Additives add benefits

By Jeff Winke

Asphalt pavement sealcoats are commonly used for the protection and preservation of off-street asphalt surfaces such as home driveways, parking lots, airports, gas stations, and the like. Additives are specialty chemicals that are added to enhance the performance properties of sealcoatings.

“Many latex polymers have been used for specific purposes ever since the introduction of sealcoatings,” stated Girish C. Dubey, president, STAR, Inc., Columbus, Ohio. “Considering the myriad of such additives, it is imperative to understand the basic chemistries of such additives and recognize the ones that will truly enhance the performance of the sealcoating in terms of better flexibility, toughness, fuel and chemical resistance, and overall longevity. Sealcoating specifications, delineating the proper ratios of various components in the mix design are of critical importance for the optimum performance.”

The role of sealcoat additives becomes apparent when recognizing the limitations of asphalt.

“Asphalt has very poor resistance to weathering and is easily attacked by chemicals, gasoline, oils, fats and deicing salts,” Dubey said. “The elements of weather degrade the asphaltic oils from the surface and chemicals dissolve them away. With the loss of asphalt cement, the aggregates in the top layer begin raveling and develop the first sign of pavement deterioration; the appearance of minor surface cracks. With the progression of time, these cracks increase in number and size, and if not repaired, will allow water to penetrate sub-base and base layers. Saturated with water, sub-base and base courses lose their strength to bear traffic loads, develop larger cracks and eventually the pavement fails.”

Sealcoatings are commonly used as “barrier” coats to protect the asphalt from the damaging elements of weather, salt and chemicals. Contractors use additives to save time and to save money in the long run.

“Additives help to ensure better dry/cure the first time and help contractors avoid having to revisit job site,” stated Rick Poole, president, Diamond Shield Fortifier, Alexander, Arkansas. “Using sealcoat additives will allow jobs to open sooner due to faster dry/cure times. Increased film strength will cause coatings to perform longer over time and have an overall better appearance. Additives will also keep the sand load in suspension resulting in no sand bar in the bottom of an empty tank.”
Sealcoat additives add an important layer of flexibility to the sealcoating that can prevent cracking and other damage.

As a sealcoat additive, sand offers the following benefits:

• Minimizes the look of defects
• Provides skid resistance
• Minimizes sun glare, which can damage asphalt over time
• Provides greater durability and increased capacity to withstand large, heavy vehicles
• Helps solidify asphalt and fills in porous gaps for greater durability

Latex as an additive comes in a wide range of formulations, each of which have uniquely beneficial properties for your asphalt:

• Facilitates a speedier drying and curing time post application
• Noticeable results that can last a long time
• Latex gives your asphalt that desirable, clean black hue to keep it looking fresh and brand new
• Latex can provide adhesion to bond with the pavement

“The additives based on polymer/ rubber latexes are used to enhance the performance properties of sealcoatings and should be selected with the proper understanding of their properties and overall contribution to sealcoating longevity,” Dubey said. “Additives with poor resistance to destructive elements may actually cause premature failure. Additionally, mix designs must be formulated with proper understanding of the total solids and binder/ filler ratio. Additives will not remedy the deficiencies introduced by the excessive amounts of water or sand/aggregate.

“The proportions of various ingredients in the mix design, manufacturer’s recommendations and specification requirements are of crucial importance for the desired performance of a sealcoating job. A proper understanding of these principles is invaluable to the sealcoating professional.”

In general, sealing with additives provides benefits compared to sealing without. Additives are designed to enhance and strengthen the natural qualities of sealcoats by extending sealer durability and longevity. The principal benefits of the different asphalt sealcoat additives include faster dry times, better sand suspension, more flexibility of the final product, added durability, and altered viscosity.

As a final thought, here are a couple of sealcoating application tips for determining if a sealcoating job is ready for traffic that Poole offers based on his experience: “Two mini tests learned from years of sealcoating are the ‘10-minute floor mat test’ and the ‘20 steps and K-turn test’. Using a floor mat from your vehicle you can judge whether a parking lot is possibly too wet to sealcoat. Leave the floor mat laying on the asphalt for 10 minutes. If you see condensation when you lift the mat at the end of the time, then it is more than likely too wet or humid to sealcoat that day. The ‘20 steps and K-turn test’ is good way to judge if the sealcoat has dried/cured. Simple as it sounds, you walk about 20 steps across the lot and listen for the sticky sound that all contractors are all too familiar with when the sealcoat hasn’t dried/cured quite yet. If you don’t hear that sticky sound then drive down an aisle, pull into a parking stall, back out and proceed in the opposite direction. If there is no damage, then the lot is more than likely ready to open.

Jeff Winke is a business and construction writer based in Milwaukee, Wisconsin. He can be reached through jeff_winke@yahoo.com