Knowledge Base

Sealcoatings have been an indispensable part of asphalt pavement maintenance programs for the past 6 decades; therefore, it is logical for the sealcoating professionals to have an insight into the basics of their composition, manufacturing and properties. Sealcoatings are specialty coatings, which are used for the protection and preservation of asphalt surfaces. They act as a true “Barrier coat” between asphalt surfaces and the destructive elements that attack those surfaces (mainly the sun’s ultraviolet rays, gasoline, oils, salts, grease/fats, etc.). The very term "sealcoating" means keeping the redeeming properties of asphalt (like waterproofing and flexibility) sealed in so as to prolong the pavement life and preserve its functional properties. After all, your pavement is a sizable investment and it has been technically acknowledged that Sealcoating extends the life of a sound pavement by more than 300%, at 1/3rd the cost of pavement replacement.

In appearance, sealcoatings are thick semi-fluid (like house paints), dark-chocolate brown colored, water based coatings. They are essentially fine dispersions of binders (commonly refined tar or asphalt), clays, fillers, and specialty chemicals in a medium of water. The four major components in sealcoatings are described below:

Binder - It is the backbone of sealcoating compositions, the component that is responsible for imparting protection, preservation and beauty, while bonding tenaciously to the asphalt pavement.
Clay and Fillers - impart tensile strength, hardness and abrasion resistance. Selection of the right clays and also regulating the amount of those fillers are imperative to maintain the proper balance between the toughness and flexibility of the sealcoating for its proper functioning.
Water - is the medium in which all the ingredients stay stably dispersed and is the reason for a sealcoatings ease in handling, application and storage.
Specialty Chemicals - are added to perform specific functions e.g. water repellency, flexibility, specific resistance to salts and petrochemicals, while also maintaining the physical stability of the sealcoating.

Refined Tar Based sealcoatings (RTS) are based on RT-12, a highly refined grade of coal tar, which, in turn is generated during the conversion of coal into coke for steel metallurgy. RT-12 is composed of numerous very stable chemicals that are not affected by the destructive elements of weather, sun’s ultraviolet rays (UV), salts, gasoline, oils, fats and other petro-chemicals. RTS has been the workhorse of the industry for several decades and their properties and compositions are fully delineated in many specifications.
Asphalt Emulsion Based Sealcoatings (AE), are based on asphalt and are formulated either using hot asphalt (AC) or pre-emulsified asphalt. AE coatings originated on the west coast, primarily this was due to the unavailability of refined tar in that area. Coal and steel mills were primarily located east of the Rockies. Although the AE based sealcoatings generally lack resistance to petro-chemicals (gasoline, oils, fats, etc.), they work very well in maintaining the surface integrity of asphalt pavements and keep cracks from appearing. Over the years, the performance of AE coatings has been fortified with chemicals and specialty rubber polymers to enhance their overall performance.

How are the sealcoatings made?
There are two commonly used methods for manufacturing sealcoatings, Both methods yield sealcoatings with comparable performance properties.
The Batch Process involves adding formula ingredients individually in the right sequence and grinding them into a fine dispersion in a high-speed disperser (HSD). The major benefit of this process is the excellent control over the processing and the quality of the sealer.
The Continuous Process or Colloid Mill Process involves feeding a continuous stream of materials into the mill where they are subjected to a grinding action much like a flour mill. This process requires highly skilled batch operators to achieve batch-to-batch consistency. The major benefit of the Colloid Mill process is the high production rate.

Important Notes: 
Sealcoatings shall be applied to sound, properly constructed asphalt pavements that are free from defects, according to manufacturers or project engineers detailed instructions.
Meet all applicable specifications; FAA, ASMA, ASTM D-5727-00 (Formerly Federal Specification RP-355e), and commercial specifications.
The Applicator must read the safety data sheet on the products and observe all precautions for both personal and environmental safety.
NEVER allow uncured sealer to be washed into the bodies of water. Washings from all tools and equipment shall be collected and disposed off according to applicable local, state and federal regulations.

Why Surface Preparation and Priming Is Important:
Why bother cleaning the asphalt...?  Because a sealcoating application will NOT stick if the surface is not properly prepared and YOUR reputation will likely suffer if the job doesn't perform as promised!  It doesn't matter what type of coating or mix design – If the asphalt surface isn’t clean – It ain’t gonna stay.

Why Asphalt Sealer Sticks or Doesn't Stick to a Surface.
Knowing when NOT to sealcoat could be one of the keys to your success. A good understanding of asphalt surfaces themselves, sealcoatings and why they work, the affects climate has on the cure process, and generally, best practices for preparing the surface to accept the sealcoating will help you know when, and when not to do an application.

You should understand how to do a "water break free" test on newer asphalt pavement surfaces. Conversely, you should know when an asphalt pavement surface is too old and badly oxidized, or the aggregate is too polished, to allow the coating to properly adhere to the surface.

Climate will play a big role in the success of the final product and a good applicator will be able to communicate the impact that inclement weather will have on a job.

