Protecting asphalt pavement is one of the most cost-effective investments a property owner can make. Sealcoating extends the service life of asphalt by shielding it from sunlight, water, deicing chemicals, and petroleum spills. But not all sealers are created equal. The two primary options—refined coal tar sealer (RTS) and asphalt-based sealer (ABS)—offer fundamentally different performance profiles, safety considerations, and application characteristics. This guide breaks down everything contractors and facility managers need to know to make the right choice. For a deeper look at application techniques in demanding environments, see our guide on sealcoating busy commercial lots with high-traffic pavement maintenance strategies.
Understanding the Two Primary Sealer Types
Before comparing performance, it helps to understand what each product actually is and where it comes from. Both RTS and ABS serve the same fundamental purpose—protecting asphalt pavement—but their chemical origins lead to very different behaviors in the field.
What Is Refined Coal Tar Sealer (RTS)?
Refined coal tar sealer is manufactured from a selectively refined fraction of crude coke oven tar, which is a byproduct of the steelmaking process. The raw coal tar undergoes a distillation process to remove lighter compounds, yielding a stable, high-performance binder that exhibits exceptional resistance to petroleum products and environmental degradation. RTS has been used for decades and is manufactured to meet ASTM performance specifications, including ASTM D3323 and D4866. These standards ensure consistent quality, viscosity, and solids content across batches from reputable manufacturers.
A key advantage of the RTS manufacturing process is that it produces a chemically inert film once cured. This film does not soften or re-emulsify when exposed to gasoline, diesel, or hydraulic fluid—a critical property for parking lots, gas stations, truck stops, and any pavement that sees vehicle traffic.
What Is Asphalt-Based Sealer (ABS)?
Asphalt-based sealer, also called asphalt emulsion sealer, is made from a selectively refined fraction of crude petroleum oil—the same base material used to produce the asphalt pavement itself. The asphalt is emulsified with water and surfactants to create a stable, workable liquid that can be applied with spray equipment or squeegees. ABS products are generally less expensive than RTS and have a milder odor during application, which makes them popular for residential driveways and light commercial lots.
However, because ABS is chemically similar to the asphalt pavement it is meant to protect, it has an inherent limitation: it cannot resist fuels, oils, or solvents. These petroleum-based substances will re-emulsify and dissolve an ABS coating, leading to premature failure. Unlike RTS, there is currently no universally accepted ASTM performance specification for ABS formulations, which means quality can vary significantly between manufacturers. To better understand how different sealer chemistries affect long-term results, explore our detailed breakdown of sealcoating mix designs for long-lasting pavement protection.
Critical Performance Differences Between RTS and ABS
The performance gap between RTS and ABS is substantial and well documented. Contractors who understand these differences can specify the right product for each job and avoid costly callbacks.
Fuel and Chemical Resistance
This is the single most important differentiator. RTS forms a chemically cured film that is impervious to petroleum hydrocarbons. When a vehicle leaks oil or a customer drips gasoline onto an RTS-coated surface, the sealer remains intact. ABS, by contrast, is a re-emulsifiable product. Even minor fuel spills can soften, stain, or completely remove an ABS coating, exposing the underlying pavement to damage. For any commercial lot that experiences vehicle traffic, the fuel resistance of RTS is a decisive advantage.
Durability and Weather Resistance
RTS offers superior resistance to the natural aging process caused by ultraviolet radiation, rain, freeze-thaw cycles, and deicing chemicals. The refined coal tar binder does not oxidize as readily as asphalt, so RTS coatings retain their black color and protective properties longer. In northern climates where snow and ice are common, the combination of salt exposure and freeze-thaw action can degrade ABS coatings in as little as one to two seasons. RTS typically delivers two to three times the service life under identical conditions.
Adhesion and Cohesion Properties
RTS demonstrates stronger adhesion to the underlying pavement and stronger cohesive strength within the film itself. This means the sealer sticks better to the asphalt and holds together more effectively under traffic stress. The practical result is less scuffing, reduced tracking, and fewer delamination failures. ABS, while adequate for low-traffic residential settings, tends to wear more quickly in turning lanes, braking zones, and high-traffic entry areas where shear forces are highest.
- RTS adhesion: Bonds strongly to asphalt, resists peeling and delamination
- ABS adhesion: Adequate for light traffic, prone to wear in high-shear zones
- RTS cohesion: Tight molecular structure resists scuffing and tire pickup
- ABS cohesion: Softer film can show tire marking and tracking in hot weather
Safety, Regulations, and Environmental Considerations
One of the most debated topics in the pavement maintenance industry is the safety profile of refined coal tar sealers. Critics point to the presence of polycyclic aromatic hydrocarbons (PAHs) in coal tar, while proponents note that RTS has been used safely for decades with no documented cases of adverse health effects from properly applied sealer.
