Introduction

Of all the calls we get from Texas contractors, questions about hot applied AC grades and trackless tack materials come up more than anything else. Usually the conversation goes one of two ways: either a contractor has a TxDOT spec calling for PG 64-22 or AC-20XP as a tack coat and wants to know if our distributor can run it, or they've heard about trackless tack and want to know how it works and what equipment it needs.

Both materials do the same basic job — bonding a new asphalt layer to an existing pavement surface — but they do it very differently from conventional emulsion tack coats. Understanding those differences matters before you call a distributor rental company.

What Is Hot Applied Tack Coat?

Conventional tack coat is an asphalt emulsion — asphalt binder mixed with water and an emulsifying agent. It applies at ambient or low temperatures, the water breaks out and evaporates, and what's left is the binder residue that bonds the layers together. SS-1H and CSS-1H are the standard workhorses for most Texas overlay tack coat applications.

Hot applied tack coat skips the emulsion process entirely. It's straight asphalt binder — either an AC grade or a Performance Grade (PG) binder — applied directly at high temperature, typically between 275°F and 375°F depending on the grade. There's no water content, no break time waiting for water to evaporate, and the bond is often stronger and more immediate than emulsion tack.

TxDOT Reference

TxDOT's Asphalt Binder Selection Guide lists PG binders as a standard tack coat material alongside emulsions like SS-1H and CSS-1H, all governed by Item 300, "Asphalts, Oils, and Emulsions" (2024 Specifications).

Common hot applied tack materials specified on Texas projects include PG 58-22, PG 64-22, AC-10, AC-15P, AC-20XP, and polymer-modified grades like AC-10-2TR and AC-20-5TR.

What Is Trackless Tack?

Trackless tack — sometimes called non-tracking tack coat — is a relatively recent category of material developed specifically to solve one of the most frustrating problems on overlay jobs: conventional tack coat sticking to truck tires and being tracked away from the pavement surface before the overlay is placed.

Trackless tack is a hot-applied binder — usually a stiff-residue or soft-residue modified AC — that sets up quickly after application, loses its tackiness on the surface, but reactivates under the heat and pressure of the overlay being placed. The result is a material that trucks, pavers, and rollers can drive over without tracking, while still delivering a strong interlayer bond once the hot mix is placed.

TxDOT Research

TxDOT-sponsored research through the Texas A&M Transportation Institute (Project 0-6814) evaluated trackless tack products in Texas, assessing tracking resistance, bond strength, and performance to develop specifications. TxDOT's 2024 Item 300 specifications define NT-HA1 as a Non-Tracking Hot Applied Tack Coat — a TRAIL product — within the approved asphalt materials list.

How They Compare to Conventional Emulsion Tack

The practical differences matter for equipment selection. Here's a direct comparison:

Property Emulsion Tack (SS-1H / CSS-1H) Hot Applied AC / PG Trackless Tack
Application Temp Ambient – 160°F 275°F – 375°F 300°F – 375°F
Break / Set Time Requires break time — water evaporates Immediate — no water content Fast set — reactivates under overlay heat
Tracking Risk Stays tacky until covered Stays tacky Minimal — can be driven over
Typical Rate (residue) 0.03 – 0.10 gsy 0.02 – 0.05 gsy 0.02 – 0.05 gsy
Standard Distributor Compatible Not Recommended Not Recommended
Equipment Required Standard emulsion distributor High-temp configured distributor High-temp configured distributor

Why Standard Distributors Aren't Configured for These Materials

This is the question behind most of the calls we receive — and the answer is straightforward.

A standard Etnyre Black Topper configured for emulsion and cutback applications is engineered to operate reliably in the 120°F to 260°F temperature range. The heat system, pump seals, spray bar assembly, and nozzles are all specified and maintained to that operating range. Running hot applied AC grades and trackless tack materials at 300°F to 375°F pushes every one of those components well beyond their design envelope.

The specific risks are spray bar seal failures, pump seal degradation, nozzle damage from thermal expansion, and compromised tank insulation over repeated high-temperature cycles. These aren't theoretical — they're predictable outcomes when equipment is operated outside its rated range.

Distributors configured for hot applied AC and trackless tack require higher-temperature-rated heat systems, pump seals, and spray bar components. These are purpose-built configurations, not a standard rental fleet unit.

⚠ Important

If your project spec calls for PG binders, AC grades, or trackless tack operating above 275°F, our standard fleet is not configured for those applications. We'll tell you that directly rather than put equipment on your job that isn't built for the material. Call us before you commit to a material — it's a much easier conversation at the planning stage than after a spray bar failure on the road.

What TxDOT Allows for Tack Coat

This is worth knowing before you finalize your material selection. TxDOT specifications for tack coat allow CSS-1H, SS-1H, or a PG binder with a minimum high-temperature grade of PG 58 — giving contractors flexibility in material selection when the engineer approves.

In other words, on many Texas overlay projects you are not required to use hot applied PG binder for tack coat. Emulsion alternatives are often acceptable and should be confirmed with the project engineer before you commit to a material that requires specialized equipment.

Key Takeaway

TxDOT's Seal Coat Manual — Section 2, Selection of Binder confirms that for tack coat applications, acceptable materials include PG binders, CSS-1H, EAP&T, and TRAIL — meaning emulsion-based options are explicitly listed alongside hot applied binders. Confirm with your project engineer whether an emulsion alternative is permitted before booking equipment.

The TRAIL and EAP&T Options

Two materials worth knowing about for Texas contractors working on projects where conventional emulsion tack isn't meeting spec requirements:

EAP&T

Emulsified Asphalt Prime and Tack is a TxDOT-specified emulsified product that functions as both a prime coat and a tack coat. It applies at lower temperatures than hot AC grades and is compatible with standard emulsion-configured distributor equipment. A useful option when your spec allows it and you want to avoid high-temp equipment requirements.

TRAIL

TRAIL is TxDOT's designation for approved trackless tack products. TxDOT's 2024 Item 300 specifications include NT-HA1 as the non-tracking hot applied tack coat within the TRAIL product category. TRAIL products require hot-applied equipment. Confirm with your district materials engineer which TRAIL products are approved for your project before booking any equipment.

Questions to Ask Before Your Job

If your project involves tack coat and you're unsure about material and equipment requirements, work through these questions before you call a rental company:

1. What does your spec actually require? Check whether it mandates a specific material or whether alternatives are permitted with engineer approval. Many specs list emulsions as acceptable alongside PG binders.

2. Is the spec a TxDOT standard spec or a project-specific special provision? Special provisions sometimes require specific materials with no alternatives. Standard specs typically allow engineer discretion.

3. Have you confirmed with your district materials engineer? TxDOT district engineers have latitude to approve alternative materials. A quick call to your district can open up equipment options that make your job simpler and less expensive.

4. What equipment does your material supplier recommend? Your emulsion or AC supplier knows what their product requires. Call them before you call the rental company.

Further Reading