Know your site and the things that might trip you up.
Being a manufacturer myself, I have the unique position as being the sounding board for applicators whom are complaining about a job, or telling me stories about something that they had to do to overcome a bad situation. So I have heard all kinds of horror stories about things that have tripped up applicators. Some of the more obvious are:
 •  Forgetting to have the sprinklers shut down on the property - Have it understood with you client that sprinklers on the property should be SHUT-OFF 2 days prior to the application & they should be kept OFF for 2 additional days AFTER you are done with the Job. I STRONGLY recommend that you address the sprinkler issue in the contract!! Maybe something along the lines that if this Does Not get addressed – Additional Mobilization Charges may apply – Then let them know how much those charges are – That additional expense above & beyond the contract May just be the thing that Clicks in their mind that This Is IMPORTANT!
 •  Proper Site Survey - Not doing a proper site survey and finding a lot more work than you intended when you get there can kill your profits or could influence your judgment and lead you down a path that cuts corners and could hurt your reputation. With today’s technology - many people sit back in their office and use Google Earth to assess a property for a proposal – remember Google Earths' maps may be several years old and may not show the true, current condition, of the site. Proper planning is yet another key to your success.
 •  Not paying close attention to the weather and the potential for rain - There are more horror stories pertaining to weather than about anything else I get to hear. A rain event within a few minutes, or even a few hours can lead to disastrous results. Environmental concerns, sealer splashing up onto buildings and cars, and ultimately premature failure of the coating itself are some of the bigger issues a rain event can cause. Pay extra attention to the days weather forecast, and get an app for your smart phone that has a weather radar feature, that way you can see what's coming in real time.
•  Landscaping and edging issues - If you go to the site - which you all should be doing - check the asphalt edge on the lot for overgrown grass or any serious amount of sand, dirt, or muck built-up. Bring these issues to the attention of your client and ask them to have their lawn maintenance service address this issue before you arrive to do the job. Your talking to the customer about the issue early, will avoid surprises should there be an issue the day you show up to do the application.
•  Tree sap - Yes, tree sap. If the lot is lined with trees or there are trees overhanging the asphalt surface then you might see problems down the road that are unexpected. Things like the sealcoating flaking off and general adhesion problems that are uncharacteristic of your normal applications. Tree sap is one of those things that gets overlooked. Trees like olive, maples or pines on the site can cause sap problems. Trees can leave a fine mist of little sap particles onto the asphalt surface. This one has baffled more than a few people. Sap will cause the sealer to release from the asphalt surface. If you have visible tree sap on the lot it will have to be power washed off, or primed much like an oil spot.

The Mechanics of Site Preparation
Lets get into the mechanics of preparing your site now that we have laid the proper foundations for a successful job site survey.
SURVEY - Take a good look around and assess the work to be done vs. the instructions you have from the job costing bid. If you see something that is unexpected and will likely cause a problem - deal with that immediately. Call the dispatcher or your office and tell them immediately that something is not as it was supposed to be. If you are an independent - then immediately contact the client and tell them that things are not as initially quoted and an adjustment will need to be made.
MOISTURE - Is the pavement properly dry? You might show up while sprinklers were just on or maybe right after a rain event, and there is visible water on the asphalt surface. You are going to need a good blower and a squeegee or brush to move the water around, and then allow the asphalt surface sufficient time to dry as much as possible. You need to wait until the surface is visibly dry and there is no water ponding on the surface. Too much moisture held in the surface will DEFINITELY interfere with your coating being able to cure & maintain it’s longevity and this will likely result in tracking or a failure of the coating to bind properly!
ASSESS - Think about where you will start the work and where you will end up when you are finished. No sense moving around too many times and wasting time and energy. Beware of working yourself into a corner, don't laugh, it has happened to some people! Spend a minute planning your movements with your crew and make sure they are all on the same page. DON'T OVER LOOK SAFETY for your crew - Before any work begins you should make sure they ALL have the necessary protective gear available to them and that they are using that gear. Lastly make sure the site is secured, traffic is properly controlled, and no one can mistake that the area is actually closed off to car and foot traffic.
REPAIR - Address the cracks and potholes. Cleaning and treating the cracks can be accomplished while the rest of the lots surface is being cleaned and swept. Hitting these areas right away will allow the crack filler proper time to cure before you begin the process of sealcoating. Having sufficient people in your crew to do these kinds of things simultaneously will make the time on the property much more efficient.
TREAT - Oil-Spot Primer - A seal coaters best friend. You should always have a ready-to-use oil spot primer on your truck. This stuff can cure all sorts of pavement surface issues. Of course the main purpose of a primer is for oil spots, but it works wonders on other issues. After the pavement around a spot has been properly cleaned (broomed & blown off) apply primer on any oil spots or other areas that have been discolored or stained. Cut in entrances, exits and cul-de-sac’s with primer to insure the sealcoating properly bonds to the polished aggregates in that area.
CLEAN, CLEAN, CLEAN - Get a hand-held edger, a weed eater, good high powered blower and Git-Er Done! You have got to spend the time to broom & blow off ALL of the dirt, sand and debris on the asphalt. Not just the stuff you can see on the top of the surface, you got to get down into the profile of the asphalt where the dirt is stubborn and hides between the stone in the asphalt. Definitely have every inch of the asphalt hit by a brush and the blower. You may have to get a wire broom out & hit the difficult spots. And, don't forget the corners & behind the car stops. If you have the man-power you should have one guy brooming and brushing and the other guy operating the blower & blowing the debris out of the way. This is also where you might have to do the landscape edging where the grass meets the lot. Nothing looks worse then what happens after the coating is applied over grass that has been edged AFTER you leave.

Yes, we know it is HARD work, but it has to be done! Failing to do this step properly can lead to disastrous results. Any sealcoating you lay down will stick to what ever it is applied to, and if that material is dust and dirt, not the asphalt surface itself, then it will lift right up as soon as it is disturbed

READY FOR APPLICATION - After all this preparation work your crew will welcome the opportunity to finally get to the sealcoating step! Even though the reason you are on the lot is to apply a sealcoating, it is the preparation that makes or breaks the final success of the job you are doing. Skimp on any of the preparation steps and you will likely pay a price for it after you are done and gone. The companies who have been around for years, the ones with the best reputations, know this well and their work reflects it… So does their customer loyalty for that matter!

If you chose not to do these things properly then you can expect a decrease in longevity of the coating you just applied. You will likely have an unhappy customer, potentially a call back to the site – which ultimately will come out of the bottom line – and that means less money in YOUR pocket.  For the extra few minutes you spend doing it right – doing it wrong can cost you a lot more.

The list of positive results is much shorter - but positive results make you more money in the long run. A quality job with a happy customer, in this current economical climate is tremendously important. Do these things to stay financially viable for your family and the families your company supports. Be known in your area as The BEST! And remember, keeping an existing customer is a heck of a lot cheaper than trying to get a new one!

