TM 5-822-10/AFM 88-6, Chap. 6
(6) It is desirable to change the properties of the asphalt in the top approximate % inch of material so that the
asphalt cement approaches its original properties. Test results have shown that the viscosity test is more effective in
determining a change in asphalt properties than the penetration test. Although application of a small amount of rejuvenator
will be reflected by the viscosity test, the penetration test may indicate very little or no change in asphalt property.
(7) Rejuvenators should be applied in hot weather, above 70 degrees F, so that the rejuvenator will penetrate more
deeply into the asphalt pavement and will cure sooner.
b. Application of rejuvenators. When applying a rejuvenator, the following must be considered.
(1) The asphalt distributor is the key piece of equipment used to apply asphalt rejuvenators. It is essential that the
distributor is in proper operating condition when rejuvenators are applied to ensure that the rate of application is uniform.
Figure 2-2 shows a distributor properly applying a rejuvenator to an asphalt concrete pavement. An inspection of the
distributor should ensure that:
(a) The distributor has a circulating tank so that the rejuvenator can be thoroughly mixed prior to spraying.
(b) The motor is in proper running condition so that it does not misfire when accelerating and cause varying rates
of rejuvenator to be applied.
(c) The size of the spray nozzles is selected so that a smooth consistent spray is obtained over the range of
desired application rates.
(d) All spray nozzles are the same size and are set at the same angle with the spray bar.
(e) The spray bar is at the correct height to provide either a double or triple overlap.
(2) Before rejuvenator is applied to the pavement, several test sections should be constructed and the rejuvenator
should be applied to the sections at various rates to determine the proper application rate. Generally, the application rate
should not exceed that which will allow the rejuvenator to penetrate the pavement within 24 hours.
(3) The amount of rejuvenator needed to properly modify the asphalt binder may not be the same amount needed
to penetrate the asphalt pavement. The determinations made from the test sections should dictate the amount of
rejuvenator that can penetrate the asphalt pavement, and this amount should never be exceeded. The optimum benefit will
be obtained by applying the maximum rate that will penetrate the pavement.
(4) When rejuvenator is applied to the pavement, clean dry sand should be available to blot areas that received too
much rejuvenator. The sand should be evenly spread over these areas, broomed into a pile, and removed. Rolling the
pavement surface 1 or 2 days after rejuvenator has been applied may help to knead and to close hairline cracks.
2-4. Heater-planing-scarifying.
a. Heater-planing. Heater-planing consists of heating the surface of a bituminous concrete pavement and planing the
surface to the desired grade. In recent years, the cold-milling operation has essentially replaced heater- planing for airfield
work.
b. Planing operation. The planing operation may require one or more passes of the equipment to obtain the desired
depth of cut. The equipment used to plane a pavement varies considerably. Some of the equipment, as shown in figure
2-3, is self-contained so that one piece of equipment can heat, plane, scarify, or add binder and hot mix. Other equipment
is not self-contained. In fact, often planing and scarifying are done with several pieces of equipment, such as a heater
which can heat and scarify, a planer, which usually is a motor grader, a distributor to add binder material, and a laydown
machine. A heater-planer with scarifying teeth followed by a grader is shown in figure 2-4. Usually, when planing and
scarifying are required, several passes may be necessary to plane the pavement to the desired depth before scarification.
The planed pavement is then reheated and scarified to a depth of to 1 inch. Some planers use direct flame to heat the
pavement surface, and others use radiant heat. The heater in figure 2-4 uses direct flame for heat, and the heater in figure
2-3 uses radiant heat.
c. Planing pavement. Caution should be used when planing an existing pavement to a desired grade. Since the planing
operation usually consists of removing the heated material to a design grade, an experienced operator is required. Two
to three passes of the heater and planer may be necessary in some areas to obtain the desired grade.
d. Removed material. The removed material can be used best while hot to provide a low-quality bituminous mixture
where a low-quality mix is acceptable. Kerosene or other solvents are often mixed with the removed material to form a
cold mix that can be stockpiled. Often, the quantity of material removed is so small that it is impractical to use the planed
material. Also, once the material cools and hardens, it is difficult to reuse.
e. Scarifying process. Scarifying the pavement surface prior to overlay can minimize some existing pavement
problems such as bonding if the pavement surface has become polished over a period of years from the action of traffic.
In this case, the surface can be scarified to promote a good bond between this existing polished surface
2-3
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