This document provides information on aggregates used in construction, including their definition, sources, classification, properties, and specific gravity tests. It defines aggregates as crushed stone, gravel, sand or other particulate materials used in construction. The key points made are: - Aggregates make up 60-80% of concrete and over 80% of asphalt by volume. - They can come from natural sources like quarries or be manufactured from materials like slag. - Important aggregate properties include gradation, shape, hardness and absorption. - Specific gravity tests determine the bulk specific gravity when dry and saturated surface dry.

1. 1
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Aggregates
HMA Surface
Dr. Sherif El-Badawy Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
http://www.pavementinteractive.org
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Aggregate
Definition:
• A mass of crushed stone, gravel, sand, …. Etc.
• Composed of individual particles.
• May include clays and silts.
Uses:
• Underlying materials for pavements:
• (Base & Subbase).
• Ingredient in PCC and AC
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Aggregates
In PCC:
• 60% to 75% by volume
• 79% to 85% by weight
In AC:
• Over 80% by volume
• 92% to 96% by weight

2. 2
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Aggregate Sources
Natural:
• Gravel pits.
• River run deposits.
• Rock quarries.
Manufactured:
• Slag waste from steel mills and expanded shall
and clays  Light weight agg.
• Styrofoam  Light weight agg.
• Steel slugs and bearings  Heavy weight agg.
•
• Recycled Materials
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Geological Classification
Igneous -- cooled from molten magma
• Intrusive
• High density granite, cooled slowly below ground
• Extrusive
• Basalt (lava) cools rapidly above ground
• Large air pockets may form creating low density cinder &
pumice
Sedimentary
• Disintegrated minerals moved by gravity, wind, water, or ice and
deposited as sediment in nearly horizontal layers
• These deposits may eventually be compressed into sandstone,
limestone, shale, conglomerate, gypsum
Metamorphic
• Minerals are changed by heat and pressure
• Crystals partially melt & grow into quartzite, marble, slate, etc.
Mansoura University - Faculty of Engineering – Public Works Engineering Dept. Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Aggregate Terminology
• Aggregate
• Coarse Aggregate (CA)
• Fine Aggregate (FA)
• “Fines” (Mineral Filler: MF)
• Maximum Size
• Nominal Max. Size

3. 3
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Sieve Designation
• Sieve Opening: for sieves greater than ¼ in.
• Number of Openings per Linear Inch.
Sieve Designation Sieve Opening (in.)
75 mm 3 in. 3.0
37.5 mm 1 ½ in. 1.5
19.0 mm ¾ in. .75
12.5 mm ½ in. .5
6.3 mm ¼ in. .25
4.76 mm No. 4 .187
2.36 mm No. 8 .0937
1.18 mm No. 16 .0469
0.6 mm No. 30 .0234
0.3 mm No. 50 .0117
0.15 mm No. 100 .0059
0.074 mm No. 200 .0029
CA
FA
MF
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Definition of Gravel and Crushed Stone
Gravel - Natural Particles No. 4
to 3 in. Size and the Particles tend
to be Smooth and Rounded.
Crushed Stone - Artificially
Crushed Rock, Boulders, or Large
Cobbles. Most or All of the
Surfaces are from Crushing, and
the Particle Edges tend to be Sharp
and Angular.
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
• Gradation
• Particle Shape and Surface Texture
• Hardness
• Toughness
• Soundness
• Deleterious Materials
Aggregate Characteristics
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Maximum and Nom. Max. Aggregate Size
• Nominal Maximum Aggregate Size. The largest sieve that
retains some of the aggregate particles but generally not
more than 10% by weight.
• Superpave defines nominal maximum aggregate
size as "one sieve size larger than the first
sieve to retain more than 10 percent of the
material“.
• Maximum Aggregate Size: The smallest sieve size through
which 100% of the aggregate sample particles pass.
• Superpave defines the maximum aggregate
size as "one sieve larger than the nominal
maximum size“.