The very basic requirement for a sealcoating to bond firmly to an asphalt surface is that the surface shall be sound, dry, clean, and have an acceptable degree of surface profile.

What is Surface Profile?
Surface profile simply means if the surface is smooth, rough or in between. The surface profile of a pavement depends on; The pavement mix design. The type and quantity of the asphalt binder (AC type) The type of the aggregate used in the mix design. Coarse aggregates produce a rough profile and finer aggregates produce a denser and smoother profile. 

The paving method and the time of the year may influence the profile as well. For example the surface may look too coarse or irregular if; the roller compaction were inadequate or the weather was too cold for the proper knitting of the aggregates under the roller compaction.

Previous sealcoatings and the frequency of sealcoating. Sealcoatings fill the surface profile of the asphalt pavement and make them uniform. The use of sand in sealcoating mix designs is a common practice to impart a uniform textured appearance to the surface.

Why does the Sealer fail prematurely, in some areas?
It is understandable that sealer will not last as long in high traffic areas as in low traffic areas. It has, however, been noticed that sealcoatings may wear out prematurely in some areas that handle steady traffic e.g. traffic lanes, exits, entrances, etc. Sealcoating may be gone from such areas, in a matter of months.

If the overall surface profile was also proper at the time of the application then what caused the failure?
In most instances the failure is due to the loss of adhesion of the sealcoating from the top of the aggregates that become polished (smooth as glass) on the top. Such aggregates are called “Polished Aggregates” and they are too smooth on the surface to bond to the sealcoating. It is just like painting a mirror. All coatings need a certain degree of surface profile of the substrates to establish bonds.

In addition to traffic frequency, some aggregates are easily polished under normal traffic and are generally not used for paving. Their use in paving can potentially increase slipperiness. That is the reason why only "non-polishing aggregates" are used for road paving. It would be a good idea to check if the right type of aggregate was used on the problematic asphalt surface.

What to do for polished aggregates?
Roughen the surface by sand blasting, grinding or extensive wire brushing.  These may be too expensive and time consuming.

Prime the areas of high traffic (drive lanes, exits, entrances, etc) with a specialty primer that will soak into the aggregate and bond to the surface. Priming provides a new surface for the sealcoating to bond. Primers are generally water based coatings, with built in polymers and surfactants that help them to penetrate into the polished aggregates to create the adhesive surface for the sealcoating. Priming is a very cost-effective method to ensure adhesion and they are safe to handle and easy to apply.

CONCLUSION
For proper adhesion it is essential that the asphalt surface be dry, clean, free of contaminants, and have adequate surface profile. The premature sealer failure has been observed to be essentially adhesion failure of the sealer from the top of the “Polished Aggregate”. Such aggregates are created either by the nature of the aggregate or traffic volume. In either case the aggregate surface is too smooth to bond. The surface of such aggregates has to be rendered rough or suitable for bonding through priming. Priming provides a highly cost-effective solution to the premature sealer failure problem.

The term sand roll out generally describes all situations where sand/ aggregate does not stay in uniform suspension, especially during the application or in cured films.  They may appear as unsightly streaks or as free sand released from the cured coating.
Sand roll out may be caused by the deficiencies in the sealcoating mix, the application conditions or a combination of both. Let us consider two broad categories.

Mix design deficiencies:
The mix may be too thin to support the sand suspension, resulting into streaky appearance of the cured film.
Excessive amount of water in the mix will produce thinner dry film that will be too thin to hold the sand and keep them properly anchored in the cured film. Under such conditions,  sand particles will be sticking out of the cured film of the sealer and liable to be knocked off by traffic. It results into pre-mature wear of the sealer.
The sand aggregate quantity may be too high to be suspended by the mix. It results into bunching of the sand during application and an uneven appearance after full cure. These deficiencies will be will be aggravated by thin viscosity of the sealer.
Sand/Aggregate may be too coarse. The average fineness of the sand/aggregate is recommended to be within 50-70 mesh AFS. Too large sand particles will be sticking out of the cured film of the sealer and are very liable to be knocked off by traffic. It results into pre-mature wear of the sealer.
Remedy:
  •  Use the mix design recommendations from your manufacturer.
  •  Avoid excessive amounts of water.
  •  Apply at the recommended coverage rates.
  •  Understand the components of the various terms (ratios, dilution rates, etc.) in the mix design.

Ambient and cure conditions.
Under hot (over 100 º F) pavement and ambient conditions, the water may flash off the sealer film too fast to allow the film to coalesce properly. In visual terms it means egg on a frying pan.
The water evaporates instantly, immobilizing the film.  It results into; 
  •  Poor film formation. The film firmed under such conditions is full of voids and has poor resistance to the elements of destruction.
Sand release from the cured film due to the lack of opportunity for sand particles to interlock and reinforce the cured film. The way sand particles work in the sealcoating is that during the initial drying process they (sand particles) move around in the wet film and interlock. By interlocking they strengthen the film.  If the film dries too quickly they do not get this opportunity to interlock and are liable to be released.
Remedy:  
  •  Fogging the pavement (without puddling) is the preferred method to cool down the pavement.
  •  If fogging is not possible add an additional 3-5% of water to the mix. The amount of water shall always be calculated on the amount of sealer in the tank. For example if you have 100 gallons of sealer, 25 gallons of water and 200 lbs. of sand in your tank,
  •  3-5 % additional water will mean adding 3-5 gallons of water.

