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APPENDIX E
Pennsylvania Design Method for Seal Coats and Surface Treatments
A. MATERIAL NEEDED
A 25 kg (50 lb) representative sample of stone to be used.
B. INFORMATION NEEDED
1. Average Daily Traffic (ADT)
2. Condition of the existing surface to be treated out of
the following five categories.
(a) Flushed asphalt surface. Significant portion of
the pavement has free bitumen on the surface.
(b) Smooth nonporous surface. Tightly textured
surface; fine and/or coarse aggregate are tightly enmeshed in a
bitumen matrix.
(c) Slightly porous, oxidized surface. Beginning
stage of oxidation; small pieces of fine and/or coarse aggregate
are beginning to ravel out of the surface.
(d) Slightly pocked, porous and oxidized surface.
Characterized by significant loss of fine and/or coarse
aggregate from the pavement surface.
(e) Badly-pocked, porous and oxidized surface. Severe
loss of surface aggregate; remaining aggregate can be loosened
easily; the bitumen holding the aggregate is dry with complete
loss of sticky characteristic. This category should also be used
for treating open graded mixture surfaces, such as, FB-1 and
FB-2.
3. Type of bitumen to be used (asphalt,
cement/cutback/emulsion).
4. Type of aggregate (limestone/gravel/slag).
C. EQUIPMENT NEEDED
1. 9.44 liters[(one-third cubic Ft.)] Unit Weight Steel
Bucket (Inside Dimensions 203 mm (8.0") Dia. x 292 mm (11.5") H)
meeting AASHTO T19.
2. Large Scoop 115 mm (4-1/2") wide x 230 mm (9") long.
3. Heavy Duty Portable Platform Style Scale, capacity 100
kg (205 lbs.) with 0.005 kg (0.01 lb.) sub-graduations.
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4. Mechanical or portable hand-operated sieve shaker,
capacity 6 full height or 13 half-height 203 mm (8") dia. sieves
with pan and cover.
5.
A set of sieves 25 mm (1"), 19.0 mm (3/4"), 12.5 mm
(½"), 9.5 mm (3/8"), 4.75 mm (#4) and 2.36 mm (#8) with pan,
cover and cleaning brush (meeting AASHTO M92).
6. PENNDOT Forms TR-303 (Fig. 1), TR-304 (Fig. 2), TR-305
(Fig. 3), TR-306 (Fig. 5) and TR-307 (Temperature Conversion
Chart). Use the latest edition of these forms.
D. TESTING PROCEDURE
1. Loose Mass Determination:
This method is given in AASHTO T19. The procedure is as
follows:
(a) Weigh the 9.44 liters(one-third cubic ft.) steel
bucket empty.
(b) Fill the bucket to overflowing by means of a
scoop, discharging the aggregate from a height not to exceed 50
mm (2 inches) above the top of the bucket. Give the bucket 1/4
turn after each scoopful is placed. Exercise care to prevent, as
far as possible, segregation of the particle sizes of which the
sample is composed. Level the surface of the aggregate with the
fingers or a straightedge in such a way that any slight
projections of the larger pieces of the stone approximately
balance the larger voids in the surface below the top of the
bucket.
(c) Determine the mass of the bucket plus aggregate.
(d) Determine the net mass of the aggregate by
subtracting the mass of the empty bucket.
(e) The net mass multiplied by 105.932 (3) would give
the loose unit weight per cubic meter (foot), if the bucket is
exactly 9.44 liters (1/3 cu.ft.).
2. Sieve Analysis and Gradation:
This method is given in Field Test Manual (PTM No. 616).
The procedure is as follows:
Dry the aggregate in air. Hot plates may be used when test
results must be obtained quickly. Sample of aggregate should
have a minimum mass as follows:
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AASHTO #8 5 kgs (10 lbs).
AASHTO #67 13 kgs (26 lbs).
