How much volume is occupied by the air and how much by the aggregate particles?

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Question

A 1-m3 bucket holds 1500 kg of aggregate from the last example. How much volume is occupied by the air and how much by the aggregate particles?

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Measuring Relative Density

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Lab 4.8-2

Measuring Relative Density

w

MRD

Vmass of water displaced

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Measuring Relative Density

aggregate

water displaced

MRD

M

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Buoyancy

Mwater displaced × g

Min water × g

=Min air × g

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Measuring Relative Density

water displaced in air in waterM M M

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Apparent Relative Density

in air

Ain

OD

ODair in water

MRD

M M

Net volume

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Bulk (OD) Relative Density

in air

Bin aSSD

OD

ir in water

MRD

M M

Bulk volume

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SSD Relative Density

in air

SSDi

SSD

SSDn air in water

MRD

M M

Bulk volume

Measuring Relative Density

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Lab 4.8-3

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Measuring Relative Density

Mwater MblendMsand

~ 500 g

~ 500 g

~ 500 g

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Measuring Relative Density

water displaced water sand blendM M M M

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Apparent Relative Density

sandA

water sand

OD

ODblend

MRD

M M M

Net volume

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Bulk (OD) Relative Density

sandB

waterSsandS

blend

D

D

OMRD

M M M

Bulk volume

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SSD Relative Density

sandSSD

water sand

SSD

SSblen

Dd

MRD

M M M

Bulk volume

Achieving an SSD State

Coarse aggregate should be soaked in room temperature water for 24±4 h then rolled in a large absorbent cloth to remove all visible surface moisture.

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Achieving an SSD State

Fine aggregate should be brought to a moisture content of at least 6% and allowed to stand for 24±4 h. Aggregate is then spread out on a nonabsorbent surface and air is blown across it until it attains a free flowing condition.

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Achieving an SSD State

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