Construction requirements for
prime coats are included in 408. An asphalt material having low viscosity is
required for a prime coat. This material
is intended to penetrate a prepared granular surface prior to the placement of
an asphalt concrete mixture. The purpose
is to bind the granular particles together for some depth below the surface to
provide additional stability.
One of the following types of
asphalt material can be used: 702.02
MC-30, MC-70, or MC-250 or 702.03
Primer 20.
Cover aggregate must conform
to No. 9 size or gradation requirements of 703.05
or 703.06.
Prime coat cannot be used on
a wet surface.
Do not apply prime coat for
asphalt concrete paving or surface treatment work when the air temperature is
below 50 °F or when the air temperature in the last 24 hours has been 40 °F or
lower.
Do not apply prime coat on
stabilized or granular base courses when the air temperature is below 40 °F.
Equipment requirements for
the application of tack coat are the same as detailed in 407. These requirements include the use of
tachometer, pressure gauges, and an accurate volume measuring device or a
calibrated tank. A thermometer is
required to monitor temperature of the tack.
The spray system must by fully circulating and the spray bar must be
adjustable both laterally and vertically.
The Contractor must provide charts or other information that shows truck
and pump speeds required to obtain the application rate.
The spreading of the cover
aggregate, when required, can be accomplished by any approved method depending
upon the specific job conditions. When
sweeping is required, the brooms approved for use should produce a uniform
surface without causing damage.
The surface to be primed
should meet all requirements for the particular specification item (e.g.,
subgrade, aggregate base, stabilized subgrade, etc.). Irregularities in the subgrade, subbase, or
base material in excess of specified tolerances must be repaired prior to
priming. These include, but are not
limited to, ruts, corrugations, and high and low areas. Mud, clumps of dirt, and other foreign material
must be cleaned from the surface to be primed.
The specified application rate
for the asphalt material is an estimated rate suitable for average
conditions. Open textured surfaces may
permit an increase, while dense surfaces may require a reduction in the
estimated rate. The application rate
should be such that the prime will be absorbed by the material within 24 hours.
The asphalt material must be
applied uniformly over the entire width of the area to be primed. The distributor must meet the same
requirements of 407.03. If excess material is applied, the Contractor
should squeegee the excess from the surface.
Any deficient or skipped areas must be coated.
Prime is shipped under ODOT’s
Asphalt Materials Certification Requirements as detailed in Supplement
1032. Weight tickets will be
provided for the loads of asphalt material delivered to the project. A weigh-back ticket must be provided to
accurately determine the quantity of tack used based upon weight. This weight will have to be converted to
gallons based on the appropriate conversion factor for the tack. Although the distributor is required to have
an accurate volume measuring device, payment must be made using the weight
tickets.
When traffic must use the
primed area where the material has not penetrated completely, cover aggregate
must be applied to absorb any excess material.
Determine gallons (liters)
from weight tickets or weighed partial loads (weigh-back). For weights or volumes that are questionable
or unknown, a volume-measuring device is required before accepting the
material. Cover aggregate is included in
the bid price for the prime coat.
1.
Measure and
document air temperature.
2. Document surface preparation (sweeping, cleaning) and
condition of surface prior to the application of the prime coat.
3. Document the temperature of material as delivered to
the project.
4. Document equipment used and conformance to
specifications.
5. Document the use of any cover aggregate.
6. Document any issues with application (excess,
deficiency) and actions taken to correct the issue.
7. Calculate and document, for pay, number of gallons
applied per 408.09,
408.10,
and 109.01.
8. Use form CA-FP-6
and other approved forms to document the tack application and calculations.