The True Story of Rejuvenation

by Asphalt Systems, Inc. of Ohio
Salt Lake City, Utah

Recognizing many years ago that preventive maintenance is much less expensive and much more satisfactory than corrective maintenance, Asphalt Systems, Inc. of Ohio was organized to research and explore methods of providing the most effective preventive maintenance for asphalt pavements.

ASPHALT DETERIORATION

All organized matter on earth is in a continual state of deterioration back toward the basic elements where stability is achieved. Some organizations of matter deteriorate much more rapidly than others. Asphalt happens to be one of those materials that deteriorates quite rapidly and in recent years deterioration of asphalt has even accelerated due to advancements in the petrochemical refining process that allow a more complete extraction from the asphalt of many formerly beneficial elements that are now being used in other markets. The asphalts used today, which are the very end residue of the refining process, have significantly more essential elements removed from them than ever before. We can anticipate this trend to continue in the future and even become more acute, especially when we consider that the elements being extracted are usually high profit materials for the refining companies, and asphalt itself is a very low profit item.

Asphalt pavement consists of sand, gravel and asphalt binder. The sand and gravel are usually not significant factors in pavement deterioration. It’s the glue that binds the aggregate together that breaks down and causes our ever so familiar pavement failures. The aggregate literally comes unglued. Therefore the answer to asphalt pavement maintenance is, in basic terms, very simple - SAVE THE BINDER AND YOU SAVE YOUR PAVEMENT.

Asphalt is a hydrocarbon, that is, it consists of hydrogen and carbon atoms, but the arrangement of hydrogen and carbon atoms in the molecules vary widely depending upon the source of the crude oil from which it was derived and the processes involved.

The essential portions of asphalt are resins, oils and carbon. The carbon is fixed. It provides the body, the strength of a pavement. It does not deteriorate significantly in our lifetime and is not a major factor in asphalt pavement deterioration. The resins provide the glue, or binding ability of an asphalt pavement, and the oils provide the flexibility necessary to give and rebound under the weight of heavy vehicles. It is the oils and resins that deteriorate causing pavement failure, so these two ingredients are our prime considerations in preventive maintenance.

As the oils break down and cook out of a pavement, the pavement loses it’s flexibility and part of it’s mass. The result is shrinkage cracks and stress cracks caused by heavy vehicles and natural ground movement, as well as expansion and contraction from temperature variations which, during the spring and fall in some areas, can vary as much as 40 degrees or more within a 24 hour period.

To illustrate the importance of keeping the oils in the pavement, let’s compare asphalt pavement to a strip of bacon. When you take a fresh strip of bacon out of it’s package it is extemely flexible, you can tie it in knots. But when you put it in a pan and cook the oils out it becomes brittle and breaks easily. Asphalt pavement also breaks when the loss of oils destroys it’s intended flexibility.

THE GSB SOLUTION

A very effective and relatively inexpensive solution to these problems was found in a naturally pure hydrocarbon commonly known as Gilsonite, but more properly named Uintaite, found only in eastern Utah. Gilsonite occurs in vertical veins extending as deep as half a mile in cracks as wide as 15 feet in solid sandstone. It is hard and brittle and is naturally very resistant to oxidation. It is completely compatible with asphalt and naturally possesses virtually all of the characteristics we were looking for in a preservation material. Gilsonite is 45 percent resin, naturally very high in anti-oxidants, polar compounds, anti-stripping chemicals and has a high affinity, or attraction, to all kinds of aggregates. It contains about two and one half times the amount of basic nitrogen as the average refined asphalt, and has superior anti-striping and adhesion characteristics. Unlike refined asphalts nothing is removed from the Gilsonite in the process of manufacturing GSB products, but some other important ingredients are added. Gilsonite, by itself, does an excellent job of restoring resins to a pavement but contains little oil. For that reason select oils and plasticizer are added to Gilsonite in GSB products to restore flexibility to the asphalt as well as rebinding the aggregate.

The resins which glue the aggregate together in an asphalt pavement break down due to oxidation and the damaging rays of the sun. The aggregate literally comes unglued. We call this condition raveling. Although GSB products and procedures are primarily designed to be used as preventive maintenance treatments, they also provide some corrective value for certain conditions. Raveling is one problem that GSB products can correct in many cases by the reintroduction of resins to the oxidized pavement, thereby regluing the surface aggregate and providing a protection from further oxidation.

In order to be truly effective, preventive maintenance procedures must have the ability to replenish the oils and resins and be able to seal in those oils and protect the resins by sealing out sunlight, air and water; and to be of any lasting value it must do so in the pavement rather than on the pavement so that traffic abrasion does not destroy the seal.

There are several products on the market claiming to be asphalt pavement rejuvenators. Most of them are essentially oils which do replace lost oils in the top one quarter inch or so of a pavement, but contain little or no resins. If pavement rejuvenation is a major factor be sure you select a material that restores resins, anti-oxidants, polar compounds, and anti-stripping chemicals as well as oils. Replacing oils is only part of the job of pavement rejuvenation.

SUMMARY

GSB products are primarily designed to be used on asphalt pavements within the first few years of their existence to provide many of the elements lost to asphalt cement during the refining process, and as a preservative in retarding the natural oxidation process. They can also be effective in solving specific pavement problems such as raveling and oxidation. Occasionally GSB may be effective in aiding to extend the useful life of a badly deteriorated pavement until funds can be obtained for reconstruction. It should be remembered however, that it is significantly more cost effective to prevent most asphalt pavement problems than it is to correct them. Timing is everything in preventive maintenance: it should be done before failure occurs. An attitude of preventive maintenance is long over due in the Asphalt Pavement Industry. We at Asphalt Systems, Inc. of Ohio have been in the Asphalt Preventive Maintenance business for over twenty-five years. Our materials are years ahead of the industry standards and they address the very real problems of today’s asphalt pavements. We would be pleased to demonstrate the effectiveness of these materials for you. Simply notify your local GSB distributor, or call 1-800-729-8094.

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