Majority sealcoatings are water-based coatings, based on refined coal tar or asphalt cement (AC). Such coatings are safe to handle, store, and provide years of projection to asphalt surfaces, when applied properly and allowed to cure under the right ambient conditions. In this article we will discuss the film formation mechanism and the desired ambient conditions for initial and final cure of sealcoatings.
Water is the major component of sealcoatings, e.g. the sealer supplied as a concentrate contains typically 60% water by volume. After adding 30% water to 100 gallons of the concentrated sealer, the water proportion increases to nearly 70%, by volume. Sealcoatings, like other water-based coatings, cure by releasing water to the atmosphere and reach their full strength after the release of all the water. It will be beneficial to understand how the water is released from the film and the influence of the pavement and ambient conditions on the release of water and cure of the sealcoating films.
Sealcoating professionals are well versed in these details and all make possible efforts to comply, recognizing that deviations may result in poor performance and premature failure.  Even the very best of the coatings if applied and cured improperly is liable to fail.

For the optimum performance, sealcoatings should be;
Mixed accurately per the mix design as agreed for the project i.e.  proper dilution with water, sand loading, additive content, etc.
Applied at the proper coverage rate, (expressed either in gallons/sq. yard or sq.ft./gallon), on a properly cleaned and repaired surface
Allowed to cure “thoroughly” or “sufficiently” under a set of pavement and ambient weather conditions that will allow the coating to attain its optimal firmness.  These “ideal” conditions are simply the ambient and pavement conditions that are specified by the manufacturers and accepted by the industry under which the sealcoatings shall be applied and allowed to cure.

Some Sealcoating Basics
Sealcoating, based on either asphalt or refined coal tar, is stable dispersions of various ingredients in water.  The major ingredients are:
Binder.  The refined coal tar or asphalt cement (AC) is called the binder in sealcoatings. As you may know, both asphalt and coal tar are thermoplastic materials, meaning that they soften and melt at higher temperatures (about 100°F to 180°F) and become hard and brittle to cooler temperatures (below 60°).
The binder is the backbone of sealcoating. It is the ingredient that protects the asphalt pavement. In the wet state (uncured), sealer contains a fine dispersion of binder particles in the range of 2 to 5 microns (human hair is approx. 25 microns or 1 mil), in either spherical or elongated cigar shapes.  Upon full cure the binder forms the continuous film, tightly holding all the fillers and sand/aggregate.
Clay, fillers and aggregates.  To impart proper toughness to the sealcoating film and counteract the tackiness of the binder at elevated surface temperatures.
Specialty chemicals.  Such as surfactants and emulsifiers to stabilize the sealcoating systems.
Water.  As the medium.  In most sealcoatings, water constitutes the major component, more than 60% by volume.

The Film Formation Mechanism
Sealcoatings, like all water-based coatings, attain full cure through the loss of all the water from the wet film.  As the water leaves, the volume of the wet film shrinks.  The shrinkage in volume is directly proportional to the amount of water (by volume) in the mix.  For example, if the mix design has 70% water by volume, the wet film will shrink by 70%, or down to the 30% of the original volume.
The evaporation of water from the wet film produces a steady turbulence in the film and forces the suspended particles into a closer proximity.  The film becomes progressively denser, thus forcing the binder particles to touch one another and fuse into a continuous film, encapsulating the filler particles in the process.  Simultaneously, the excess binder in the matrix allows the film to effectively bond to the pavement surface. 
Descriptions such as the full cure, final set or optimum strength convey the message that sealcoating has reached its full strength and is capable of performing its task, as a protection coating. Properly cured sealcoating form a continuous film, free of voids or imperfections, which stop water, chemicals, salts, etc. from penetrating and damaging the asphalt pavement underneath.  Understandably, any deficiency in the curing process will not allow the binder to fuse properly and leave voids in the film, thus resulting in inferior performance or failure.
During the curing process, all water-based coatings, including sealcoatings, pass through various stages of water evaporation from the applied film.  First it attains initial drying when the film becomes “tack free” to the light touch, then it becomes firmer (about 90% cured) to take light pedestrian traffic, and finally full firmness to withstand light vehicular traffic, when all the water (99%) is lost through evaporation.
The wet sealcoating film is not one solid film but a composite of several layers of very thin films (imagine a sheet of plywood). Like most water-based coatings, sealcoating dries, in successive layers, from top to bottom. As each layer dries, it shrinks in volume, becomes tight and relatively impervious to water vapor, therefore, impeding the evaporation of water from the bottom layers.
The first 80% to 85% of the film dries relatively fast, but the release of the last 10% to 15% of water becomes difficult and requires the right set of ambient and pavement conditions. It’s a fact that the release of water from the bottom layers of most water-based coatings becomes progressively difficult as the film cures.  For optimum performance, all water must leave the film: 80% to 90% is not good enough.  The uncured 10% to 15% of the coating will be torn or dislodged if traffic is allowed on it too soon. The percentages are mentioned here only to explain the phenomenon.  They will, of course, vary with material and mix designs, e.g. mix designs with fillers and/or aggregates will dry faster than sealcoatings coatings without them. 

