Asphalt Paving and Sealcoat  Blog

COMMON ASPHALT PROBLEMS part1

Cracking Repairable with Sealant or Fill

Asphalt cracks that form in the pavement surface can allow many harmful substances - including water, salts and engine oils - into the base and subgrade, effectively leading to the failure of the pavement surface. There are many types of asphalt cracking and many causes for these differing problems. In many cases, cracks develop because of the expansion or contraction of the base or subgrade or because of voids that form between the layers or courses of pavement. These cracks can form randomly or in the following specific forms. In all cases, if repaired while still within ¼" to ½", these cracks are easily repaired and maintained.

Transverse cracking

Transverse cracking, or cracks that occur across the pavement surface about perpendicular to the parking lot center, are often caused by the asphalt expansion and contraction due to temperature changes and or this movement due to asphalt aging. Initially, these cracks will be relatively equally spaced depending on traffic but will eventually become more prevalent in the parking lot or roadway. In some cases, as these cracks become more prevalent, block cracking forms where the Transverse cracks develop into squares throughout the pavement.
Also, these cracks may extend either entirely or partially across the pavement area or roadway.
Transverse cracks begin as "hairline" cracks - or cracks up to ¼" wide - but will widen to ½" or wider with age and lack of proper repair. Because these cracks are allowing water into the pavement base and subgrade, lack of proper asphalt repair or maintenance will lead to more cracks developing parallel to the original transverse cracking. If not properly repaired, these transverse asphalt cracks will be appear with greater prevalence and the cracks will become wider; eventually, the cracks will be so prevalent that entire areas will be broken or "alligatored" (see Alligatoring section) leading to a more serious, cutting and patching asphalt repair.

Next we'll cover longitudinal asphalt cracking... 

Source: U.S.Pavement Services 

Stimulus Funds will be Awarded to All States

Every state has committed at least half its highway stimulus funds so none will lose any of its allocation, the Obama administration said Thursday.

States had until June 29 to obligate the funds or risk losing half the leftover money. Only a month ago, some 14 states had yet to satisfy that goal. Hawaii was the last to meet the mark, hitting it on June 19.

Maine has secured 100% of its funds and 15 states have more than 80% of their money committed.

 read more 

Asphalt

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The advantages of concrete curbs and gutters on parking lots and roads

Many people do not understand the use and importance of concrete curbs and gutter sections along the edges of streets, parking lots, and other pavements. The advantages of using uniform designs and standard sections are listed below.

A curb, by definition, is something that restrains; an enclosing border or edging; a raised edge or margin; a wall; or as a verb, to strengthen or confine something. As most people think of curbs, they are raised strips of concrete along the edges of streets or parking lots. The benefits of curbs have been recognized since ancient times, and stone curbs were placed along the edges of traveled ways by early civilizations. Today's concrete curbs still provide many of the same benefits, and more.

Concrete curbs or combined curbs and gutters serve several important functions. Curbs collect water from crowned pavements and convey it to points of collection, thus reducing the amount of water that gets under the pavement. They outline the edges of pavements and provide easily definable borders between traveled and untraveled surfaces. They confine pavement structures, especially if the pavements are composed of layers of materials that must be compacted in-place. Curbs help contain low speed traffic within the edges of pavements.

Besides serving the purposes listed above, curbs provide several other advantages. The neat, straight lines of curbs add to the attractiveness of parking lots and streets, and the commonly used expression "curb appeal" implies that attractiveness of adjacent properties are also enhanced by sharp demarcations between streets and lawns.

Curbs strengthen pavements. The confining of flexible pavements by concrete curbs improves compaction during construction and helps maintain the integrity of edges under traffic. The added thickness given to edges of concrete pavements by integral curbs increase strength and stiffness, reduce deflections induced by traffic loads, and therefore extends pavement life.

Curbs reduce the amount of space or right-of-way required for a street by eliminating drainage swales and their flat side slopes; curbs also reduce the lengths of driveways built from streets to homes or businesses. In some jurisdictions where both curbed and uncurbed streets are allowed by subdivision ordinances, streets with curbed sections require less dedicated right-of-way than streets without curbs, for example 50 ft for local streets with curbs, or 60 ft for local streets without curbs. The elimination of drainage swales also reduces maintenance by eliminating the cleaning of ditches, the mowing of ditch banks, and the care of culverts and their end sections that carry water under driveways.

Light reflective surfaces of concrete curbs delineate pavement edges and improve visibility for drivers at night, thus promoting safety. Where there are no concrete curbs to outline the edges of roads and streets, it is now common practice to mark the pavement edges with stripes of white paint.

