Civil Engineering Reference
In-Depth Information
9.33 The Marshall procedure was used to design an asphalt concrete mix-
ture for a heavy-traffic road. Asphalt cement with a specific gravity
of 1.025 is to be used. The mixture contains a 19 mm nominal maxi-
mum particle size aggregate, with bulk specific gravity of 2.654. The
theoretical maximum specific gravity of the mix is 2.480 at 4.5% as-
phalt content. Trial mixes were made, with the average results
shown in Table P9.33. Determine the optimum asphalt content using
the Asphalt Institute design criteria. Assume a design air void con-
tent of 4% when using Table 9.14.
Table P9.33
Asphalt Content,
Bulk Specific
% by Weight
Gravity
Stability, kN
Flow, 0.25 mm
3.5
2.367
8.2
7.3
4.0
2.371
8.6
9.4
4.5
2.389
7.5
11.5
5.0
2.410
7.2
12.5
5.5
2.422
6.9
13.2
9.34 Describe the process for determining the stripping potential for an
asphalt concrete mix.
9.35 Briefly discuss how the indirect tensile resilient modulus is deter-
mined in the lab.
9.36 The resilient modulus test was performed on an asphalt concrete
specimen and the following data were obtained:
Diameter
=
4.029 in.
Height
=
2.497 in.
Repeated
Sum of recoverable horizontal
load
=
559 lb
10
-6
in.
deformations
=
254
*
Assuming a Poisson's ratio of 0.35, calculate the resilient modulus.
9.37 State six advantages of recycling asphalt pavement materials. Why
can we not mix the RAP materials with aggregates in a conventional
hot-mix asphalt concrete plant? Show the proper ways of recycling
the RAP materials in the two types of hot-mix asphalt plants.
9.38 State four different asphalt modifiers that can be added to asphalt or
asphalt mixtures, and indicate the effect of each.
9.39 When is portland cement used in asphalt concrete?
9.40 During construction of the HMA layer of asphalt pavement, cores
were taken at random after compaction to detect any construction
problem and to ensue that the density is within the specification lim-
its. The target value was set at 148.2 pcf and the upper and lower
specification limits were set at 148.9 pcf and 147.5 pcf, respectively.
The density data shown in Table P9.40 were collected.
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