Many individuals approach us about asphalt work for their driveways and parking lots for their small business that are unfamiliar with the nature of the work that we do. We have prepared this brief informational packet to help these potential customers understand the nature of what we do and to provide them with an understanding of what to expect from this work. So let’s begin with a quick overview.

What Are We Even Talking About?

Thinking About Asphalt…

From the outside looking in, installing asphalt pavement seems like nothing more than pouring a liquid out of a truck, letting it dry and the job is done. However, the installation of hot mix asphalt is nothing at all like that, and the process is not as simple as a layman may think.

The key to any asphalt paving job requires a well-compacted stone base course prior to the hot mix asphalt installation. There are several options for the materials used to create that base; limerock, dense-graded aggregate base, soil cement, shell rock, reclaimed asphalt pavement, and 12.5 mm type B asphalt can all be used to create this base course.

²⁴ “Therefore everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock. ²⁵ The rain came down, the streams rose, and the winds blew and beat against that house; yet it did not fall, because it had its foundation on the rock. ²⁶ But everyone who hears these words of mine and does not put them into practice is like a foolish man who built his house on sand. ²⁷ The rain came down, the streams rose, and the winds blew and beat against that house, and it fell with a great crash.”                                                          Matthew 7:24-27

Did I mention how important a good base is to the success of a paving job?

The thickness of the asphalt required varies from project to project and is based on the expected usage for the paved area, the number of vehicle trips, and the estimated single axle load of the vehicles using the paved area. Axle load is the weight of a vehicle divided up between each axle, or pair of wheels, as it would be while in use. These factors all must be evaluated to determine the required structural strength needed for the paving structure which is the whole of the system. In evaluating this, the thickness of the underlying base layer of rock can be just as important as the thickness of the asphalt paving. In typical use standard duty and heavy-duty asphalt paving may both consist of one and a half inches of asphalt with the rock base thickness being increased to account for the heavier loads expected. Depending on the nature of your project we often recommend between one and a half to two inches of asphalt on driveways and parking lots.

Other factors to consider include the evaluation of slope and resulting runoff. Positive drainage is necessary to ensure the longevity and serviceability of your pavement, while the nearby structures and adjacent properties can be affected by the resulting redirection of rainwater.

Sometimes existing asphalt or other materials must be removed before paving can be placed, but not everyone needs to jackhammer up an existing surface and begin again. Asphalt that is in good condition with minimal cracking, should have the cracks filled and can be sealcoated to preserve it. Asphalt that is well oxidized and severely cracked can be milled, which removes the asphalt surface only. The surface may be completely removed so that the base course can be inspected with additional material being added or repairs made as needed. The surface may also be milled to a level and depth which removes existing cracks. In either case, a fresh asphalt surface course is applied.

The commonly used asphalt mixes for surface courses of asphalt are named for the size of the aggregate used in the mixture, being either a 9.5mm or 12.5mm rock. While the mix contains many sizes of stone these represent the largest in the mixture and the smoothness of the finished product is affected by this. Larger stones may provide a more durable surface but a more glass like finish requires smaller aggregate and fine materials to make up the asphalt mix that is laid.

Let’s talk about how to prepare and care for your pavement.

Care and Feeding of your New Asphalt

Properly laid, cured, and maintained asphalt pavement can keep it’s looks and strength and provide 20 to 30 years of reliable service. Neglected, the surface can begin to deteriorate almost immediately, possibly failing in as little as 5 years. Asphalt is a reliable paving material providing the best value for your dollar of all the materials on the market. Make sure that it remains attractive and functional for many years by taking some basic steps to care for it and providing for some regular maintenance.