Curbs improve the efficiency of street sweepers by concentrating debris for easy, mechanical pickup, as opposed to having it scattered along shoulders and drainage swales where it must be picked up by hand.

Concrete curbs have the integrity to withstand the impacts of snowplows.

A comparison of pavement sections with curbs and without curbs is shown in the figure below, illustrating the advantages in land use provided by concrete curbs. It should be noted that most of the advantages listed above pertain only to concrete curbs or concrete curbs and gutters that extend down to the bottom of pavements. Adding asphalt curbs along the edges of asphalt pavements cannot provide the confinement to improve compaction or other long-term benefits.

Save thousands by properly maintaining your asphalt pavement

The benefits to consistent parking lot maintenance are clear:

• Protecting your asphalt pavement investment

• Avoiding serious liability issues to tenants, guests and customers

• Beautify the landscape and appearance

• Plus - save more than 48% over unmaintained pavement

Let's talk about Maintenance Savings and a way to free up revenue. Unmaintained (or unsealed) asphalt pavement will likely require repairs after the first two years. Furthermore, this unmaintained surface may require  overlay as early as seven years, versus fifteen years for a maintained parking area.

According to a study performed by Girish C. Dubey, chairperson of the Pavement Coatings Technology Center at the University of Nevada at Reno, maintaining asphalt pavement with sealcoat every three years saves an average of $15.25 per square yard or $152,500.00 for a parking lot averaging 10,000 square yards. This translates into more than 48% in savings over unmaintained asphalt. Maintaining asphalt with sealcoat is a small expense that secures nearly 300% increase in asphalt life as well as the aforementioned maintenance cost savings.

Parking lot maintenance is most economical when consistently performed from the outset. However, it is never too late to implement a maintenance plan that will optimize your current pavement's condition and prolong its life.

So how about you save thousands by properly maintaining your asphalt pavement for years to come? It only gets worse with time if not taken care of. Call a pavement expert to find out what you can and should be doing. 

Why do a bunch of asphalt repair when you can sealcoat?

A lot of people, I know not you...but many just wait till the asphalt is so damaged that it must be repaired with severe measures. Research and studies prove that you can save approximately half the cost of maintenance on your pavement if you sealcoat consistently from the outset.

The weather is going to be getting warmer soon and it will be time to look at pavement that needs attention. Asphalt repairs can be prevented by a simple pavement maintenance plan and sealcoating the asphalt every few years. Let's talk about sealcoating...but first the problem, then I'll provide the solution. 

Asphalt is a combination of many materials composed in a structure that allows for weather elements (such as rain), salts, and other substances to attack and break it down. As the asphalt molecules break down, much of the original benefits - including weatherproofing - are lost. This is first observed visually by the color change in the asphalt surface:from black to brownish gray.

The rate of pavement deterioration depends upon many variables including weather or climate conditions, traffic volumes and frequency of maintenance. After the visual change in color of the asphalt surface, weather, oils and other harmful materials can significantly deteriorate the pavement surface. Oils from vehicle engines, often parked stationary for long periods of time, can cause considerable damage to an unmaintained pavement surface.

Also, further deterioration of unmaintained pavement leads to minor cracks which become wider and deeper without remedy. If these cracks are not remedied, water and other harmful substances will seep into the base and damage the pavement's load bearing capacity, ultimately causing pavement failure. The effects of this are shown in serious alligatoring, rutting, and overall pavement failure. Before long, your parking lot is riddled with cracks, potholes and drainage issues that are seemingly beyond repair.

Unmaintained asphalt shows its deterioration and damage
quickly, in as little as two years, and cracks and potholes quickly develop. Once the cracking forms, lack of proper maintenance will lead to serious liability issues caused by severe potholes and your pavement investment will be in risk of complete failure. The deterioration of unmaintained asphalt happens exponentially faster than maintained asphalt and, consequently, costs much more money over time.

The Remedy/Solution every smart property owner/manager, facility manager, and business owner is doing to keep asphalt repair expenses down to free up revenue.

Sealcoat, specifically refined coal tar, is a mixture of chemicals with a structure that does not allow destructive elements to affect its properties. This material, as a protective coat for asphalt, forms a barrier to protect against weather, salts, oils, and destructive substances that lead to pavement failure. This sealant also restores the asphalt's rich black color, dramatically improving property appearance.

Potential customers' and guests' first impression is your parking lot; a fresh, new appearance will be the best
presentation no matter your industry. By consistently protecting the asphalt pavement from deterioration and from failure, you are prolonging the life of your original asphalt by as much as eight years, or almost double the expected life of an unmaintained pavement surface, without considerable investment in an overlay or other significant remedy.