The sample shall be sieved over sieves of various sizes
required by the specifications. For example: 12.5 mm (½"), 9.5
mm (3/8"), 4.75 mm (#4) and 2.36 mm (#8) sieves are required for
AASHTO #8 aggregate, and 25.0 mm (1"), 19 .0 mm (3/4"), 9.5 mm
(3/8"), 4.75 mm (#4) and 2.36 mm (#8) are required for AASHTO
#67 aggregate. The sieving operation shall be conducted by means
of a circular motion of the sieve accompanied by jarring action
to keep the sample moving continuously over the surface of the
sieve.
The mass of the material passing each sieve and retained on
the next shall be recorded, starting with the pan mass (passing
2.36 mm (#8)) and continuing up to and including the maximum
sieve size (Col. A, Table 1).
The mass of each size aggregate shall be obtained by
weighing the pan material and accumulating the mass of each
increasing sieve size (Col. B. Table 1).
Calculate the total percent passing each sieve as shown in
Col. C, Table 1. Percentages shall be reported to the nearest
whole number.
TABLE 1. GRADATION WORK SHEET
**(METRIC SYSTEM)**
Example: AASHTO # 8 Stone, Initial mass 5 kgs.
Passing
Sieve
Size
12.5 mm
9.5 mm
4.75 mm
2.36 mm
Pan
Mass of Material
on sieve, kgs.
A
0
0.50
3.50
0.75
0.25
Accumulative
Mass
Passing, kgs.
B
5.0
4.50
1.00
0.25
---
Total Percent
Passing
C
100
90
20
5
--
**(ENGLISH SYSTEM)**
Example: AASHTO # 8, Initial mass 10 lbs.
Passing
Sieve
Size
Mass of Material
on sieve, lbs.
Accumulative
Mass
Passing, lbs.
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Total Percent
Passing
½"
3/8"
#4
#8
Pan
A
0
1.0
7.0
1.5
0.5
B
10.0
9.0
2.0
0.5
---
C
100
90
20
5
--
NOTE: Average stockpile gradation obtained from the aggregate
producer can be used in lieu of the above test.
E. DESIGN PROCEDURE FOR SINGLE APPLICATION (SEAL COAT)
On Gradation Chart (Fig. 1), plot the various percentages
passing each sieve size, obtained in the sieve analysis. Connect
the points by straight lines to obtain the gradation line.
Determine the median size in millimeters (inches) of the stone
as per instructions given on Figure 1 (PENNDOT Form TR-303).
Quantity of Stone (kilograms per sq. meter pounds/sq.yd.)):
Use the nomograph in Fig. 2 (PENNDOT Form TR-304) to
determine the quantity of stone required. The instructions to
use the nomograph are given in the figure. Usually, Line B which
accounts for 10% whip off loss should be used. Line A should be
used for shoulder work, for roads carrying ADT of less than 100,
and for seal coats with pre-coated aggregate. Line A can also be
used if the past experience indicates minimal whip-off loss.
Quantity of Bitumen (liters per sq. meter (gal./sq.yd.)):
Use the nomograph in Fig. 3 (PENNDOT Form TR-305) to
determine the quantity of bitumen. Follow the instructions given
in the figure. The application rate obtained in liters per sq.
meter (gal./sq.yd.)is based upon the bitumen volume at 15.6 oC
(60 oF). Like most materials, bitumen's expand when heated, and
to control the quantities being applied during construction,
measurement of bitumen must be made in the distributor at the
spraying temperature. Therefore, if application temperature is
more than 15.6 oC (60 oF), which is usually the case, the rate of
application during construction should be increased. This can be
determined by using Figure 4 (PENNDOT Form TR-307).
For shoulder work, use the line 'ADT Less Than 100 in
Quadrant 1.
It is not necessary to add 0.14 liters/m2 (0.03 gal./sq.yd.)
if the slag or absorptive gravel aggregate is precoated with
bitumen.
