UFC 3-270-04
15 March 2001
CHAPTER 8
ASPHALT UNDERSEALING
8.1. Method. Asphalt undersealing describes the injection of bituminous material under
pavements to fill minor voids caused by pumping action. Use of asphalt to fill voids greater than
1 inch (25 millimeters) in depth or to raise slabs is not recommended. Bituminous undersealing is
mainly used to fill voids about 1/2 inch (13 millimeters) deep. Only asphalt especially prepared
for undersealing should be used. Recommended asphalt should have a penetration range of 15
to 30, a softening point range of 180 to 200 degrees Fahrenheit (82 to 93 degrees Celsius), be of
suitable consistency for pumping when heated to a temperature of 400 to 500 degrees Fahrenheit
(204 to 260 degrees Celsius), and be resistant to displacement in the pavement when cooled.
8.2. Procedure. The method of placing bituminous undersealing is practically the same as that
used for cement grout undersealing. The asphaltic cement should be heated in the bituminous
distributor tank to a temperature of between 400 and 450 degrees Fahrenheit (204 to 232 degrees
Celsius). All water should be removed from beneath the slab with compressed air prior to
pumping of the hot asphalt. The tapered nozzle on the asphalt hose is driven tightly into the
drilled hole and asphalt injected under pressure. The nozzle should be allowed to remain in a
hole for approximately 1 minute after pumping ceases and pressure is reduced, then removed,
and the hole plugged. Pumping pressures should range from 20 to 40 pounds per square inch
(138 to 276 kilopascals) under normal conditions.
During pumping, water should be sprayed on the pavement adjacent to the drilled holes to
prevent discoloration of the surface. Water saturated with hydrated lime is considered most
suitable, since spilled asphalt will chill quickly and can be easily removed. Asphalt seeping
through cracks or joints can be quickly chilled and hardened by applying cold water. Extreme
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