ITEM 407 TACK COAT
407.01
Description
407.02
Materials
407.03
Equipment
407.04 Weather
Limitations
407.05
Preparation of Surface
407.06
Application of Asphalt Material
407.07 Method
of Measurement
407.08 Basis of
Payment
407.01 Description. This work consists of
preparing and treating a paved surface with asphalt material, and cover
aggregate if required.
407.02 Materials. Conform to the applicable
requirements of 702 for the asphalt material and
use one of the following types: 702.04
RS-1, SS-1, SS-1h, CRS-1, CSS-1, or CSS-1h; or 702.13.
Conform
to 703.06 for cover aggregate.
407.03 Equipment. Provide adequate cleaning
equipment, spreader boxes, and distributors.
Use
distributors designed, equipped, maintained, and operated to apply asphalt
material at the specified rate per square yard (square meter) with uniform
pressure over the required width of application. Ensure that the
distributor includes a tachometer, pressure gauges, accurate volume measuring
devices, or a calibrated tank. Mount an accurate thermometer with a range
covering the specified application temperature for asphalt material at
approximately center height of the tank with the stem extending into the
asphalt material. Ensure that the distributor has a full-circulating
system with a spray bar that is adjustable laterally and vertically.
Ensure that the spray bar will maintain a constant height above the pavement
under variable load conditions. Supply each distributor with suitable
charts showing truck and pump speeds and other pertinent application data
necessary to obtain the required results.
Do
not use equipment that cannot obtain the correct tack application.
407.04 Weather Limitations. Do not
apply the asphalt material if the surface temperature is below the minimum
placement temperature for the pavement course to be placed, as specified in 401.06.
407.05 Preparation of Surface. Ensure
that the surface is thoroughly clean and dry when the asphalt material is
applied. Remove material cleaned from the surface and dispose of it as
the Engineer directs.
407.06 Application of Asphalt Material. Uniformly
apply the asphalt material with a distributor having clean nozzles functioning
properly. Obtain the Engineer’s approval for dilution with water, if
desired to achieve a more uniform application. The Department will not
pay for diluted tack used without approval. Ensure any diluted asphalt
material used for tack has a minimum viscosity of 20 seconds Saybolt Furol (702.04).
For
irregular areas such as driveways and intersections, apply the asphalt material
using a method the Engineer approves.
If
paving asphalt concrete directly onto Portland cement concrete or brick
pavement, tack the pavement with SBR asphalt emulsion
conforming to 702.13.
Before
placing a surface course onto an intermediate course, apply a tack coat on the
intermediate course.
Apply
the tack coat in a manner that offers the least inconvenience to traffic.
Only apply the tack coat to areas that will be covered by a pavement course
during the same day. Ensure the tack breaks before releasing to traffic unless
the paver is equipped with a spray bar system to apply tack just prior to mat
placement.
Obtain
the Engineer's approval for the quantity, rate of application, temperature, and
areas to be treated before application of the tack coat. The Engineer
will determine the actual application in gallons per square yard (liters per
square meter) by a check on the project.
The
application is considered satisfactory when the actual rate is within ±10
percent of the required rate and the material is applied uniformly with no
visible evidence of streaking, ridging or pickup by construction traffic.
The Engineer will require proper correction when ridging, streaking, pickup or
other non-uniform coverage is observed. Correct non-uniform tack only in
areas of non-uniform coverage. Do not reapply tack in areas where the
tack meetings uniformity and application requirements.
If the coverage is not uniform and not
corrected the total square yardage of non-uniform application will be
considered non specification material. The Engineer will
determine the number of gallons (liters) for non-payment by using the approved
rate of application times the total square yards (square meters) of non-uniform
application.
407.07 Method of Measurement. The
Department will measure Tack Coat and Tack Coat for Intermediate Course by the
number of gallons (liters) of undiluted asphalt material applied for each
according to Item 109.
407.08 Basis of Payment. The cost
of cover aggregate and water to dilute an emulsion is incidental to Tack Coat.
The
Department will not pay for non-uniformly applied materials as defined in 407.06.
The
Department will pay for accepted quantities at the contract prices as follows:
Item
Unit
Description
407
Gallon
(Liter)
Tack Coat
407
Gallon
(Liter)
Tack Coat for Intermediate Course