The Cure Conditions
The conditions described below play the decisive role in determining the thoroughness of the overall cure process, therefore, sealcoating performance. These conditions are the recommendations of the industry and its research association, Pavement Coatings Technology Center (PCTC), University of Nevada at Reno.  These factors are important in obtaining the optimum cure of sealcoatings.
1. Temperatures: Both Ambient and Pavement
Sealer should not be applied unless the pavement temperature is at least 50°F and the air temperature is 50°F and rising.  As described in the foregoing sections, the fusion of the binder particles (in the sealcoating) to form a uniform and continuous film depends on their ability to soften under the ambient and pavement temperatures. The process of fusion is greatly enhanced at higher temperatures; say 75°F to 85°F.  Conversely it is significantly reduced at temperatures below 50°F.  Let us review the extremes; cold and hot temperature applications.
Cold application and cure conditions
When sealcoating is applied below 50°F, tar (or asphalt particles do not soften and form a continuous film, thus leaving clay and filler particles uncoated. The color of the sealcoating cured under such conditions usually turns out grey and blotchy in appearance and never returns to its normal slate black appearance even at higher pavement temperatures, at a later date, because the temperature of the pavement normally does not reach high enough to re-melt the binder particles and force them to flow and form a continuous film.  Even if the pavement temperatures reach high enough, still it will not assure proper fusion.  The binder particles will melt but will not have the capability to flow and envelope the clay and filler particles already set in a rigid matrix.  Needless to say sealcoating cured under cold weather conditions lack the integrity and sealcoating properties that are normally expected.
Hot applications and cure conditions
Sealcoating applications under hot temperatures can be equally problematic.  Sealcoatings should not be applied under the summer sun (90°F ambient) without first cooling the surface with a find mist of water, also called “fogging”.  Water should only dampen the pavement, without leaving puddles.
If applied to a hot pavement without “fogging” it, the sealcoating film almost gets “baked” as soon as it hits the pavement.  The sudden loss of fluidity of the film, due to flashing of  water, immobilizes binder particles and prevents them from fusing and forming a continuous film. Devoid of proper fusion process, binder particles do not effectively envelop the clay and filler particles in the sealer film.  Additionally, binder particles under such conditions do not reach the hardness imparted by the clay and fillers and continue to stay sticky and soft.  And that could lead to lead to a problem called “tracking”, where the sealer is tracked on the floors or carpets, etc.
2. Humidity or Relative Humidity (R.H.)
Humidity or Relative Humidity (R.H.) of the atmosphere plays a significant role in the cure mechanism.  It directly influences the rate of water loss from the sealcoating film.
Relative humidity (R.H.) is the ratio of the actual moisture content of the air, at a specified temperature,  to its total capacity.  For example, 50% R.H. means that only half of the air’s total capacity to hold water has been used and it is capable of absorbing another 50% of moisture or vapor from the surroundings.
Conversely, 90% means that it has very little capacity left (only 10%) to absorb additional moisture, thus drastically slowing down the release of water. from the sealcoating film. The sealer film will release only that much amount of water that can be accommodated by the atmosphere.  The atmosphere and the surrounding environment can be thought of as a sheet of paper towel:  when dry it will soak up the spill but will not mop up if the towel is too wet.
Sealcoatings, understandably, will cure faster at lower humidity than at higher humidity.  Under highly humid conditions, sealcoatings shall be allowed longer drying time before the application of the subsequent coats and finally opening to traffic.
3. Wind Velocity
The drying and cure times specifications do not take wind velocity or air movement under  consideration, however, it is a known fact that air movement, especially under highly humid conditions, helps sealer dry faster than without any air movement.  A light breeze assists in the  dissipation of the water and volatiles from the immediate vicinity. Conversely, under low humidity conditions (below 20-25%), the air movement may cause the sealcoat to dry a bit too fast.

Questions that are commonly asked by sealcoating professionals are how to adjust mix design for weather related conditions or sand/aggregate loadings or simply in the amount of water in the mix. Before we answer such questions, it is imperative to understand some fundamentals that relate to film formation, mechanism and the factors which influence the proper set and final cure of sealer films. Lets us start with the basics; sealer composition, film formation, the conditions for proper film formation and finally the adjustment of mix designs.

Some Sealcoating Basics - Majority sealcoatings are intimate dispersions of refined coal tar (or asphalt cement- AC), clay, emulsifiers and specialty chemicals in water. Being water- based, sealcoatings are safe to handle and store. Over the decades it has been established that sealcoatings provide years of protection to asphalt surfaces, when applied properly and allowed to cure under the right ambient conditions.
Mix Designs - Sealcoatings are usually supplied in a concentrated form, which have to be mixed with water, sand/aggregate, and additives (optional), prior to application.
Water - (a) gives fluidity to the sealer, (b) satisfies the water demand of sand. All fillers absorb water which is called their water demand which has to be satisfied by water in the mix. Fillers also absorb the binder which is called the binder demand. (c) Water also wet out the pavement for proper flow, leveling and adhesion of the sealer to he pavement.
Sand /Aggregate - (a) imparts slip resistance and traction (b) uniform textured, non-streaky appearance with reduced sun glare (c) improves wear ability and (d) hides minor surface defects.
Additives - are added to enhance the performance or speed up drying or sand suspension or all of the above. There are many additives that are recommended to perform specific function in sealer mix designs.  
Mix designs are simply the guideline for the proportions in which these components are to be mixed, according to the usage requirements of the pavement. For example, low traffic may require, low water of dilution, low sand loading, one coat application. Conversely, medium traffic may require more water, more sand and the use of an additive. Mix designs are also adjusted to accommodate weather conditions and or varying amounts of fillers, additives, etc.   

The Cure & Film Formation Mechanism
Water is the major component of sealcoatings. The sealer supplied as a concentrate, typically contains 60% water by volume. After adding 30% water to 100 gallons of the concentrated sealer, the water proportion increases to nearly 70%, by volume.
Sealcoatings, being water-based, attain full cure through the loss of all the water from the wet film.  As the water leaves, the volume of the wet film shrinks, in proportion to the amount of water (by volume) in the mix.  For example, if the mix design has 70% water by volume, the wet film will shrink by 70%, or down to 30% of the original volume.
As the water evaporates, it creates a steady turbulence in the sealer film, which forces the suspended particles (binder, filler) into a closer proximity.  The film becomes progressively denser, thus forcing the binder particles to touch each other and fuse into a continuous film, encapsulating the filler particles, in the process.  Simultaneously, the binder bonds to the pavement.
Properly cured sealcoatings form a continuous film, free of voids or imperfections, which stop water, chemicals, salts, etc. from penetrating and damaging the asphalt pavement underneath.  Understandably, any deficiency in the curing process will not allow the binder to fuse properly and leave voids in the film, thus resulting in inferior performance or failure.