Normally, Category e (badly pocked, porous and oxidized
surface) should be used for the surface of open graded mixes,
such as, FB-1 and FB-2. However, if the surface is excessively
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open, add 0.23 L/m2 (0.05 gal./sq.yd.) to allow for the loss of
bitumen in the open voids.
F. DESIGN PROCEDURE FOR DOUBLE APPLICATION (SURFACE TREATMENT)
On Gradation Chart (Fig. 1), plot the various percentages
passing each sieve size, obtained in the sieve analysis of
AASHTO #67 and #8 aggregate to be used for double application.
Determine the median size (in millimeters (inches)) of both
aggregates as per instructions given on Figure 1.
Quantity of Stone (kilograms per sq. meter (lbs./sq.yd.)):
Use the nomograph in Fig. 2 to determine the quantity of
AASHTO #67 (first application) corresponding to its median size
and loose mass. Always use Line A in Quadrant 1 for the first
application. Similarly, obtain the quantity of AASHTO #8 (second
application) using Line A or Line e depending on the estimated
whip-off loss as discussed in seal coat design.
Quantity of Bitumen (liters per sq. meter (gal./sq.yd.)):
Use the nomograph in Fig. 5 to determine the quantity of
bitumen for each application. Follow the instructions given in
Fig. 5. Add 0.27 liters/m2 (0.06 gal./sq.yd.) to Total Bitumen Q
if a slag or absorptive gravel aggregate is used in the double
application.
The first application rate (0.4Q) obtained from Fig. 5 is
based on the assumption that the existing surface is smooth and
nonporous (Category b). If the existing surface falls into other
categories, increase the first application rate (0.4Q) by the
amount shown below:
Category
(c)
(d)
(e)
Existing Surface Condition
Add liters/sq.m
(gal./sq.yd.)
0.14 (0.03)
Slightly porous, oxidized surface
Slightly pocked, porous and oxidized
surface
0.27 (0.06)
Badly-pocked, porous and oxidized surface (or open graded mixes, such as,
FB-1 and FB-2)
0.41 (0.09)
Make temperature corrections to first and second
application rates using Figure 4.
G. NOTES ON DESIGN PROCEDURES
Application of seal coats and surface treatments is an art.
The design is a guide to estimate the application rates of
bitumen and stone. It may be necessary to adjust these rates to
suit the actual field conditions. For example, the stone
application rate obtained by these design procedures is based on
the assumption that the stone is cubical in shape. If the stone
actually used tends to be flatter, the application rate has to
be reduced to obtain a single layer on the following pages the
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metric design form is followed immediately by the current
English unit form.
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EXAMPLES ON DESIGN OF
SEAL COATS AND SURFACE TREATMENTS
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EXAMPLE NO. 1
DESIGN OF SINGLE APPLICATION (SEAL COAT)
A. AGGREGATE
AASHTO #8 Limestone Aggregate. A 25 kgs (50 lb)
representative sample was obtained from the stockpile.
B. INFORMATION GATHERED
1. Average Daily Traffic (ADT) = 450
2. Condition of the existing surface to be treated:
Slightly pocked, porous and oxidized surface
3. Type of bitumen to be used: E-2 or E-3 Emulsified
Asphalt
4. Type of Aggregate: AASHTO #8 Limestone
5. Assume 10% whip-off loss
C. TESTING OF AGGREGATE
1. Loose Mass Determination (AASHTO T19): The stone weighed
1600 kg per m3 (100 lbs per cu. ft.).
2. Sieve Analysis and Gradation: Initial mass of the stone
graded was 6 kg (12 lbs.). The worksheet follows:
**(METRIC SYSTEM)**
Passing
12.5 mm
9.5 mm
4.75 mm
2.36 mm
Pan
Accumulative
Mass
Passing, kg
6.00
5.10
0.90
0.20
-
Mass of Material
on sieve, kg
0
0.90
4.20
0.70
0.20
Total Percent
100
85
15
3
-
D. DESIGN OF SINGLE APPLICATION
Plot the various percentages passing sieves 12.5 mm, 9.5
mm, 4.75 mm and 2.36 mm on the Gradation Chart (see Figure 1 -
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Example No. 1).
obtain the gradation
line and 50% passing
the millimeter scale
Connect the points by straight lines to
line. From the intersection of gradation
line, draw a line vertically downward to
and read the median size as 6.8 mm.
