This work consists of
constructing a base course of aggregate and asphalt binder, mixed in a central
plant, and spread and compacted on a prepared surface.
The requirements of Item 401
apply, except as modified by this specification.
The Contractor shall furnish
aggregate for the mix that conforms to the following gradation:
|
Sieve Size |
Total Percent Passing |
|
2 inch (50 mm) |
100 |
|
1 inch (25.0 mm) |
75 to 100 |
|
1/2 inch (12.5 mm) |
50 to 85 |
|
No. 4 (4.75 mm) |
25 to 60 |
|
No. 8 (2.36 mm) |
15 to 45 |
|
No. 16 (1.18 mm) |
10 to 35 |
|
No. 50 (300 µm) |
3 to 18 |
|
No. 200 (75 µm) |
1 to 7 |
The Contractor may use
reclaimed asphalt concrete pavement (RAP) or reclaimed asphalt shingles (RAS)
as per 401.04. The Laboratory will establish the JMF according to 401.02.
Asphalt concrete is sampled
and tested by the Contractor at the asphalt plant. The Contractor quality control tests should
be based on the random number procedure found in the Contractor’s QCP. Random number along with sample tonnage location and
time should be recorded on the TE-199.
Contractor tests are used for pay if they are verified by District
testing. See 403.06
for sampling details.
The Contractor must notify
the Engineer at least 24 hours before the start of paving. Spreading equipment must conform to 401.12
specifications. The Contractor must
submit in writing, the model of asphalt spreader to be used, provide a
certification statement that all required modifications have been made, and provide a signature. The maximum compacted thickness of any one
lift is 6 inches. The uncompacted lift thickness will be greater than 6
inches by approximately 1/4 inch per inch of compacted thickness.
The minimum air temperature required for paving 301 base is 40 °F (5 °C). The minimum mixture temperature when
delivered to the paver is 250 °F (120 °C).
When using warm mix asphalt, the minimum temperature is 230 °F (110
°C). The mixture temperature should be
checked at a minimum of four times per day or more if necessary. The temperature should be documented in the
project records.
Hauling
must conform to specification 401.11.
The Contractor must use
trucks for hauling asphalt concrete that have tight, clean, smooth metal beds
from which the entire quantity of mixture is discharged smoothly into the
spreading equipment.
If transporting hot asphalt
concrete at prevailing air temperatures below 50 °F (10 °C), or if the length of haul exceeds 20 miles (32 km), ensure that all
truck beds are insulated to maintain workable mix temperature and ensure that
all covers are fastened to exclude the wind.
Do not exceed a distance of 50 miles (80 km) from the asphalt concrete
plant to the paving site, unless specified by the Department.
Compaction must conform to specification 401.16.
Compact the mixture uniformly
using a combination of both steel and Type I pneumatic tire rollers which
conform to 401.13. Do not use a spreading rate that exceeds the
total of the specified capacities of the rollers in use. A pneumatic tire roller is required for
compaction of base mixes. The type and
number of rollers must be documented in the project records.
Ensure that the maximum
compacted depth of any one layer is 6 inches (150 mm) and the temperature
of the mixture, when delivered to the paver (not to the job site), is a minimum
of 250 °F (120 °C).
Example: Roller capacity and placement rate.
A
contractor is using one 3-wheel roller, one vibratory roller with 66-inch drums
(both vibrating), and one Type I pneumatic tire roller to compact a 5-inch
thick mat using material with a Laboratory conversion factor of 2.0 tons per
cubic yard.
From
Table 401.13-1, the following is the capacity of the rollers the Contractor
will use:
·
Three-wheel = 700
sq yd/hr
·
Vibratory r oller = 2 drums x
66 in x (15 sq yd/in of width) = 1,980 sq yd/hr
·
Type I pneumatic
roller = 1,000 sq yd/hr
·
Maximum roller
capacity = 700 + 1,980 + 1,000 = 3,680 sq yd/hr
[(3,360 sq yd/hr) X (9 ft2/sq yd) X (5 in)
X (1 ft/12 in)] X (1 yd3/27 ft3)
= 511.11 yd3/hr.
511.11 yd3 X 2.0 tons/Yd3
= 1,022.22 tons per hour maximum
placement rate.
Spread the mixture at the
rate calculated using the specified thickness, the compacted width of the
pavement course being placed, and the weight-to-volume conversion factor
established in 401.21. Maintain the actual rate of spreading the
mixture within a tolerance of ±5 percent.
Do not exceed 3/8 inch (10
mm) in surface variation from the edge of a 10-foot (3 m) straightedge. Surface variations include bumps and
depressions. If using Item 301,
Asphalt Concrete Base, as a subbase for a rigid
pavement or base, do not exceed a variation of 1/4 inch in 10 feet (6 mm).
Example: Determining the
required placing rate per station (RPRS).
A contractor is placing a
5-inch uniform mat of asphalt concrete pavement whose Laboratory conversion
factor is 2.0 tons/cubic yard. The
required placing rate (RPRS) in tons of material per
station for a 12-foot wide mat is:
RPRS = [Volume of
asphalt in cubic yards] x [Lab Conversion Factor]
=
[{100 ft per station X 12 ft X (5 in ÷ 12 in/ft)} ÷ 27 ft3/
yd3] X 2.0 tons/yd3
= 37.04 tons/station
1.
Document
condition of base material at the time of paving (example: primed 304,
clean and dry concrete, etc.).
2. Obtain JMF for the project.
3. Obtain letter from Contractor stating paver to be used
and certifying that all modifications have been made as required.
4. Document tack or prime used along with source and
quantity used versus required.
5. Document surface and air temperatures.
6. Write location (station), date, and time on asphalt
plant tickets. Tickets should be totaled
daily and initialed with the calculator tape attached.
7. Document lift thickness, mat width, weather
conditions, surface tolerance checks, equipment problems, mat problems
(segregation, tearing, tenderness, etc.), spreading rate, roller coverage, and
any other issues or observations made during paving operations.
8. Obtain and document temperature of the mix at project
site and place this information on ticket of load checked. This should be done a minimum of four times
daily or any time temperature is in question.
9. Document the kind of rolling equipment and maximum
tons per hour allowed. See the example, “Roller Capacity and Placement
Rate.”
10. Calculate and document the quantity of material placed
for payment.
11. Document on form CA-FP-4
or other approved forms as needed.