A closer look at the sealer film
The wet sealcoating film is not one solid film, but a composite of several layers of very thin films (imagine a sheet of plywood). Like most water-based coatings, sealcoating dries, in successive layers, from top to bottom. As each layer dries, it shrinks in volume, becomes tight and relatively impervious to water vapor, therefore, impeding the evaporation of water from the bottom layers.
The first 80% to 85% of the film dries relatively fast, but the release of the last 10% to 15% of water becomes difficult and requires the right set of ambient and pavement conditions. It’s a fact that the release of water from the bottom layers of most water-based coatings becomes progressively difficult as the film cures.  For optimum performance, all water must leave the film: 80% to 90% is not good enough.  The uncured 10% to 15% of the coating will be torn or dislodged if traffic is allowed on it too soon. The percentages are mentioned here only to explain the phenomenon.  They will, of course, vary with material and mix designs, e.g. mix designs with fillers and/or aggregates will dry faster than sealcoatings coatings without them. 

The Cure Conditions
Pavement and ambient temperature, Relative Humidity and wind velocity have a very profound effect on the rate of water release from wet sealer film and the final cure.

1. Temperature - both ambient and pavement, influences both aspects in the proper film formation and final cure; release of water and fusion of binder particles.

Cold Temperatures: The minimum recommended application temperature for a sealer is 50°F, and rising.  The fusion of the binder particles to form a continuous film is greatly enhanced at higher temperatures. Conversely it is significantly reduced at temperatures below 50°F. 
When sealcoating is applied below 50°F, tar (or asphalt particles do not soften and form a continuous film, thus leaving clay and filler particles uncoated. The color of the sealer, cured under such conditions, usually turns out grey and blotchy in appearance and never returns to its normal slate black appearance even at higher pavement temperatures, at a later date, because the temperature of the pavement normally does not reach high enough to re-melt the binder particles and force them to flow and form a continuous film.  Even if the pavement temperature reached high enough, still it will not assure proper fusion.  The binder particles will melt but will not have the capability to flow and envelope the clay and filler particles already set in a rigid matrix.  Needless to say sealcoating cured under cold weather conditions lacks the film integrity and the expected performance properties.
Mix Design Alteration Suggestion -
(a) Consider using an additive (1-2% on sealer volume) that will help the sealer dry faster. Such additives contain fast evaporating solvents which combine with water in the sealer, accelerating the evaporation rate, at low temperatures.  Most rubberizing (performance boosting) type additives also speed up the water evaporation.  Such additives form a polymer network within the sealer film, which forces the water out of the film at a uniform rate.
(b) Reduce water of dilution as much as possible, use the lower limit.

Hot Temperatures:  Sealcoating applications under hot temperatures can be equally problematic.  Sealcoatings should not be applied under the summer sun (90°F ambient) without first cooling the surface. If applied to a hot pavement, the sealcoating film almost gets “baked” as soon as it hits the pavement, resulting in a film full of pinholes.   
The sudden loss of water immobilizes binder particles in the sealer and prevents them from fusing into each other and forming a continuous film. Devoid of proper fusion process, binder particles do not effectively envelop the clay and filler particles in the sealer film.  As a result, binder stays as discrete particles, not hardened by clay and filler particles. The sealer film, under such cure condition, may not reach the hardness and continue to stay sticky and soft.  And that could lead to lead to a “tracking” problem, where the sealer  may be tracked into the buildings onto the carpet or tiles.
Mix Design Alteration Suggestion - 
(a) Cool the pavement with a find mist of water (“fogging”). Avoid puddling, otherwise sealer may just slide right off during application.
(b) Not as effective as fogging but acceptable and generally used approach is to add more water in the mix  (3-5%), to increase fluidity.

2.  Relative Humidity (R.H.) - Relative humidity (R.H.) or humidity is another major factor that greatly influences the film formation and final cure of the sealer.  R.H. is the ratio of the actual moisture content of the air, at a specified temperature, to its total capacity.  For example, 50% R.H. means that only half of the air’s total capacity is used and it is capable of absorbing another 50% of moisture or vapor from surroundings.  Conversely, at 90% R.H., it has very little capacity left (only 10%) to absorb additional moisture, thus drastically slowing down the release of water (cure) from the sealcoating film. The sealer film will release only the amount of water that can be accommodated by the atmosphere.  The atmosphere and the surrounding environment can be thought of as a sheet of paper towel:  when dry it will soak up the spill but will not if the towel is too wet. At 100%R.H., the sealer film may take if not days, several hours to cure.
The slow cure is further aggravated by low temperatures, e.g. the rate of water evaporation is nearly halved for a 10 degree Celsius drop in temperature, at a given R.H.
Mix Design Alteration Suggestion - Reduce water in the mix design, use only as much as needed for a good workable consistency.
Allow longer drying time in between coats; do not apply the next coat even if the previous coat “looks” firm.

3.  Wind Velocity - Wind velocity or air movement, especially under highly humid conditions, helps sealer dry faster than without any air movement.  A light breeze assists in the dissipation of water and volatiles from the immediate vicinity. On the other hand sealer may dry too fast for properly handling windrows, under breezy conditions at low humidity ( 20-25%).
Mix Design Alteration Suggestion - May consider adding a bit more water if the sealer is drying too fast for proper flow and leveling of the wet sealer.

Some other Mix design Suggestions.
Water - Within the mix design range recommended by the sealer manufacturer, use only as much water as is needed for proper flow and workability. Excessive water reduces the cured film thickness and may result in pre-mature wear.
Sand/Aggregate - The amount of sand/aggregate may be adjusted according to the pavement usage.
A lower amount may be acceptable for low traffic pavement with a tight profile,
While a higher sand loading may be essential for rough pavement , medium traffic or inclined surfaces.
The sand/aggregate loading shall not exceed 4-5 lbs. per gallon of the concentrated sealer because; being filler, sand will absorb binder as well as water. It is a desired property. By absorbing binder, the sand becomes an integral part of the coating. The limit is about 5 lbs., because above 5 lbs. sand absorbs too much binder to be available for adhesion to the pavement.  The coating becomes too rigid to flex with the pavement. Also it may show adhesion problems.
Another important consideration is the mesh size of the sand/aggregate. It must be within 50-60 mesh size range, because finer the sand, higher the number of particles per lb., higher will be the total surface area and higher binder absorption. Sand with 100 mesh size has 8 times the number of particles and twice the surface area than 50 mesh sand.  The binder and water absorption is directly related to the surface area.
Additives -  Use where they add a definite value or solve a situation. Out of the myriad of additives, it will be prudent to ask your supplier about the specific role of the recommended additive and how will it benefit the overall performance.   Ignore suggestions to use vinegar or Elmer’s glue, or magnesium chloride, etc. as additives. They may damage your sealer. When in doubt, discuss with your materials supplier.

