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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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