(CH 8) Estimate the total direct cost for furnishing materials and placing a hot
ID: 1713043 • Letter: #
Question
(CH 8) Estimate the total direct cost for furnishing materials and placing a hot-mix asphaltic concrete pavement overlay 10.0 miles long, 24 feet wide and 4 inches thick. The pavement will be placed in 2 layers, each 2 inches thick after compaction. Use the same equipment costs and wage rates as those used in Example 8.5. The compacted asphaltic concrete will weigh 440 pounds per square yard. .The asphalt plant will control the production with a production rate of 250 tons per hour. Use a 50 minute effective hour. Round the time required to a full 8-hour day. The asphalt cement percentage of combined aggregate weight is to be 5%. Allow a 2% waste factor Allow a 6% waste for the coarse aggregate and a 10% waste for the fine aggregate. Prime Coat Materials $1.90/gal. The cost of fuels and lubricants for the asphalt plant $1,560.00 per hour 16 haul trucks will be used to haul the asphaltic concrete to the paver. Coarse aggregate $24.50/ton · · .Fine aggregate- $22.75/ton Asphalt cement- $280.00/ton Prime coat- $3.25/gallonExplanation / Answer
Quantity of materials:
1mile = 5280 feet
1 sq.ft = 0.111 sq. yard
Total surface area = (10 miles x 5280 ft) x 24ft = 1267200 sq.ft x 0.111 sq.yd = 140659.2 sq.yd
1 inch = 0.083ft and 1ft = 0.33 yd and 1lb = 0.005 T
2 inch = (2inch x0.083 ft) = 0.166 ft x 0.33 yd = 0.055 yd
Material for 2 inch base course = 0.055 x 140659.2 x 440 lb/sq.yd = 3403952064 lb x 0.005 T = 1702 T
Material for 2 inch wearing course = 1702 T
Total aggregate weight = 1702 x 2 = 3404 T
Since asphalt cement % of combined aggregate weight is 5%,
Effective weight of aggregate = 0.95x3404 = 3233.8 T
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Material quantities for cost:
Coarse aggregate (60% with 6% waste) = 0.6 x 3233.8x 1.06 = 2056.7 T
Fine aggregate (40% with 10% waste) = 0.4 x 3233.8 x 1.1 = 1422.9 T
Asphalt cement (5% with 2% waste) = 0.05 x 3233.8 x 1.02 = 165 T
Prime coat = surface area x 0.3 gal/sq.yd = 140659.2 x 0.3 = 42197.76 gal
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Production time for asplalt mix plant:
For a 50min hour, plant production rate = (50min/60) x 250 T/hr = 208 T/hr
Time to complete the work = (3404 T/ 208 T/hr) = 16.34 hr
Rounding to full 8 hour day, total time = 24 hr
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Production time for transporting asphalt mix:
Cycle time for a truck:
Load: 20 T / 208 T/hr = 0.1hr
Haul: 9mi / 30mph = 0.3 hr
Dump: 12min / (1hr/60) = 0.20 hr
Return: 9mi / 35mph = 0.26 hr
Total cycle time = 0.86 hr/trip
Quantity of asphalt mix/trip = 20T/trip x (1trip/0.86hr/trip) = 23.26 T/hr
For 45min hr, asphalt mix hauled/trip = 23.26 T/hr x (45/60) = 17.45 T/hr
Required truck = plant production/truck production = 208/17.45 = 12 trucks
16 trucks are available. Hence OK
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Cost to construct the pavement:
Material cost:
Asphalt cement: 165 T x 280 = $ 46200
Coarse aggregate: 2056.7 T x 24.5 = $ 50389.15
Fine aggregate: 1422.9 T x 22.75 = $ 32371
Prime coat: 42197.76 gal x 3.25 = $ 137142.72
Total material cost = $ 266103
Equipment cost and wage cost as used in Example 8.5
Total equipment cost = $ 1313470
Total wages = $ 359424
Thus total direct cost is the sum of material, equipment and wage cost = 266103+1313470+359424 = $ 1938997
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