4. 4
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Grain Size Distribution Table
sieve
#
Sieve
size
(mm)
%
Passing
3/4 ″ 19.00 100
3/8 ″ 9.50 100
4 4.750 95
8 2.360 84
16 1.180 74
30 0.600 53
40 0.425 41
50 0.300 31
100 0.150 14
200 0.075 3.80
Pan --- 0.00
Maximum Aggregate Size = 9.5 mm
Nominal Maximum Aggregate Size =4.75 mm
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Grain Size Distribution Curve
• Semi-logarithmic for PCC and Soils
• Fuller Curve  for HMA (hot mix asphalt
aggregate gradation)
Pi = 100(di/D)n
Pi = % passing a sieve of size di
di = sieve size i
D = Maximum size of aggregate
n = 0.5 (Fuller), n = 0.45  FHWA (0.45
gradation chart)
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Semi-logarithmic Grain Size Dis. Curve
0
10
20
30
40
50
60
70
80
90
100
0.0001 0.001 0.01 0.1 1 10
Grain Size (mm)
PercentPassing(byweight)
Silica Sand
Piedmont Silt
Plastic Kaolin
CLAY SIZE SILT SIZE SAND SIZE GRAVEL
0.075 mm
Fine-Grained Soils Coarse-Grained Soils
Grain Size (mm)
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Grain Size Distribution Curve
(0.45 Power Gradation Table)
sieve # Sieve size (d)
(mm)
% P of the
aggregate
(d)0.45
pi = 100(di/D)0.45
(FHWA Max Density
Line), %
3/8 9.5 100 2.754 100(9.5/9.5)0.45 =100
4 4.75 95 2.016 100(4.75/9.5)0.45 =73
8 2.36 84 1.472 53
16 1.18 74 1.077 39
30 0.6 53 0.795 29
40 0.425 41 0.680 25
50 0.3 31 0.582 21
100 0.15 14 0.426 15
200 0.075 3.80 0.312 11.3

5. 5
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Grain Size Distribution Curve (FHWA 0.45 Power Gradation
Chart)
0
10
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00 2.50 3.00
Sieve Size (mm)
%Passing
9.50
4.75
2.36
1.18
0.600
0.075
0.150
0.300
0.425
Max Density Line (FHWA
0.45 Power Curve)
d0.45
Aggregate Gradation) Max Size
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Gradation Types
Uniform
Well (Dense)
graded
Gap Graded
Open Graded
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Gradation Types
• Dense (well-graded): a gradation that is near the FHWA’s
0.45 Power Curve for maximum density.
• Gap Graded: a gradation that contains only a small
percentage of aggregate particles in the mid-size range. The
curve is flat in the mid-size range.
• Open graded: a gradation that contains only a small
percentage of aggregate particles in the small range. This
results in more air voids. The curve is near vertical in the
mid-size range, and flat and near-zero in the small-size
range.
• One Sized: a gradation with the majority of aggregates
passing one sieve (vertical line).
• Uniformly Graded. a gradation that contains most of the
particles in a very narrow size range. (almost vertical line).
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.

6. 6
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Particle Shape
Angular Rounded Flaky
Elongated Flaky & Elongated
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Particle Shape
Rounded
Angular
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Percent Fractured Faces
0% Crushed 2 or More
Fractured Faces
Surface Texture
Specs defines minimum percentage of
aggregates with fractured faces
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Voids and Moisture Absorption
Oven Dry (Bone Dry) Air Dry
SSD Moist
Permeable
Voids
Solid
Moisture

7. 7
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Absorption
Oven Dry (Bone dry)
• Zero moisture in voids
Air Dry
• Some moisture in voids (equal to atmospheric
humidity)
Saturated-Surface Dry (SSD)
• Voids totally filled with moisture but surface of
particles are dry
Moist
• Voids are filled and some surface moisture exists
• We want SSD for concrete so that mix water is not absorbed
and is available for workability and hydration
• We want dry aggregate for asphalt
• Some asphalt absorption is good for bonding and locking
• But, this uses a little more asphalt in the mix which is
slightly more costly
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Aggregate Specific Gravities
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
• All matter has mass and occupies space.
• Volumetrics are the relationships between mass
and volume.
• Superpave mix design based on aggregate and
mixture volumetrics
Volumetrics
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Specific Gravity, G
• Ratio of the mass to volume of an object to
that of water at the same temperature
Mass Solid
Volume
Mass Water
Volume

