Prime Coat/Tack Coat PRIME COAT/TACK COAT
Part 1 — General
1.1 Section Includes
A.Materials and procedures for applying prime and tack coat.
1.2 Related Sections
A.Section 02745: Asphalt Material
1.3 References
A.AASHTO M 82: Cutback Asphalt (Medium -Curing Type)
B.AASHTO M 208: Cationic Emulsified Asphalts
C.AASHTO T 27: Sieve Analysis of Fine and Coarse Aggregates
D.AASHTO T 201: Kinematic Viscosity of Asphalts (Bitumens)
E.ASTM D 5095: Determination of the Nonvolatile Content in Silanes, Siloxanes and Silane- Siloxane Blends Used in Masonry Water Repellent Treatments
1.4 Definitions
A.Emulsified Asphalt – A group of asphalt products using water and soap (emulsifier) to reduce viscosity. These products consist of approximately 60 percent asphalt and 40 percent emulsifier.
1.Undiluted - No additional water has been added to the emulsion
2.1:1 Dilute - One part emulsion to 1 part water
3.2:1 Dilute – Two parts emulsion to 1 part water
B.Prime coat – Liquid asphalt applied to a prepared subgrade.
C.Tack coat – Emulsified asphalt to the existing surface or new pavement surface and intermediate lifts. Prime Coat/Tack Coat
1.5 Submittals
A.Material invoice or bill of lading for information.
B.Prime coat/tack coat work plan for review.
1.Include quantities, rate of application, temperatures and areas to be treated.
2.Refer to this Section , Article 3.2 for application rates.
C.Request to dilute emulsified asphalt for approval.
Part 2 — Products
2.1 Prime Coat
A.MC-70 or MC -250. Refer to AASHTO M 82.
1.Do not dilute .
2.2 Tack Coat
A.CQS -1h or CSS -1h emulsified asphalt . Refer to AASHTO M 208 and Section 02745.
1.Use specified emulsion or s elect emulsion according to the time constraints required for Maintenance of Traffic (MOT ) and the ability to fully cure before allowing traffic on the tack coat .
a.A diluted product may be used to better control distribution when the residual application rate is small (0.03 gal/yd 2).
b.Dilute at terminal only.
c.Do not change dilution before obtaining approval from the Engineer.
2.A cationic organosilane additive with a minimum nonvolatile content of 38 percent may be used. Refer to ASTM D5095
a.Use a dosage from 0.7 percent to 1.0 percent by weight of the emulsion.
b.Modify the emulsified as phalt requirements to m eet a maximum cement mixing test of 10 percent.
2.3 Blotter Material
A.Granular material meeting Table 1. Refer to AASHTO T 27. Prime Coat/Tack Coat Table 1 Granular Materials Sieve Size Percent Passing No. 4 No. 10 No. 200 90 to 100 25 to 80 0 to 15
Part 3 — Execution
3.1 Surface Preparation
A.Prime Coat
1.Verify the base material meets all contract requirements prior to placement.
2.Clean the surface of all materials that prevent bonding to the existing surface.
B.Tack Coat
1.Clean the surface of all materials that prevent the tack coat from bonding to the existing surface such as mud, dirt, and leaves .
3.2 Application
A.Use a pressure distributor to apply the asphalt in a uniform, continuous spread.
1.Keep the viscosity between 50 and 100 centistokes. Refer to AASHTO T 201.
B.Apply prime coat according to the authorized work plan to prepared grade at an application rate of 0.5 gal/yd
1.Spread blotter material if the prime coat does not penetrate.
a.Use the quantities required to absorb the excess asphalt.
2.Keep construction traffic off the prime coat until it has cured and dried.
C.Apply tack coat according to the authorized work plan between all lifts of Asphalt Mix and to all surfaces, including vertical that will come in contact with Asphalt Mix.
1.Meet the residual application rate shown in Table 2.
a.Undiluted, 1: 1 Dilute and 2:1 Dilute application rates shown are based on 60 percent residual asphalt. Prime Coat/Tack Coat
b.Adjust application rate if emulsion is not 60 percent residual asphalt to achieve required residual rate.
c.Adjust application rates according to field conditions.
2.Cover all tacked surface areas with surfacing materials the same day the tack coat is applied. Table 2 Application Rate (gal/yd2) Existing Pavement Condition Residual Undiluted 1:1 Dilute 2:1 Dilute New Asphalt Mix 0.03 0.05 0.10 0.08 Oxidized Asphalt Mix 0.05 0.09 0.18 0.13 Milled Asphalt Mix 0.07 0.12 0.24 0.18 Milled PCC P 0.07 0.12 0.24 0.18 PCC P 0.05 0.09 0.18 0.13
D.Do not apply prime coat or tack coat:
1.On a wet surface or where surface conditions prevent proper adhesion.
2.When the surface temperature is below 50 degrees F.
3.When weather conditions prevent proper adhesion.
E.Protect all structures including items such as guardrails and guide posts from being spattered or marred.
Source: Utah Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 531–534 of 1,331.