03 - Relative Density and Absorption - Memphis Handouts/03 - Relative...CIVL 3137 2 Important...
Transcript of 03 - Relative Density and Absorption - Memphis Handouts/03 - Relative...CIVL 3137 2 Important...
Relative Density and Absorption
CIVL 3137 2
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
CIVL 3137 3
Absorption
Dry SSD Wet
CIVL 3137 4
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 5
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
CIVL 3137 6
Particle Density
Particle density can also be expressedas the ratio of the weight of an aggregateparticle to its own volume.
CIVL 3137 7
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
CIVL 3137 8
Relative Density
Relative density (specific gravity) canalso be expressed in weight-based units.
w
RD w
W V
w
WV
CIVL 3137 9
CIVL 3137 10
Relative Density
Relative density depends on the volumeyou assume for the aggregate particles.
NetVolume
BulkVolume
CIVL 3137 11
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
CIVL 3137 12
Bulk (OD) Relative Density
D
BB
w
MR
VD
Bulk volume
CIVL 3137 13
SSD Relative Density
SSD
BSSD
wVM
RD
SSD aggregate
CIVL 3137 14
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 15
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?
CIVL 3137 18
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?
CIVL 3137 21
Measuring Relative Density
CIVL 3137 24
Lab 4.8-2
Measuring Relative Density
w
MRD
Vmass of water displaced
CIVL 3137 25
CIVL 3137 26
Measuring Relative Density
aggregate
water displaced
MRD
M
CIVL 3137 27
Buoyancy
Mwater displaced × g
Min water × g
=Min air × g
CIVL 3137 28
Measuring Relative Density
water displaced in air in waterM M M
CIVL 3137 29
Apparent Relative Density
in air
Ain
OD
ODair in water
MRD
M M
Net volume
CIVL 3137 30
Bulk (OD) Relative Density
in air
Bin aSSD
OD
ir in water
MRD
M M
Bulk volume
CIVL 3137 31
SSD Relative Density
in air
SSDi
SSD
SSDn air in water
MRD
M M
Bulk volume
Measuring Relative Density
CIVL 3137 32
Lab 4.8-3
CIVL 3137 33
Measuring Relative Density
Mwater MblendMsand
~ 500 g
~ 500 g
~ 500 g
CIVL 3137 34
Measuring Relative Density
water displaced water sand blendM M M M
CIVL 3137 35
Apparent Relative Density
sandA
water sand
OD
ODblend
MRD
M M M
Net volume
CIVL 3137 36
Bulk (OD) Relative Density
sandB
waterSsandS
blend
D
D
OMRD
M M M
Bulk volume
CIVL 3137 37
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.
CIVL 3137 38
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.
CIVL 3137 39
Achieving an SSD State
CIVL 3137 40
CIVL 3137 41