Asphalt Ingredients

This type of sealant is entirely synthetic, made of polymers and acrylic. While more expensive than either coal tar or asphalt sealers, acrylic sealers do not have the drawbacks of either and have the added benefit of coming in several colors for aesthetic appeal.

This sealer is asphalt-based, easy to apply, and tends to produce fewer harmful volatile organic compounds than coal tar sealers, making them more environmentally friendly. The drawbacks of this type of sealer, however, are its relatively higher price and its tendency to degrade more quickly than coal tar sealer — the average asphalt-sealed driveway tends to deteriorate to the point of needing replacement after about two years of exposure to the sun, moisture, and automotive chemicals.

Some sealants are blends that contain both coal tar and asphalt. The ratio of products determine the properties and uses of these sealants. A blend with a larger ratio of coal tar will behave more like coal tar sealer and vice versa. The usage of such combinations helps control some of the environmental issues associated with coal tar without seriously compromising its more desirable qualities. The primary difference with such blends is that curing takes longer for blends than for pure asphalt or pure coal tar sealers because particles of tar and asphalt don't coalesce as quickly as pure emulsions.

One of the most common types of sealer, coal tar sealants are made with a combination of coal tar, sand, clay, and additives. Easy to apply and very resistant to the elements, coal tar sealers are highly durable and last well for several years. This sealer is also very affordable and stands up against gasoline and chemical spills, sunlight, and intense weather. The primary drawbacks to this type of sealant, however, include its smell, environmentally harmful runoff, and potential for causing skin irritation.

These sealers are used for smaller cracks in driveways as a way to minimize damage. It comes in many varieties, but crack filler sealer is primarily available in hot-applied or cold-applied versions — the former is applied by heating the material with a torch as it is applied, while the latter can be applied without heat using a caulking gun. Typically, these are temporary fixes until more durable sealers are applied.

Epoxies are significantly more expensive than most other options, but are gaining popularity in use on both garages and driveways. This durable coating helps protect driveways from the elements and reduces the tendency for concrete to crack following dramatic temperature fluctuations.

Linseed oil is one of the earliest concrete sealers available, effective at preserving and protecting concrete driveways without the negative environmental issues associated with ordinary oil-based sealers.

With grease or petroleum as a primary ingredient, oil-based sealers are highly resistant to the elements and last significantly longer than water-based sealers. The drawback is their emission of more volatile organic compounds (VOCs), which can be both an environmental and health hazard.

Water-based sealers are precisely what they sound like — they are primarily made of water-dispersible resins protectants. While this quality makes these sealers more environmentally friendly, they are not as durable as other sealers.

Refined coal tar-based sealers are emulsions that primarily consist of coal tar, pure water, emulsifying agents, and additives.

• Coal tar: Coal tar is a refined form of a byproduct called coke oven tar, which is a residue left after the distillation of oils for use in industrial and consumer manufacturing. This pitch is refined and separated into 12 grades of viscosity, which are each used in different industries, like the aluminum and steel industries. The most viscous category is RT-12, which is used in the production of coal tar sealcoat.
• Emulsifying agent: Also known as the surfactant, the emulsifying agent is a water-soluble, soap-like substance that consists of an ionic head and a hydrocarbon tail. These molecules surround coal tar particles and give them an electric charge, causing them to repel each other and stay suspended in water.
• Additives: Coal tar sealant concentrate is usually mixed with sand, clay, and polymer additives to improve its durability and ease of application. Because all coal tar sealers are regulated and produced to meet federal specifications , the mixture of these additives is what professionals primarily use to achieve different sealant results.

After mixing the concentrated coal tar emulsion with water and additives , the slurry is applied to the driveway surface in an even coat. After application, the emulsifying agent destabilizes, and the water evaporates, allowing the particles in the slurry to bond and form a solid film. Coal tar sealants typically take a few hours to dry, but a quality coat can last up to five years due to coal tar's natural resistance to light, heat, and automotive chemicals.

Asphalt-based sealers are asphalt emulsions that primarily consist of asphalt, pure water, and an emulsifying agent.

• Asphalt: Asphalt is a selectively refined form of crude petroleum oil and makes up about 50 to 75 percent of a typical emulsion. Asphalt tends to be slightly more variable than coal tar in its production, meaning that different refineries will produce asphalt with different properties, which can affect the viscosity of the sealant. Additionally, since asphalt is petroleum-based, it is chemically similar to petroleum-based automotive fuels and fluids — this means that asphalt is, by definition, not resistant to fuel.
• Emulsifying agent: While these emulsifying agents achieve the same result as those used in coal tar emulsions, emulsifying agents used in asphalt tend to differ based on the compositional differences and chemical properties of the asphalt being used. While coal tar is standardized, asphalt is more variable. Emulsifying agents are employed for chemical compatibility to create a stable emulsion.
• Additives: The most common additives for asphalt emulsions are polymer and non-polymer sealants. Typically, the additive used is either a waterborne acrylic resin or waterborne vinyl — the local environment and temperature gradients will determine which type is used in the final mixture. Mixing additives should be done very carefully, however, since asphalt-based sealers are not standardized and may contain chemicals that are incompatible with certain types of additives. For example, an asphalt emulsion made with an anionic emulsifying agent cannot be mixed with a cationic polymer emulsion, or else the emulsifying agents will gel (ionic bonding) and negate the beneficial properties each produce in ionically balanced mixtures.

After mixing in additives and diluting with water, the sealant mixture is applied to a surface in a slurry, allowing the asphalt and any added particles to spread evenly across the surface. At this point, the emulsifying agent destabilizes, allowing the asphalt and additives to bond as the water evaporates. Asphalt emulsions typically take eight hours or more to dry, depending on the water content and weather.

The important performance assets to remember with asphalt are that it is more thermoplastic, yet more susceptible to humidity, compared to coal tar. Due to its chemical composition, asphalt requires higher temperatures to become fluid than coal tar sealers, requiring heat application at temperatures above 50°F. If the temperature drops below this threshold, the asphalt will remain solid and will not form a proper film, resulting in an ineffective seal. Additionally, it should only be applied in dry weather — rain and humidity can prevent the asphalt from forming a consistent film.

Even after application, asphalt-based emulsions tend to be more susceptible to changes in the temperature and weather. This, along with asphalt's natural susceptibility to automotive fluids, means that asphalt should be reapplied every two years.

Asphalt and coal tar emulsions are usually sold in either ready-to-use or concentrate forms. Ready-to-use forms are pre-mixed and have water added to form a thick slurry. Concentrate forms, however, are commonly used in construction applications requiring the addition of water and additives to achieve a final result. Here are some of the additives commonly used in sealant mix design along with the benefits they provide:

• Sealing additives: Polymers and non-polymer sealers are often added to asphalt emulsions as the active sealing ingredient, but may also be added to coal tar emulsions. This addition brings strength, elasticity, and durability to the sealant. These are often added as emulsions to ease the mixing process.
• Aggregates: Sand, aggregate or boiler slag is a common addition to sealant mixtures, added at a rate of two to five pounds per gallon of concentrated sealer. Aggregates of any type help improve dry time, skid resistance, and wearability while also filling in surface defects and creating a uniform texture on driveways.
• Water: While simple, water is an essential ingredient in the sealant mix, imparting proper flow and leveling for the sealant. Typically, asphalt emulsion sealants are diluted up to 25 percent while coal tar emulsions can be diluted more.

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