While you can start driving on asphalt as soon as it is dry, it will not reach maximum strength and resistance to damage until it is fully cured. This process of curing can take up to a year. That makes the first year the most critical time if you want to get the longest service life out of your investment. Here are a few steps to take before we begin and some guidelines to follow for the first year afterwards:

• Encourage drivers to slow down and drive sensibly to avoid scuffing or scarring the asphalt. Donuts, spinning wheels, and cutting the steering wheels back and forth while not moving are all bad for the new surface. Any action that can subject the asphalt surface to high twisting or shearing forces runs the risk of opening the surface and making it vulnerable to further damage. Turn the wheel only while moving until the asphalt hardens.
• Be aware of the time vehicles remain parked in one location without moving, especially when temperatures are high and the pavement is soft. Asphalt pavement contains air voids that provide some of its strength. Prolonged exposure to continuous weight in one location can continue to compact the asphalt removing these air voids and creating depressions where the weight is concentrated.
• Consider restricting the weight of vehicles being driven on it when it’s new as large heavy vehicles can cause surface scarring and create ruts in the asphalt surface while it is still soft. Large vehicles also expose the asphalt to higher stresses when a wheel is turned as it concentrates more weight and stress in a small area possibly damaging the asphalt surface.
• Oil and fuel spills break down the chemicals that bind asphalt together and can do so very quickly. Clean them up quickly by using either sawdust or cat litter to remove as much as possible. Hose the area down and clean with a commercial degreaser of tri-sodium phosphate. Avoid using solvent based chemicals.
• Don’t let grass and weeds creep up on your pavement. Roots and weeds create bumps and cracks that grow into holes. Grass that moves up to the edge of your pavement can obstruct water flow and create areas where water pools and causes damage to not just the surface but to the base beneath as well.
• Seams and Joints are from different passes with our paver and hand worked areas. Vehicle traffic will help make these disappear over time.
• Areas where sand has been spread on a newly paved surface is not an indication of anything wrong. Rather it is an attempt to help minimize scarring and has been placed to help seal the asphalt. This will dissipate over time.
• Loose rocks are surface aggregates that will usually cease to appear after 30 days of traffic on the asphalt. This is entirely normal and should be expected.
• Barricades are sometimes left in place at the end of the day, especially when multiple days of work is required to complete a job. Do not move these barricades and drive on the surface. Not allowing the proper cure time will void the warranty.
• In parking lots and areas where there may be vehicles out of your control it should be expected that these must be removed. Cars in the work area will be towed at the owner’s expense. We recommend placing a tow truck on call for the day we begin work.

Once the asphalt is fully cured (NOT BEFORE!) consider applying a quality sealcoating to provide a moisture barrier and prevent fading. This extends the functional life of your asphalt parking lot. Depending on the level of traffic in your parking lot consider having sealcoat professionally applied every 3-5 years to keep it at its best.

Sealcoating an asphalt pavement involves the application of a bituminous liquid formula to the surface course of asphalt. Once cured this coating protects the asphalt surface from the erosion of fines, which exposes a rough stone surface, helping keep the pavement smooth. Properly applied seal coatings fill small hairline cracks up to ⅛” and can extend the life of an asphalt parking lot by up to 20 years. Over application can result in peeling and does not benefit the life of the asphalt. The benefits of maintaining this smooth surface include protecting the parking lot from gas & oil spillage, oxidation of the upper layers by the sun, deterioration from contact with many common chemicals (this includes de-icing agents and detergents), and the oil-based formula also repels water and prevents the formation of standing puddles; these can lead to alligator cracking and the penetration of water into the base material below.

Inspect your pavement regularly. Patch holes and apply crack sealant immediately when damage is detected to prevent these areas from growing. A little routine maintenance can keep problem areas from growing beyond the point where you can fix them yourself, so spot check your lot regularly.

Preparing and caring for Sealcoating

• Please turn off sprinkler systems the day before sealcoating is scheduled to begin. Moisture interferes with the adhesion of asphalt materials and should be eliminated to every possible extent.
• Please allow for proper curing of the sealcoating.
  • Surface Set – 2 hours of drying should be enough to prevent rain from affecting the coating.
  • Minimum Cure – 12 hours of curing are required before paint can be applied to new surface.
  •  Cure – 24 hours are required before the surface cures to the point that it can be opened to traffic.
• The appearance of scuffing, tire marks, and discoloration are normal on a freshly coated surface. These marks and discoloration should begin to blend in and fade over a period of 30 to 60 days.  
• Sealcoat does not fill in cracks, its purpose is to protect the underlying material from damage caused by moisture penetration and to slow the loss of oils from the asphalt surface that leads to the breakdown and loss of fines from the pavement.
• The application of a sealcoat treatment can reduce the required maintenance and extend the service life of a paved asphalt surface by 3 to 5 years.