8. 8
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Densities
• Density is the unit weight of a material
 lb/ft3 or kg/m3
 Unit weight = g w G
gw = 1.000 g/cm3
gw = 1000 kg/m3
gw = 62.4 lb/ft3
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Gsb =
Mass, oven dry
Bulk Specific Gravity, Dry
Vol of agg, + surface voids
Vol. of water-perm. voids
Surface Voids
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Bulk Specific Gravity, SSD
Gs, ssd =
Mass, oven dry agg + mass water
Vol of agg, + surface voids
Vol. of water-perm. voids
Surface Voids
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Gsa =
Mass, oven dry agg
Apparent (true) Specific Gravity
Vol of agg

9. 9
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Specific Gravity Tests for Aggregates
• Two tests are needed:
• Coarse aggregate (retained on the 4.75 mm
sieve).
• Fine aggregate (passing the 4.75 mm sieve)
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Coarse Aggregate Specific Gravity
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Coarse Aggregate Specific Gravity
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Coarse Aggregate Specific Gravity
• ASTM C127
• Dry aggregate
• Soak in water for 24 hours
• Decant water
• Use pre-dampened towel to get SSD condition
• Determine mass of SSD aggregate in bucket
• Determine mass under water
• Dry to constant mass
• Determine oven dry mass

10. 10
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Coarse Aggregate Specific Gravity
• A = oven dry mass in air
• B = SSD mass
• C = mass under water (submerged
mass)
Gsb = A / (B - C)
Gs,SSD = B / (B - C)
Gsa = A / (A - C)
Water absorption, %
• Absorption % = [(B - A) / A] * 100
Calculations
Mass (=Volume) of water
displaced by the aggregate
1 gm water = 1 cc water
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Fine Aggregate Specific Gravity
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Fine Aggregate Specific Gravity
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Fine Aggregate Specific Gravity

11. 11
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Fine Aggregate Specific Gravity
• ASTM C128
• Dry aggregate
• Soak in water for 24 hours
• Spread out and dry to SSD
• Add 500 g of SSD aggregate to pycnometer of known volume
• Pre-filled with some water
• Add more water and agitate until air bubble have been
removed
• Fill to line and determine the mass of the pycnometer,
aggregate and water
• Empty aggregate into pan and dry to constant mass
• Determine oven dry mass
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Fine Aggregate Specific Gravity
• A = oven dry mass in air
• B = mass of pycnometer filled with water
• C = mass pycnometer, SSD aggregate and water
• S = mass SSD aggregate
Gsb = A / (B + S - C)
Gs,SSD = S / (B + S - C)
Gsa = A / (B + A - C)
Water absorption, %:
• Absorption % = [(S - A) / A] * 100
Calculations
Mass (=Volume) of water
displaced by the aggregate
1 gm water = 1 cc water
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Adhesion of Aggregate to Bitumen
• Some aggregates have an affinity for water over asphalt
(hydrophilic).
• These aggregates tend to be acidic and suffer from
stripping after exposure to water.
• Some aggregates have an affinity for asphalt over water
(hydrophobic).
• These aggregates tend to be basic and do not suffer from
stripping problems.
• Mineralogy and chemical composition of the aggregate are
important contributing factors to the stripping problem.
• Additionally, an aggregate’s surface charge when in
contact with water will affect its adhesion to asphalt
cement and its susceptibility to moisture damage.
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Stripping
•Loss of bond between aggregates and asphalt binder
•Typically begins at the bottom of the HMA layer and progresses
upward.

12. 12
Mansoura University - Faculty of Engineering – Public Works Engineering Dept.
Raveling
•Loss of bond between aggregates and asphalt binder.
•Typically begins at the surface of the HMA layer and progresses
downward.