- 327 - SECTION 504 -- TACK COAT
504.01 Description
1.Tack coat is the application of asphaltic materials to bases or surfacing. The tack coat shall be appl ied to surfaces on which bituminous materials will be placed. When spec ified, tack coat will be applied on other surfaces.
504.02 Material Requirements
1.The type and grade of emulsified asphalt shall be specified in the contract and shall conform to the requ irements in Sections 1031 or 1032. Fast-Set type emulsified asphalt shal l meet the requirements of Table 504.01. Table 504.01 CFS-1, FS-1 Emulsified Asphalt Requirements Tests on emulsion: Specification Viscosity, Saybolt Furol, T 59, 25oC (77oF), sec. 20 – 100 Sieve Test, Percent Retained, maximum (note 1) 0.10 Residue by Distillation, Percent, minimum 57.0 Storage Stability, Percen t, maximum (note 1) 1.0 Tests on distillation residue: Penetration, dmm. 40 - 175 Ductility, 25oC (77oF), cm., minimum 40 Solubility in Trichloroethylene, Percent, minimum 97.5 Note 1: See note “b” of AASHTO M 208 - 2015 Shall be formulated as either a cationic or anionic, fast-setting emulsion that is suitable for tack coat diluti on, and to have an accelerated breaking time in cooler temperature applications.
504.03 Construction Methods
1.Before the application of tack coat, the surface shall be cleaned as described in Section 501.
2.The Contractor shall furnish and apply the tack coat.
3.a. A pressure distributor shal l be used for the application of the tack coat. Uniform application is required. Hand sprayers may be used in applying tack coat to small or irregular sections.
b.Emulsified asphalt shall be diluted with potable water at a rate of one part water to one part emulsified asphalt by either the Supplier or the Contractor.
c.The rate of application shall be adequate to bond the new bituminous layer to the existing surface. This shall be from 0.10 to 0.20 Gal/SY (0.45 to 0.90 L/m2) when applied to existing or milled surfaces and from 0.05 to 0.10 Gal/SY (0.23 to 0.45 L/m2) when applied to the freshly laid asphaltic concrete.
4.The Contractor shall furnish and apply a tack coat as directed by the Engineer to seal surfaces and pr event infiltration of moisture when construction will be interrupted by weathe r or the project is shut down for the winter.
504.04 Tack Coat
- 328 - 504.04 -- Method of Measurement
1.Tack coat shall be measured in ga llons (liters) of diluted (field and refinery) solution applied to the surface.
504.05 Basis of Payment
1.P a y I t e m P a y U n i t Tack Coat Gallons (Gal) [Liter (L)] 2. Any amount of tack coat emul sified asphalt which is outside the specified property ranges of Table 504. 02, shall be paid for at the contract unit price multiplied by the pay factor determined in Table 504.02. If the resultant Pay Factor for the material indicates rejection as an option, the Engineer will determine if the non-compliant material will be removed. Table 504.02 Tolerances and Pay Factors Specified Property Tolerance Pay Facto r AASHTO T 59, Prior to Dilution, Residue after Distillation ≥ 56.0% 1.00 54.0% - 55.9% 0.85 52.0% - 53.9% 0.70 < 52.0% 0.40 or Reject Pay Factors for Tests for ALL other Properties Specified* 1.00 for deviation of ± less than or equal to 10% 0.75 for a deviation of ± greater than 10% to less than or equal to 25% 0.40 or Reject for deviation of ± greater than 25% * When the specification requirement is stated as a percentage, the test result deviation from the specification will be divided by the specification value. The resulting deviation percentage is then applied to the listed criteria. Note: When more than one specified property exceeds specification tolerances, the single largest Pay Factor Reduction will be the one applied.
3.When disputes arise in test resu lts, the Department will select an independent laboratory for referee test ing on the remainder of the sample. The identity of the independent labo ratory will not be revealed until the selected laboratory has completed the referee testing.
a.Only the Contractor can init iate dispute resolution, and request referee testing. Should the Contractor request referee testing, it shall be submitted in writing to the Departmen t within 4 days of receiving the notification of deficienc y. This written request is also affirmation and agreement that the testing may occur beyond the 14 day testing timeframe of the asphaltic emulsion specifications.
b.If the independent lab’s tests indicate failing results and pay deductions equal to or greater than the Department’s, the Contractor will reimburse the Department for the cost of testing. If the independent lab’s tests indicate that the material meets s pecifications or is at a pay deduction less than the Department’s, the Department will assume the cost of testing. Tack Coat 504.05 - 329 - When the independent lab’s tests indica te a pay deduction, the lesser of the Department’s and the independent la b’s deductions will be applied.
4.Water used to dilute emulsified asphalt is subsidiary to "Tack Coat" and is included in the solution that is placed and measured for payment.
5.Payment is full compensation for all work described in this Section. - 330 - SECTION 505 -- ASPHALTIC CONCRETE CURB
505.01 Description
1.This work consists of constructing asphalt curbs as shown in the contract.
505.02 Material Requirements
1.The curb will be constructed of the same type of asphaltic concrete mixture used in the surface course or a commercially available asphaltic concrete approved by the Engineer.
505.03 Construction Methods
1.Asphaltic concrete construction methods described in Section 503 shall also govern the construction of curbs.
2.The Contractor shall shape and compact curbs with a curb machine. Uniform density and smooth surface texture must be attained.
3.The Contractor shall clean a nd apply a tack coat to the contact surface. The tack coat shall be applied in accordance with the requirements of Section 504 and shall extend 4 inches (100 mm) beyond the curb contact surface in all directions. The rate of application shall be as directed by the Engineer. Heating the surface may be required to achieve a bond with the new asphaltic concrete. The heating shall be done so that no portion of the asphaltic concrete is damaged by excessively high temperatures.
4.The newly constructed curb and a 24 inch (600 mm) width of the adjoining surface (gutter) shall be sealed by the application of a tack coat. The rate will be determined by the Engineer.
505.04 Method of Measurement
1.Asphaltic concrete curb length is measured by the linear foot (meter).
505.05 Basis of Payment
1.P a y I t e m P a y U n i t Constructing Asphaltic Concrete Curb Linear Foot (LF) [Meter (m)]
2.Materials required to construct curbs are included in the pay items "Asphaltic Concrete, Type _____" and "Performance Graded Binder_____" of the surface course in Section 503.
3.Payment is full compensation for the work described in this Section.
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 361–363 of 1,048.