What is Crack Sealing

• Crack seal application requires a clean surface to bond with. This is achieved by manual brushing of the crack and through the use of compressed air. This can cause fine dust and particles to become airborne, which can cause difficulty breathing. Please stay upwind during this work and away from workers when compressed air is in use.
• A sealed surface should be kept free of traffic until it has properly cured for the best results. The amount of time required varies depending on the characteristics of the sealant used, the weather conditions when applied, and the expected traffic volume the surface will carry.
• Application of sealant into cracks in the asphalt surface course should completely fill the crack in order to prevent moisture penetrating through the layer and causing the deterioration of the base material underneath.
• 75% of unsealed cracks in asphalt develop into potholes within three years of first appearing. Less than 1% of sealed cracks develop into potholes within that same period.
• Properly sealing cracks in asphalt when they appear can extend the service life of a paved surface by 3 to 5 years while simplifying future repairs by protecting and preserving the base material underneath.    

Paving’s Problem Child

Reflective Cracking

Reflective cracks occur where there are existing breaks or cracks in underlying layers. Stresses from the movement of these layers caused by shifting loads or thermal expansion cause the concentration of stresses and a crack propagates through the overlay and is reflected in the surface over time.

Common sources of reflective cracks include joints and cracks in concrete pavements, low-temperature or shrinkage cracks in asphalt pavements, longitudinal joint failures, and fatigue cracks. Reflective cracks can also form due to sub-grade shrinkage and from subsidence over culverts or other utilities.

Reflective cracks are generally not related to an applied load but loading does accelerate the rate and severity of deterioration. These cracks are a problem because they allow water into the pavement which weakens the pavement structure and contributes to premature deterioration of the overlay, usually showing up as a loss of material at the crack, bumpy ride, or other evident signs of deterioration.

The prevention of reflective cracking is nearly impossible when laying an asphalt pavement over a base in which these faults are already present. These areas will eventually exhibit signs of cracking, mirroring the cracks in the surface underneath. Most of the methods used when overlaying areas exhibiting these signs of failure are designed to mitigate the severity and the number of cracks that will reappear in new asphalt surface. Some of the ways to address the problem include:

• Utilizing mixes with higher cracking resistance. These typically include a modified asphalt binder and may include a gap-graded aggregate structure.
• Constructing thicker overlays. Thicker overlays allow the stresses to dissipate and may reduce the crack width or severity.
• Placing a crack-relief mechanism. These include unbound relief layers, interlayers, geo-synthetic fabrics, and highly specialized asphalt mixtures These techniques can impede the reflection of cracks by minimizing the tension transferred to the overlay.
• Recycling in-place. Some or all of the existing asphalt is reworked to remove the old crack.
• Using saw, cut and seal. In this process, the crack location and depth is identified and a saw-cut is made, to form a clean opening which can be sealed to minimize damage.  
• Applying one of the fractured slab processes for overlays on concrete. Rubblization and break-and-seat are effective techniques for reducing and possibly eliminating reflective cracking on old concrete pavements.

All attempts to reduce reflective cracking are differing methods of diffusing the areas where stress concentrates throughout a larger area. This hopefully prevents the pavement from failing along the original crack and reappearing in the new surface. The only way to guarantee the elimination of these kinds of failures in an asphalt pavement surface involves the complete removal of the original surface to allow the examination and rehabilitation of the underlying layers prior to laying a fresh course of asphalt. For overlays showing early signs of reflective cracking, the typical repair strategy to prolong pavement life is to perform crack sealing to prevent moisture from entering and thereby degrading the asphalt and underlying base material.

While these types of cracking can appear when using asphalt, a flexible pavement, on top of any material, we most often see this type of failure when a concrete surface, laid without proper sub-grade preparation, begins to fail and is then overlaid with asphalt at a later date.

In closing…

I’ve prepared this document hoping that you might find some of the information contained in it useful in your research into the handling of your project. If nothing else, I hope this allows you a greater understanding of the various terms that may come up as you request quotes from contractors, and no matter who you choose I hope this helps you to better understand your options and exactly what it is that you are paying to have done.

Sincerely,

on behalf of Kudzue 3 and Black Jack Asphalt,