Repeat Problem 19-7 using two different depths of untreated aggregate bases of 6 in. and 12 in. Assume a structural coefficient of 0.12 for the base course. Highway contractors in your area can furnish rates for providing and properly laying an asphalt concrete surface and untreated granular base. If these rates are available, determine the cost for constructing the different pavement designs if the highway section is 5 miles long and the lane width is 12 ft. Which design will you select for construction? Problem 7 A section of a two-lane rural highway is to be realigned and replaced by a four-lane highway with a full-depth asphalt pavement. The AADT (both ways) on the existing section can be represented by 500 ESAL. It is expected that construction will be completed five years from now. If the traffic growth rate is 5% and the effective CBR of the subgrade on the new alignment is 85, determine a suitable depth of the asphalt pavement using the AASHTO method. Take the design life of the pavement as 20 years. The resilient modulus of the asphalt (EAC) is 400,000 lb/in2 . Assume mi for the subgrade is 1 and the percent of traffic on the design lane is 45%. Assume the design serviceability loss is 2.0, a reliability level of 90% and a standard deviation of 2.0.