1) As a materials engineer working for a highway department, what standard PG asphalt binder grade would you specify for each of the conditions shown in Table 1 (show all calculations and fill in the table)?
Table 1
|
Case
|
Seven-Day
Pavement Maximum
Temperature, °C
|
Minimum Pavement
Temperature, °C
|
Recommended PG Grade
|
|
Mean
|
Std. Dev., °C
|
Mean
|
Std. Dev., °C
|
50% Reliability
|
98%Reliability
|
|
1
|
42
|
2.5
|
-30
|
2
|
|
|
|
2
|
51
|
3
|
-18
|
4
|
|
|
|
3
|
65
|
2
|
10
|
3
|
|
|
2) The log(flexural creep stiffness) versus log(time) data collected in the BBR test at -18°C is automatically fit by the BBR software with a second order polynomial as follows:
log[S(t,T)] = A + B[log(t)] + C[log(t)]2 A T)]
Derive an equation to solve for the creep rate, m, the slope of the log stiffness-log time curve. To derive the equation for m, solve the following derivative:
Then use your equation to solve for m for a binder at -12°C with A = 5.721, B= -0.036521, and C= -0.0914. Don't forget to take the absolute value, as shown above. Note on units: time, t, is in seconds, and S(t,T) is in kPa.
Also, plot S(T,t) versus time on a log-log scale, and show your computed m-value as a tangent line to the curve at t=60 seconds. Plot the original data on log axes. In other words, do not take the log of the data and plot the "logged" data on arithmetic scales, because it is hard to interpret when plotted this way.
3) Binder Conformance. Check each of the following sets of test results to determine if the binder tested conforms to the intended PG binder grade. Indicate with the word "Pass" or "Fail" in the last cell of each column of the following table your conclusion, and circle any test results which failed to meet spec criteria. Assume correct test conditions were used (temperature, load freq's, etc.). Use Table 9.3 from M&Z at end of assignment to help.
4) Binder Classification (Grading) What is the best possible PG grade of the asphalt whose results are shown in Table 4 below? Use Table 9.3 from M&Z at end of assignment to help.
5) Given the following DSR data for asphalt that has been treated in the pressure aging vessel:
a) Compute the complex dynamic shear modulus, G*
b) Compute G* sinδ
c) Would this binder pass the Superpave fatigue cracking criteria?