Parking lot maintenance with sealcoat usually means a three to five year cycle of sealcoating, including crackfill for developing cracks later in the pavement's life cycle, which prolongs the original pavement's life as well as ensuring the appearance of your property.

By evaluating your properties' parking lots on a
necessity basis(or better yet have an pavement expert come check it out free), all parking lot concerns could be easily amortized over three to five years - effectively eliminating your parking lot concerns.

Why go through the need for asphalt repairs every few years when you can sealcoat every few years and save up to half the cost?

What do you think?

How Pavements Fail - Part 1

A variety of factors influence the life expectancy of parking lot and street pavements. Most of the Bay Area's streets and parking lots are constructed with an asphalt surface over a rock base. This type of construction is referred to as a "flexible pavement". The factors that contribute to failure for flexible pavements can generally be categorized in two
groups:

Loads:
Most arterial and collector pavement deterioration is associated with vehicle use or loads. Loads are the
vehicle forces exerted on the pavement by automobiles, trucks and buses. These forces create stress and
deformation within the pavement structure. Repeated loading creates fatigue and resulting distress in the
pavement. Excessive loading can lead to rapid deterioration of the pavement structure evidenced by cracking and distortion of the pavement surface. Damage caused by vehicles goes up exponentially with weight. A single large truck can cause as much damage as several thousand automobiles. Buses typically have an even larger load impact than heavy trucks due to the limited number of axles and tires they employ to distribute their weight.

Environmental Factors:
Surfaces that receive little use (such as local/residential streets) will eventually deteriorate due to environmental factors. Oxidation of the asphalt causes the binder to age and lose it capability to bind the asphalt. The pavement will then begin to deteriorate as evidenced by an asphalt structure that is crumbling and raveling. Other environmental factors such a frost heave and extreme heat also accelerate the deterioration of asphalt pavements.

Load and Environmental Factors Combined Result In Pavement Failure
As time passes, continual loading in the wheel paths causes the flexible pavement to wear out and lose its
flexibility. This causes the pavement to compress and stiffen forming ruts in the wheel paths. As wheel
loading continues, lack of flexibility in the pavement causes hairline longitudinal cracks to form. Continued
loading causes these cracks to grow in length, width, and depth. As the pavement surface wears due to studded tires and chains, it loses its ability to shed water. Water then collects in the ruts in the wheel paths and then in the longitudinal cracks. As the cracks deepen they eventually reach the aggregate base. Water then drains from the surface into the base. This water intrusion causes the base to soften. As the base softens, it can not support the pavement above it. Continual loading on the surface over a "mushy" base stresses the pavement beyond its ability to flex and the cracking grows into a patchwork of alligator
cracking. This additional cracking allows more water penetration. This pavement is now on its way to major
failure.

With all the rain, potholes, water penetration...it's a good time to start thinking about asphalt maintenance for 2009.

Asphalt Cracking - repairable with sealant or fill

Cracks that form in the pavement surface can allow many harmful substances - including water, salts and engine oils - into the base and subgrade, effectively leading to the failure of the pavement surface. There are many types of cracking and many causes for these differing problems. In many cases, cracks develop because of the expansion or contraction of the base or subgrade or because of voids that form between the layers or courses of pavement. These cracks can form randomly or in the following specific forms. In all cases, if repaired while still within ¼" to ½", these cracks are easily repaired and maintained.

Transverse cracking
Transverse cracking, or cracks that occur across the pavement surface about perpendicular to the parking lot
center, are often caused by the asphalt expansion and contraction due to temperature changes and or this
movement due to asphalt aging. Initially, these cracks will be relatively equally spaced depending on traffic but
will eventually become more prevalent in the parking lot or roadway. In some cases, as these cracks become
more prevalent, block cracking forms where the Transverse cracks develop into squares throughout the
pavement. Also, these cracks may extend either entirely or partially across the pavement area or roadway.
Transverse cracks begin as "hairline" cracks - or cracks up to ¼" wide - but will widen to ½" or wider with age
and lack of proper repair. Because these cracks are allowing water into the pavement base and subgrade, lack of
proper repair or maintenance will lead to more cracks developing parallel to the original transverse cracking. If
not properly repaired, these transverse cracks will be appear with greater prevalence and the cracks will become
wider; eventually, the cracks will be so prevalent that entire areas will be broken or "alligatored" leading to a more serious, cutting and patching repair.

 

 

This crack has formed across the
entire walkway. Eventually, as
moisture and other substances seep in
to the base, more cracks will form and
lead to pavement failure. 

