How to alter mix designs according to cure conditions
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 has 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 for 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 the pavement.
Sand/Aggregate – (a) imparts slip resistance and traction (b) uniform textured, non-streaky appearance with reduced sun glare (c) improves wearability 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 a 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 (i.e. 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 the 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 which 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 fine mist of water (“fogging”). Avoid puddling, otherwise, the 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 (i.e. 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, the 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.
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 premature 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 a filler, the 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 which 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 are 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 material 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.
Basic Talking Points for Sealcoating Professionals on The Benefits of Sealcoating Asphalt Surfaces
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 the 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
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. Yds.) 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 a minimum of 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 will escalate with each passing year. It has been observed that fine hairline cracks appear during the first year of installation, which will 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.
A well-planned pavement maintenance program should allow you to work within your budget to preserve and protect your parking lot investment.
Professional evaluations should be performed 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.
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 effect 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 truer than in real estate. The curb appeal of your property has a huge effect on the clientele and/or tenants that frequent your business. Just as a fresh coat of paint on an old building can offer a 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.
A very important step in any pavement maintenance program. Cracks can 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.
Our Comprehensive System Works With You!
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.
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 a 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.
SEALCOATING ONTO NEW ASPHALT
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?
without beading or showing oil rings. 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
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.
CARING FOR NEWLY SEALED ASPHALT
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 24-48 hrs. You will be able to walk on your driveway much sooner than this, but we recommend not driving on it for at least 36 hrs. 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.