**(ENGLISH SYSTEM)**
Passing
½"
3/8"
#4
#8
Pan
Accumulative
Mass
Passing, lbs
12.0
10.2
1.8
0.4
-
Mass of Material
on sieve, lbs
0
1.8
8.4
1.4
0.40
Total Percent
100
85
15
3
-
D. DESIGN OF SINGLE APPLICATION
Plot the various percentages passing sieves ½", 3/8", #4 and
#8 on the Gradation Chart (see Figure 1 - Example No. 1). Connect
the points by straight lines to obtain the gradation line. From
the intersection of gradation line and 50% passing line, draw a
line vertically downward to the millimeter scale and read the
median size as 6.8 mm. Divide 6.8 by 25.4 to convert mm to
inches. So the median size is 0.27 inch.
Quantity of Stone (kilograms per sq. meter):
See Fig. 2 of Example 1. Enter Quadrant 1 on the left at
6.8 mm (0.27 inch) median size. Go horizontally to the right to
Line B (10% whip-off). Proceed vertically downward to Quadrant 2
and intersect with 1600 kgs per cu. meter (100 lbs/cu. ft.)
line. Proceed horizontally to left to find the spread in kg/m2
=12.75 (lbs/sq.yd. = 23.5). So the quantity of stone for the
single application is 12.75 kg per sq. meter (23.5 lbs. per
sq.yd.). Quadrant 3 can be used, if necessary, for computing the
tonnes (tons) of stone required per station. If the roadway or
spread width is 3.66 m (12 ft.), 46.13 tonnes (1.55 tons)of
stone would be required per station.
NOTE: Use Line A (0% whip-off) if the seal coat is applied
on shoulder or precoated stone is used or the past
experience indicates minimal whip-off loss.
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Quantity of Bitumen (liters per sq. meter (gal. per sq.
yd.)):
See Fig. 3 of Example 1. Enter Quadrant 1 on left at 6.8 mm
(0.27 inch) median size. Go horizontally to the right to
intersect with 100-500 ADT line (since ADT = 450). Proceed
vertically downward and enter Quadrant 2 to intersect with
appropriate surface condition line. In this example, the surface
is slightly pocked, porous and oxidized. Proceed horizontally
from this point to the left and enter Quadrant 3 to intersect
with applicable type of bitumen (emulsion in this case). Proceed
vertically to read quantity of bitumen in liters per sq. meter
(at 15.5 oC) [gal. per sq.yd. (at 60 oF)] = 1.698 (0.375 ).
Assume that the temperature of E-2 or E-3 emulsion in the
distributor is 74 oC (165 oF). Use Fig. 4 to determine the
application rate at 74 oC (165 oF). Enter the graph at 15.5 oC
(60 oF) temperature, proceed vertically to intersect with
emulsion line and then proceed horizontally to the left to read
the application factor = 1.031. Obtain the application rate at
74 oC (165 oF) as follows:
1.031 x 1.698 (0.375) = 1.751 L/m2 (0.387 gal./sq.yd.).
So the bitumen application rate (at 74 oC (165
job shall be 1.75 liters/m2 (0.39 gal./sq. yd.).
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o
F)) on the
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EXAMPLE NO. 2
DESIGN OF DOUBLE APPLICATION (SURFACE TREATMENT)
A. AGGREGATES
AASHTO #8 and #67 Limestone Aggregates
B INFORMATION GATHERED
1. Condition of the existing surface to be treated: Badly
pocked, porous and oxidized surface.
