Asphalt Pavement

What Is Asphalt?

Asphalt is a mixture of aggregate (stone and sand), and is sticky asphaltic binder (sometimes referred to as tar). It is usually black in color, and is applied in a thick layer (or layers) as paving for driveways, parking lots and roads. Asphalt is one of the world’s most ancient engineering materials. The ancient Sumerians used it as early as 6,000 BC.

Although asphalt can be naturally occurring (the LaBrea tar pit in Los Angeles contains natural asphalt deposits), most asphalts today are refined from crude petroleum and are mixed with aggregates, heated and blended in a batch plant. The asphalt is then hauled to the paving location where it is spread to a uniform depth, and rolled over a prepared base (usually of stone), until compacted. The thickness of the asphalt depends upon the amount of traffic and the average weight of the vehicles that will be driving or parking over the surface. A residential driveway may have as little as two inches of asphalt (because of light use), while a major highway may have eight inches or more of asphalt. Asphalt should be laid when temperatures are 45 degrees Fahrenheit and rising. 

The life of an asphalt surface is generally seven to twenty years, and though it seldom “wears out” and it eventually becomes deteriorated by environmental factors. Asphalt binder, which glues the pavement together, is a flexible material which over years loses elasticity and dries out from the sun rays and exposure to oxygen. This drying out causes the aggregate stone to be expelled from the base and “raveling” occurs. Drying also causes cracks which in turn allow water to penetrate the asphalt and erode its base, causing more cracking and (if cracks are not filled) potholes. “Freeze and thaw” expands and contracts the pavement, causing cracks. Chemicals, gasoline, oil and other compounds penetrate and soften asphalt, causing deterioration. The best way to control deterioration and to expand the life of asphalt is to fill cracks and potholes as soon as they appear and to institute a program of protective crack filling and sealcoating.

*Trivia Note: The first asphalt used as pavement in the U.S., was imported to make Philadelphia sidewalks in 1838. The first U.S. asphalt road was laid in Newark, NJ in 1870.

Types of Asphalt & Repairs

How to Decide What to Do?

The Objective

No matter what the budget, your objective is to keep water from getting under the asphalt base, and from penetrating to (and moving around) underlying rocks that support the pavement. Water is the enemy!

The Problem

Asphalt is the best choice for parking lots and/or roads.It is both resilient and repairable. The problem arises because the sticky black binder that holds asphalt’s rock/aggregate together, begins to deteriorate and dry out the moment it is laid. Small surface cracks appear in the first year or two. Without attention, little cracks explode into big cracks. Unattended big cracks will allow water into the gravel/rock sub-base, which supports the asphalt. Water will weaken and move the gravel/rock sub-base around, creating voids under the asphalt. The weight of the cars and trucks riding over an unsupported asphalt surface will cause the surface to collapse. This will lead to potholes and other types of pavement distress will result. Un-repaired potholes and distressed areas will grow bigger as more water pours under the base, and traffic gnaws away at the jagged edges.

The Solution

A regular program of asphalt maintenance is the answer! Although un-maintained asphalt deteriorates significantly within six years, maintained asphalt may be in excellent condition into its second decade.

Below are some maintenance options:

Solution I-Crack Filling

A most prudent and efficient choice, is to start a regular, yearly program of crack filling. Crack filling will save a “bundle” in the long run. Swift uses hot, rubberized crack fillers that exceed federal specifications. (Cold and non-rubberized crack fillers do not seal cracks. Always specify hot, rubberized crack filler.) Note: Even our premium crack filler doesn’t last forever; through freeze and thaw it will eventually be expunged, and will need to be reapplied.

Solution II-Sealcoating

Rich, black federal spec, sealcoat will help seal the sticky asphalt binder from: the drying of oxygen and sun the erosion of oil and gas, and from water damage.

Solution III-Excavation and Replacement of Asphalt

The most desirable and surgical type of repair for potholes and severely compromised areas (e.g. alligator areas that resemble puzzle pieces, or extremely eroded pavement), is excavation and replacement. Asphalt is cut out (down to base) with a diamond-blade circular saw, or jack-hammer. The area is squared-off (squaring edges forms the strongest patch). Asphalt debris is removed. The rock base is stored and hot asphalt is applied and compacted to the same level (grade) as the surrounding pavement. Edges are tacked down with hot tar. Edges do not break off easily from rolling traffic, since the repair is the same level as surrounding pavement. Excavation and replacement is the most permanent and strongest repair available. It goes to the root of the problem and solves it, rather that treating the symptoms. Excavation and replacement is significantly more expensive than the overlay repair described next, but many of our clients choose excavate and repair exclusively. 

Solution IV-Overlay Patch 

An appropriate type of repair for many situations is the overlay patch. Hot asphalt is placed over the deteriorated area, and edges are feathered to overlap the surrounding pavement. The patch corners are squared, the asphalt is compacted, and edges are tacked down with hot tar. An overlay patch may be a good choice when deterioration is minor, and the base asphalt is not yet compromised. Overlay patches are much less expensive than excavation and replacement repairs. When pavement problems are severe, overlay patches are a temporary solution. In an overlay repair, old corrupted asphalt is not removed (except for loose pieces). New asphalt is placed right on top of the old pavement problem, and traffic will massage the new patch into old topographical irregularities, causing the underlying problem to eventually “reflect” and reappear. Remember though, that your objective is to keep water out of the pavement base, and if you’re dealing with a limited budget, go ahead and do overlay repairs. They’re somewhat temporary, but effective. Metaphorically speaking, it’s a good idea to protect yourself from the elements by erecting a tent (if that is all your budget allows). You can plan to build a house later. A caution about overlay patches…They sit above the level (grade) of your existing pavement, and the slight rise in elevation that patches cause, may affect drainage patterns, causing water to shift and pool on another part of the pavement. (Swift uses hot asphalt. Cold asphalt provides only the most temporary type of repair and will not last ... always choose hot asphalt. Cold patch; however, does have an application in filling extremely wide cracks.)

Solution V -Whole Lot Overlay

If your entire lot is compromised, consider a whole new asphalt surface. Potholes and cracks should be fixed to prepare your asphalt for at least 1.5 inches of fresh asphalt. It will be like new.

Solution VI -Drain Installation

If you have severe drainage problems, fixing the asphalt may not be enough; you may need a drain installed. Swift will be happy to consult on drainage requirements. 

Solution VII -New Construction

If your parking lot is “Past the point of return”, Swift has the capability to entirely replace it. If you’ve never had a asphalt lot, Swift can install one. Typical commercial construction consists of excavating and grading the area to be paved, putting down base stone, laying one or more courses of base asphalt (depending upon expected usage and vehicle weight), and finishing with a course of top asphalt.

Troubleshooting

You may have a unique asphalt challenge that cannot be cured by the traditional means outlined above.