Find the amount of asphalt required for this project.
Solution:
Estimates for Asphalt Plants
The amount of materials comprising the plant mix
can be best determined by a proportionate method. This
is demonstrated by the following example:
Example: The required tonnage of plant mix for a
project is 800 tons. The aggregate blend is 50/40/10
(percentage coarse aggregate/fine aggregate/mineral
filler). The bitumen content is 6 percent. How many tons
of each aggregate are required?
The job mix formula is as follows:
= Adjusted Percent of AGG
OAC = Optimum Bituminous (Asphalt) Content
Solution:
Total aggregate percent by weight= 100 – 6 = 94
percent, or 0.94.
Coarse/aggregate = 0.94 x 50 percent = 47.0 percent
by weight of the total mix.
Fine aggregate = .094 x 40 percent = 37.6 percent
by weight of the total mix.
Mineral filler = 0.94 x 10 percent = 9.4 by weight
of the total mix.
To convert to tons, multiply the required tonnage of
plant mix by the percentage of each component of the
mix. The results should be adjusted so that the sum of
the tonnage of components is equal to the required
tonnage of plant mix.
Coarse aggregate = 800 x 0.470 = 376.0 tons
Fine aggregate
= 800 x 0.376 = 300.8 tons
Mineral filler
= 800 x 0.094 = 75.2 tons
Bitumen
= 800 x 0,060 = 48.0 tons
800 tons
(The bitumen weight was calculated as a check.)
Tons per hour
The equation used to compute the amount of asphalt
that can belayed with a paver per hour is as follows:
Tons per hour =
L x W x D x 146
2000
x 6 0
Where:
L
= Feet per minute. The NCF uses 11 feet per
minute for planning purposes,
W
= Width of the paver screed
D
= Depth or thickness of compacted mat
146 =This number represents the approximate
weight of 1 cubic foot of compacted
hot-mix asphalt
60
= 60 minutes in one hour
2000 = There are 2,000 pounds in 1 ton
Example: The required tonnage of hot-mix asphalt
for a project is 800 tons. The screed of the paver is set
at 10 feet, and the depth of asphalt is 2 inches. Estimate
the amount of asphalt that can be laid per hour.
Solution:
11 x 10 x .167 x 146 x 60 = 160921.2
2000
2,000
160921.2
2,000
= 80.46 tons per hour
By planning and estimating the amount of hot-mix
asphalt that can be laid per hour, you are able to tell the
asphalt plant exactly how much hot-mix asphalt is
required to be delivered per hour and/or per day.
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