Lesson 2/Learning Event 1
Estimation for Plant Mix
To determine the total tonnage of plant mix required for a given paving area, the compacted
volume in cubic feet is multiplied by the unit weight of the mix in pounds per cubic foot. Unit
weight may be determined with the Marshall Method, as described previously. When the exact
unit weight of a plant mix has not been determined, an estimated weight of 160 pounds per cubic
foot may be used. (Unit weight is usually between 140 pounds and 160 pounds compacted cubic
foot.) The formulas used for this method of plant mix are:
Binder: tons of plant mix x OCA = Tons of AC
Aggregate: Tons of plant mix-tons of AC = Tons of
Aggregate (AGG)
where:
L = length of paveed area in feet
W = width of paved area in feet
LF = loss factor, if it is known
FCT = final compacted thickness in inches or the depth of the pavement in inches after the
completion of all compaction operations
UW = the exact unit weight of compacted plant mix in pounds per cubic foot
24,000 = 2000 x 12 or pounds per ton and inches per foot conversion factor
Example: A 2-inch thickness of plant mix is desired on a 110 foot by 650 foot parking lot. Find
the tons of plant mix required for this project if the unit weight of plant mix is 147
pounds per cubic foot.
SOLUTION:
L = 650 feet
W = 10 feet
FCT = 2 inches
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