Use the mix design guideline as suggested by your manufacturer and contact them for special situations, where the mix designs are not workable; material preparation, application, pavement or weather conditions.  Work out the details which suit your set of conditions.

Asphalt pavements, like other construction materials, have a service life, which can be extended through proper maintenance by protecting them from the damaging elements of weather, salts, chemicals, petrochemicals, etc.

The purpose of this presentation is to demonstrate the cost benefits, in real dollars, of a properly maintained asphalt surface versus an asphalt pavement which has been minimally maintained.

LIFE-CYCLE COST ANALYSIS  (LCCA)
Life-Cycle Cost Analysis (LCCA) is a process for evaluating the economic worth of a pavement segment by analyzing initial costs and discounted future costs such as preventive maintenance, resurfacing, rehabilitation and reconstruction cost, over a defined analysis period. LCCA is only a tool in decision making process, it does not dictate the decision.
All alternatives are to be included in the LCCA. For example, complete replacement is generally the most expensive alternative but it should not be disregarded simply because of the expectations of the high cost. The analysis may show replacement as the highest cost but the cost difference between replacement and the other alternatives may be small  enough to make the replacement a better choice.

LIFE EXPECTANCY OF ASPHALT PAVEMENTS
The general consensus of the industry regarding the life expectancy of an asphalt pavement is approx. 7-8 years without any maintenance. Home driveways may last 10-15 years, without maintenance.
The life of an asphalt pavement depends on the following factors;
  •  Pavement design i.e. base, sub-base, drainage,  asphalt mix, compaction, depth of the asphalt, etc.
  •  The traffic bearing capacity
  •  Traffic frequency
  •  Exposure to damaging elements, e.g. de-icing salts, oil, grease, gasoline, fats, etc.
  •  Maintenance e.g. sealcoating, crack filling, patching, etc.
For the sake of understanding, the life of an asphalt pavement is the period during which it will preserve its strength to bear the traffic loads for which it is designed. For example a commercial parking lot will need to be repaved after 7-8 years.

LCCA of a commercial parking lot (10,000 Sq. Yards) is tabulated below, both;
with a regular preventive maintenance program, using  a sealcoating based on refined  tar emulsion.
  •  The sealcoating and other repairs will be done at every 3 years.
  •  The sealcoating is to be done during the first year of the installation. –
  •  The pavement shall be allowed to cure to rid of the surface oils. The time period is minimum 90 days. 
  •  After the first three years, some minimal repair (crack filling) may be required. Cracks may develop due to pavement distress.

Without seal coating, only the damaged areas are repaired as needed. The cost of repairs escalate with each passing year. It has been observed that fine hairline cracks appear during the first year of installation, which widen and multiply with time. Water seeps into the pavement through these cracks and damages the base courses. Generally, a parking lot will require an overlay after seven years.

Your Parking Lot Maintenance Program
A powerful strategy should be the heart of your efforts to maintain the quality of your asphalt parking lot. Your program should be designed to stretch dollars, extend the life of your paved surfaces and simplify the job of the property manager.
Unfortunately much like driving a new car off of the car lot, asphalt begins to deteriorate in a very short period of time. Just like a car requires routine oil changes and tune-ups, your parking lot requires standard maintenance to ensure that it achieves its maximum useful life. Research has shown that proper asphalt maintenance can save property owners tens of thousands of dollars over the life of the pavement.
By taking part in a well planned parking lot maintenance program you are maximizing the life of your asphalt pavement, and ensuring that you are doing your very best to protect your investment.

Initial Details
A well planned pavement maintenance program should allow you to work within your budget to preserve and protect your parking lot investment.
  • Professional evaluations done by an experienced seal coating contractor.
  • Implementation of a detailed maintenance schedule.
  • An evaluation that takes into consideration:
          - Current and future pavement conditions.
          - Maintenance and repair options.
          - Budgetary concerns.
          - Any other factors that assist in developing an effective maintenance and repair plan.
Individual maintenance options such as Asphalt Repairs, Sealcoating, Crack Sealing, and Line Striping all should be considered in your maintenance plan. Of these elements; Sealcoating is essentially the most important, slowing the inevitable degradation of the asphalt pavement will make the biggest difference in the long term success of your plan.
As a management tool this program enables you to plan your pavement maintenance so you can maintain your parking lot in the most cost effective way. A parking lot maintenance program should be a long-term approach that ties together all of the various maintenance options under one program so you will be able to get the most out of your pavement surfaces - one of the largest investments on your property.

Why Should I Sealcoat My Parking Lot?
A common question asked by property owners and managers. The answer is twofold:
To protect the pavement from accelerated deterioration. There is no question that your parking lot takes a beating day-in and day-out. Daily traffic, gasoline and oil leaks, rain, and freeze/thaw cycles all break down the chemical bonds in the asphalt. The sun has an especially harmful effect on the asphalt, its ultraviolet rays rapidly increase the rate of oxidation, causing the pavement to become dry and brittle. Sealer is designed to dramatically reduce the affect of those factors on the asphalt pavement. When correctly mixed and applied, the sealer acts as a barrier, preventing damaging elements from reaching the asphalt. A high quality sealer should be applied every 2 to 4 years depending on the type and frequency of traffic.
To enhance the curb appeal of the property. The saying “You never get a second chance to make a first impression” is never more true than in real estate. The curb appeal of your property has a huge affect on the clientele and/or tenants that frequent your business. Just as a fresh coat of paint on an old building can offer new perspective, so can a freshly sealed parking lot. It tells your existing and potential customers that you care about the details.
Our company leads in the local industry and are well known as experts in this area. We take pride in delivering a hassle-free sealcoating and pavement maintenance process to our customers. We strive to get the job done in a manner that is least disruptive to your business. We can arrange for the work to be completed around your schedule. Nights, weekends, and even holidays, we will do whatever it takes to get the job done with as little impact on your business as possible.

