There are numerous methods available for asphalt pavement preservations, but the trick is to utilise the most cost-effective methods available.
With the proven performance of asphalt rejuvenators to revive an aging pavement, more and more pavement engineers are utilising rejuvenators to economically extent the asphalt pavement life. This type of treatment has the potential to extend the life of an asphalt pavement for several years beyond the point where rehabilitation, or major reconstruction would be required, thus significantly reducing the pavements annual maintenance costs.
Asphalt binders, the bitumen in the HMA, can be fractioned into two subdivisions, ie., asphaltenes and maltenes.
Asphaltenes are defined as that fraction of the asphalt insoluble in n-pentane (solvent) and its function is serve as a bodying agent.
Maltenes is the collective name for the remainder of the asphalt material left after the precipitation of the asphaltines.
During the process of weathering or oxidation, the ratio of maltenes to asphaltens is reduced with the result being a dry and brittle pavement. In order to reverse the aging process of asphalt, one must successfully penetrate the pavement to a limited depth and restore or improve the maltenes to asphaltenes balance.
Using rejuvenators on a new pavement does not seem to be logical at first glance. However, it has been established that the greatest change in composition of an asphalt binder takes place during the manufacture of the Hot Mix Asphalt (HMA).
Applying a rejuvenator to a new surface a few weeks after it has been laid, does several things to the pavement. Besides restoring the original asphalt properties that were lost in the HMA manufacture, the chemical assists in sealing the pavement as well as in improving the durability of the surface course.
Maintenance can be subdivided into preventative and corrective maintenance. We will concentrate on preventative maintenance. This should be applied to pavements at the first signs of aging of the surface course, pitting, ravelling, shrinkage and cracking. Some pavement engineers maintain that preventative maintenance should begin before any of these signs occur. However, starting a maintenance program can become a costly exercise. Nonetheless, applying the rejuvenator at periodic intervals can restore the asphaltene-maltene balance so essential to maintain a ductile, pliable pavement.
Differences between surface rejuvenators and fog sprays
There are significant differences between surface rejuvenators and fog sprays. Surface rejuvenators penetrate the existing bituminous surface and improve the properties of the aged binder. Fog seals, which normally consist of bitumen emulsion, penetrate to a very limited extent, and remain as a bituminous film on the surface. Fog sprays are mainly used on chip seal surface treatments, to reduce chip loss.
Selecting suitable road pavements
Road pavements that exhibit the following modes of mild distress will benefit from the application of SRM Rejuv
- Dry asphalt pavements that show minor ravelling
- Asphalt pavements with minor hair cracking caused by ageing of the binder
- Chip seal surface treatments that exhibit minor chip loss
Pavements that exhibit severe levels of distress are unlikely to benefit, in particular:
- Crocodile and map cracking
The minimum road temperature at the time of application is 15oC and rising. Application should not be carried out when rain is likely within the next 5 hours.