Longitudinal cracking
Longitudinal cracking, or cracks that form down the center of the pavement surface or
roadway, usually develop due to the deterioration of longitudinal joints formed by
separate passes of an asphalt paving machine. When the parking lot is constructed, the
paving machine must make separate passes which form two lanes of asphalt; joints
develop between these two lanes because this is usually the least dense areas of
pavement and is not properly compacted. These cracks are fundamentally the same as
Transverse cracks, despite their difference in orientation, and also allow water, salts,
engine oils and other harmful substances into the base and subgrade. These
substances lead to more cracks in the pavement and eventual pavement failure around
the original Longitudinal cracks. Usually Longitudinal cracks follow the same type of size
development as Transverse cracks: starting as hairline or about ¼" cracks then
developing to larger, more serious problems; eventually, without proper repair and
maintenance, Longitudinal cracks will become more prevalent and areas, leading to
cutting and patching necessity. Block cracks also form from Longitudinal cracks.

This crack has formed at the center of a parking lot's drive
lane, at the joint of the separate passes of a paving
machine. Smaller cracks have developed around the
original crack. 

 

Asphalt Deterioration & Raveling

Deterioration is any break-down in the pavement surface allowing more serious problems, such as raveling, to
occur. The chemical structure of asphalt inherently allows many destructive elements - such as weather
elements (rain, snow); salts; oils; and other materials - to break it down. As these destructive elements break
down the pavement surface, much of the original benefits are lost (i.e., weather proofing) and the color visually
changes from rich, black to brownish grey. This deterioration, if left unattended, inevitably leads to more serious problems such as raveling and/or cracking.

Raveling is loss of pavement material from the surface downward and is caused by the loss of asphalt binder
(deterioration), ultraviolet exposure, traffic frequency, weather conditions, asphalt mix design, and compaction of
the asphalt during construction. As the asphalt binder in the pavement wears away, the appearance starts to turn
grayish from the fresh, black look of new asphalt. Also, as the binder wears away, aggregate particles begin to
break away. This begins with fine aggregate particles breaking away and, consequently, exposing the coarse
aggregate.

As the raveling begins to become more prevalent, the dislodged particles lead to a severely rough surface and
pitted areas forming where aggregate particles have been completely removed. 

Deterioration - Oil spots

These areas of serious oil spots have led to deterioration and corrosion of the pavement surface and will eventually lead to pavement failure in these areas.

Raveling

The fine aggregate particles have worn away and coarse
aggregate particles are becoming exposed.

Remedy
To avoid the ill effects of deterioration, sealcoat provides a protective ayer for the pavement that is not vulnerable to the destructive lements such as weather conditions and ultraviolet rays.
Furthermore, the sealcoat provides a uniform surface for  areas where he asphalt binder has worn away completely.
The procedure includes:
1. The area is power cleaned and oil stains are chemically treated.
2. Coats of coal tar emulsion (exceeding Government
specification RP-355E) with a latex additive and four to six pounds of silica sand for improved durability. Application
coverage rate is 0.3 gallons per square yard.

Asphalt Potholes - they're everywhere

Potholes, bowl shaped openings that usually have raveled edges and can be up to 10 inches deep, are created
when moisture seeps into the pavement and contracts or expands, weakening the pavement; as traffic drives over
these weakened areas, it eventually crumbles and breaks away. Potholes often develop from badly cracked, or
alligatored, areas of pavement. If not repaired early on, these potholes will expand and could eventually affect the
pavement foundation.

Liability Issues
Potholes create serious liability issues in parking lot and roadway areas not only because of the potential damage
to vehicles but also because of the potential trip hazard to tenants, customers, employees and pedestrians.
Furthermore, repairing potholes before liability issues arise can avoid fraudulent and unreasonable injury
settlements. Potholes can form during any season and should be repaired immediately before worsening or
causing serious injury or other damage.

Remedy
The potholes formation means that moisture and air voids have already formed under the pavement surface,
allowing the pavement to weaken and become crumbled. This means that cutting and patching will be necessary
to repair the pothole area and the surrounding broken pavement by:
1. Cutting the area square beyond the damaged area - to ensure underlying problems that have not yet
surfaced are also corrected - with a jack hammer.
2. The broken asphalt is then excavated and the base is compact as necessary to prepare for new asphalt.
3. At least 1.5" of asphalt binder and 1.5" of asphalt topcoat are installed and compacted.
4. Edges are emulsified and sanded for proper bonding.

NOTE: Jack hammering is predominantly used because of the toothed effect on the pavement, where the newly installed sphalt fits with old asphalt in the most effective way. Saw cutting is also available upon request.