relative density and absorption - memphis - civil engineering handouts/3 - relative density... ·...

Relative Density and Absorption

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Aggregate Moisture

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).

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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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

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Bulk 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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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

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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 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

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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