Understanding PAHs in Context
PAHs are a class of chemical compounds that occur naturally in coal, crude oil, and gasoline. They are also produced when wood, tobacco, or meat is burned. The presence of PAHs in coal tar has led some environmental agencies to classify coal tar as a potential hazard based on high-dose animal studies. However, the relevance of these studies to real-world sealer exposure is questionable. Sealer applicators and the general public are exposed to PAH levels many orders of magnitude lower than the doses used in laboratory animal tests.
What Regulatory Agencies Say
The U.S. Food and Drug Administration (FDA) lists coal tar as a generally recognized as safe and effective (GRASE) active ingredient for over-the-counter dandruff, psoriasis, and eczema treatments at concentrations up to 5 percent. Millions of people use coal tar shampoos and creams daily with no documented cancer risk. Studies of occupational cohorts—including roofers, pavers, and sealcoating applicators—have not found elevated cancer rates attributable to coal tar exposure. Independent epidemiological reviews consistently conclude that there is no evidence linking intermittent, low-level coal tar exposure to cancer in humans.
That said, contractors should follow best practices regardless of which sealer they choose:
- Wear appropriate personal protective equipment including gloves and safety glasses
- Use proper ventilation when applying sealers in enclosed or semi-enclosed areas
- Follow manufacturer guidelines for mixing, application, and cleanup
- Dispose of wash water and residue according to local environmental regulations
Selecting the Right Sealer for Your Project
Choosing between RTS and ABS comes down to matching the product to the specific demands of the site. The table below summarizes the key differences at a glance.
| Property | Refined Coal Tar Sealer (RTS) | Asphalt-Based Sealer (ABS) |
|---|---|---|
| Fuel and oil resistance | Excellent | Poor |
| UV and weather resistance | Superior | Moderate |
| Service life (typical) | 3 to 5 years | 1 to 3 years |
| Adhesion to asphalt | Strong | Adequate |
| Cost per square foot | Higher | Lower |
| ASTM specification | Yes (D3323, D4866) | No universal spec |
| Odor during application | Strong | Mild |
| Best application | Commercial, industrial, fuel-heavy sites | Residential, light-traffic areas |
When Refined Coal Tar Sealer Is the Best Choice
RTS is the preferred sealer for most commercial and industrial applications. Gas stations, convenience stores, truck stops, auto repair shops, fast-food drive-throughs, and shopping center parking lots all benefit from the fuel resistance and long service life of RTS. Property owners who want maximum return on their pavement maintenance investment and are willing to pay a premium for superior performance should specify RTS. Contractors who build their reputation on quality work also prefer RTS because it delivers consistent, durable results that minimize callbacks. For those new to the sealer market, our guide on asphalt emulsion sealers and what contractors need to know about pavement protection provides additional context on how these products compare in real-world conditions.
When Asphalt-Based Sealer Makes Sense
ABS is a perfectly adequate choice for residential driveways, light-use municipal lots, and paved surfaces that see minimal vehicle traffic and no fuel exposure. The lower material cost, milder odor, and water-based cleanup make ABS more accessible for DIY homeowners and small contractors working on tight budgets. However, it is important to set realistic expectations: an ABS coating will need more frequent reapplication and will not protect against petroleum stains. If a customer parks a leaking vehicle on an ABS-coated driveway, the result will be an unsightly stain that cannot be removed without recoating. For seasonal pavement care, our article on why asphalt cracks and potholes form in winter and how to restore pavement in spring offers practical advice for maintaining pavement integrity year-round.
Application and Curing Considerations
Both sealer types require careful attention to application conditions for optimal results. The pavement surface must be clean, dry, and free of debris. Cracks should be filled and potholes repaired before sealcoating begins. Temperature is critical: most manufacturers recommend applying sealers when ambient temperatures are above 50 degrees Fahrenheit and rising. RTS generally requires a longer curing time than ABS before the surface can accept traffic, typically 12 to 24 hours depending on weather conditions. ABS may cure faster, sometimes accepting light traffic within 4 to 8 hours, but the film remains softer and more susceptible to damage for several weeks.
- Prepare the surface: clean, crack-fill, and patch before sealing
- Check weather: no rain expected for 24 hours, temperatures above 50 degrees F
- Apply evenly: use spray equipment for large areas, squeegee for small lots
- Allow proper cure: RTS needs 12-24 hours, ABS needs 4-8 hours before traffic
- Apply two coats: optimal protection comes from two thin coats rather than one thick coat
Both refined coal tar sealers and asphalt-based sealers have their place in the pavement maintenance industry. The key is matching the right product to the right application. For commercial lots with fuel exposure, high traffic volumes, and a need for long service life, RTS is the clear winner. For residential driveways and budget-sensitive light-duty projects, ABS offers an affordable alternative. Understanding these differences allows contractors to deliver the best value to their customers and build a reputation for informed, professional service.