2. Type of bitumen to be used: E-2 or E-3 Emulsified Asphalt
3. Type of Aggregate: Limestone
4. Assume 0% whip-off loss for the second application rate
C. TESTING OF AGGREGATE
1. Loose mass Determination (AASHTO T19): Assume that both
aggregates weighed 1600 kg/m3 (100 lbs/ft3).
2. Sieve Analysis and Gradation: See Example No. 1 for
worksheet. Assume that #8 stone has the same gradation as given
in Example No. 1 and has a median size of 6.8 mm (0.27 inch).
The following gradation was obtained for #67 stone:
Sieve SizePercent Passing
25
mm (1 ")
100
19.0 mm (3/4")
96
9.5 mm (3/8")
45
4.75 mm (#4)
6
2.36 mm (#8)
2
The above gradation has been plotted on Fig. 1 (Example No.
2) and the median size has been determined to be 10.2 mm (0.40
inch).
D. DESIGN OF DOUBLE APPLICATION
Quantity of Stone (kilograms per sq. meter (lbs./ sq. yd.):
See Fig. 2 of Example 2. Enter Quadrant 1 on the left side
at 10.2 and 6.8 mm (0.40 and 0.27 inch) median sizes for #67 and
#8 aggregates, respectively. Go horizontally to the right to Line
A (0% whip-off). Proceed vertically downward to Quardrant 2 and
intersect with 1600 kg per cubic meter (100 pounds per cu. ft.)
line.
Proceed horizontally to the left to find the spread in
kg/m2 (lbs/sq. yd). The following application rates are
obtained:
#67 17.09 kgs/m22 (31.5 lbs./sq. yd.)
#8 11.39 kgs/m (21.0 lbs./sq. yd.)
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Quantity of Bitumen (liters per sq. meter (gal./sq. yd.):
See Fig. 5 of Example 2. Enter Quardrant 1 on the left side
at 10.2 and 6.8 mm (0.40 and 0.27 inch) median sizes for Pa. #67
and #8 aggregates, respectively. Go horizontally to the right to
Line C. Proceed vertically downward to Quadrant 2 and intersect
with applicable type of bitumen (emulsion in this case). Proceed
horizontally to the left to read quantities of bitumen as
follows:
Q1 = 1.834 liters/m2 (at 15.5 oC) (0.405 gal./yd2. (at 60°F))
Q2 = 1.245 liters/m2 (at 15.5 oC) (0.275 gal./yd2. (at 60°F))
Total bitumen (Q) required for double application = Q1 + Q2
2
=1.834 + 1.245 = 3.08 liters/m
(0.405 + 0.275 = 0.68 gal./yd2.)
NOTE: If a slag or absorptive gravel aggregate is used, the
total bitumen (Q) should be increased by 0.27 liter/m2 (0.06
gal. per sq. yd). This example involves limestone
aggregates.
Bitumen required for first application on a smooth,
nonporous surface
= 0.4 Q = 0.4 x 3.08 (0.68) = 1.23 liter/m2 (0.27 gal./yd2.)
Since the existing surface is badly pocked, porous and
oxidized, add 0.41 liter/m2 (0.09 gal/yd2.). The corrected bitumen
required for first application
2
= 1.23 + 0.41 = 1.64 liters/m
2
(0.27 + 0.09 = 0.36 gal/yd .)
Bitumen required for second application
2
2
= 0.6 Q = 0.6 x 3.08 (0.68) = 1.85 liters/m (0.41 gal./yd .)
2
These application rates in liter/m (gal./sq. yd.) are at
o
15.6 C (60°F), so make temperature corrections using Fig. 4 (see
Example 1 for procedure) corresponding to the actual temperature
of the emulsion in the distributor.
If the emulsion temperature is 74 oC (165°F), the
o
application rates at 74 C (165°F) will be:
First Application Rate = 1.031 x 1.64 (0.36) = 1.69 liters/m2
(0.37 gal/sq. yd.)
Second Application Rate = 1.031 x 1.85 (0.41) = 1.91 liters/m2
(0.42 gal/sq. yd.)
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