Lesson 1/Learning Event 2
Learning Event 2
TYPES AND GRADES OF ASPHALT
Asphalt is a natural or manmade by-product of petroleum distillation. Natural asphalt is found in
nature as either lake (or pit) asphalt or rock asphalt. There are three types of asphalt:
Asphalt cement is a solid. The Corps of Engineers specification covers three (3) types of asphalt
HARD: for hot climates (Egypt, Arizona, Texas)
40-50 Penetration or AP-7 or AC-40
60-70 Penetration or AP-5 or AC-20
MEDIUM: for moderate climates (Virginia, Missouri, Kansas, Germany)
85-100 Penetration or AP-3 or AC-10
120-150 Penetration or AP-1 or AC-5
SOFT: for cold climates (Alaska, Maine, Minnesota)
200-300 Penetration or AP-00 or AC-2.5
Each grade is designated by a penetration grade or AP or AC numbers.
The special equipment needed to heat asphalt cements is not always available. Since asphalt
must be in a fluid condition to spray or to mix with an aggregate, the solid asphalt cement would
not be suitable. A more fluid asphaltic material requires less heating than asphalt cement to
secure proper spraying and mixing consistencies. This is obtained by combining an asphalt
cement with a petroleum distillate. The distillate used is called a "cutterstock" and the product of
the combined materials is called "asphalt cutback."
Upon exposure to atmospheric conditions the distillates evaporate, leaving the asphalt cement to
perform its function. This rate of evaporation deter mines the type of asphalt cutback.
Rapid-Curing (RC). Composed of asphalt cement and a gasoline or naphtha with a
curing time of 4 to 8 hours.
Medium-Curing (MC). Composed of asphalt cement and a kerosene or JP-4, with a
curing time of 12 to 24 hours.