# Relative Density and Absorption - Memphis - Civil Handouts/3 - Relative Density...Relative Density Relative density is the mass density of an object relative to the mass density of

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• Relative Density and Absorption

• CIVL 3137 76

Aggregate Moisture

Dry SSD Wet

• CIVL 3137 77

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?

CIVL 3137 78

• Particle Density

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

MV

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• 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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• CIVL 3137 81

Relative Density

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

NetVolume

BulkVolume

• Apparent Relative Density

D

NA

w

MR

VD

Net volume

CIVL 3137 82

• Bulk Relative Density

D

BB

w

MR

VD

Bulk volume

CIVL 3137 83

• SSD Relative Density

SSD

BSSD

wVM

RD

SSD aggregate

CIVL 3137 84

• 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

CIVL 3137 85

• Measuring Relative Density

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• Measuring Relative Density

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• Measuring Relative Density

w

MRD

Vmass of water displaced

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Measuring Relative Density

aggregate

water displaced

MRD

M

• CIVL 3137 90

Buoyancy

Mwater displaced g

Min water g

=Min air g

• CIVL 3137 91

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

• CIVL 3137 93

Bulk Relative Density

in air

Bin aSSD

OD

ir in water

MRD

M M

Bulk volume

• CIVL 3137 94

SSD Relative Density

in air

SSDi

SSD

SSDn air in water

MRD

M M

Bulk volume

• Achieving an SSD State

Coarse aggregate should be soaked in room temperature water for 244 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 244 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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