Crack Sealing
A very important step in any pavement maintenance program. Cracks result from various factors including freeze/thaw cycles, differential settlement, chemical spills, etc... Once cracks form they allow water into the foundation of your parking lot. Many foundations are made of limestone which washes away easily when introduced to water. Once the foundation erodes away, the pavement loses the support it needs to perform properly. This results in dips, “alligator” cracking and eventually potholes.
With a proactive approach, and the help of an expert, you can prevent extensive damage. Crack sealing is designed to keep water out of the base layers of the asphalt where it is likely to cause the most damage.

A Comprehensive System Works With Your Customer!
#1 Assessment
The first step is to conduct a physical assessment of each parking lot. We note the details of the condition of the pavement including dips, rutting, potholes, all cracks by type, location, and severity, existing patchwork, etc...
#2 Condition Analysis
The condition of each parking lot is analyzed by various methods. During this step a plan is developed to address every problem area on the parking lot. Once this analysis is completed we document each problem area and correlate it with a diagram of your parking lot. Condition Analysis are generally completed annually to monitor the performance of the pavement.
#3 Identify Maintenance Options
Next we rank the problem areas and recommend specific repairs. Rather than rank the problem areas from worst to best, we rank them from most important repair to least important. Sometimes it’s more important to prevent an area from getting worse than to repair an already deteriorated area.
#4 Implementation
With the assessment and condition analysis in hand it is time to sit down with you and determine the best course of action for your parking lot. When the time comes to execute the plan, we get the work done in a manner that is least disruptive to your business.

Parking Lot Marking
Many property owners and managers will use parking lot marking for a quick, eye-catching and affordable way to invigorate the appearance of their properties. Properly laid-out and painted parking lots will create a sense of safety and organization for vehicle and pedestrian traffic. Whether you’re restriping due to recent sealcoating or paving work, to meet ADA guidelines, or just to give the property a fresh new look, our experts will complete the job with quality and efficiency at a reasonable price.
There are several options available when it comes to parking lot marking layouts and styles. Whether it’s single line, double line, straight or round end design we can help with the design of your lot or follow a set of well drawn blueprints. We also do playgrounds, basketball and tennis courts, running tracks and athletic fields. If you have a pavement marking need, we can service it for you.

There are some things you should know about your new asphalt pavement, and how soon you can successfully apply a sealcoating to that newly laid surface. Please take a moment to understand what to expect, and some DO’s and DON’Ts for freshly installed asphalt surfaces:
•    How long should wait before I can apply a sealcoating to my new asphalt?
Newly installed asphalt pavements must be allowed to cure sufficiently so as to allow the oils in the new asphalt to oxidize and dissipate. In most cases we recommend at least 90 days in warmer weather to allow this process to take place. These oils in the new asphalt can cause a sealcoating to dis-bond from the asphalt surface if they are not given time to cure out.
•    How can I know that the oils in asphalt have dissipated enough so as not to cause a problem?
A simple way to check for oils on a recently installed asphalt pavement is to perform a “Water Break Free Test”. This test will help to confirm that the surface oils have dissipated, by observing how a gallon of clean water casts out across the pavement surface. The water should sheet out and uniformly wet the surface with out beading or showing oil rings.
•    Is there any way to speed up the process so I can apply a sealcoating sooner?
Only time can properly cure out a freshly laid asphalt surface. It is not recommended to apply a sealcoating while significant oils are still present on the surface. There are several primers that work well on smaller patched areas and can act as adhesion promoters between the newly installed patch and the sealcoating that will be applied to this surface.

It is recommended that you consult with your sealcoating contractor for advise on this subject and allow them the opportunity to help you make an educated decision on what will work the best for your situation.

A proper sealcoating and crack sealing maintenance program will not only keep your asphalt pavement looking beautiful, it will also save you money by protecting the asphalt from deterioration. Please take a moment to understand what to expect, and some DO’s and DON’Ts for freshly sealcoated asphalt surfaces:
•    How long should I stay off of my driveway?
As the manufacturer we recommend 24-48hrs. You will be able to walk on your driveway much sooner than this, but we recommend not driving on it for at least 36hrs if at all possible.
•    How long does it take a newly sealcoated driveway to dry?
In ideal weather conditions the drying will only take a few hours. However, just because it’s dry on top and dry to walk on does not mean it’s CURED. Curing is the evaporation of all liquid from the sealer. The dryer and hotter the weather the faster it will cure.
•    Can I drive on a driveway that is NOT fully cured?
Absolutely, you can drive on your driveway. 100% cure may take longer, but after 36 hours it will be cured to about 95% and you will not hurt your sealcoat. That last 5% of the cure takes the longest.
•    I’ve noticed that I’m leaving tire marks on my new pavement, is there something wrong?
Nothing is wrong!  This is a normal part of the process.  The material used to seal your driveway is thermoplastic and the marks left by your tires will run themselves out and disappear. It’s just like freshly paved asphalt, those tire marks will disappear. Once your driveway has achieved a complete 100% cure, it will no longer mark.
•    Is there anything I can do to avoid marking the driveway before it is 100% cured?
Yes. Try to avoid turning your tires very hard or turning the wheels while the vehicle is not moving. Again, if you do leave marks, they will eventually go away.