Determination of Creep Compliance and Tensile Strength of Hot-Mix ...

small range (the difference between the maximum and minimum values) of creepcompliance per temperature can produce problems in the algorithm used to createthe master creep compliance curve (the full explanation of which is beyond thescope of this paper) by limiting the amount of overlap created when the -10°C andthe 0°C creep compliance – time curves are shifted to the right in time to extend the-20°C curve thereby creating one continuous, creep compliance – reduced timemaster curve. The general process is shown in Figure 11 using the 07-123 datacalculated using the original method.1.000Creep Compliance Master CurveCreep Compliance (1/GPa)0.100Shift RightShift RightOverlapOverlap-20 Deg C: Reference Temperature0.0101.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06Reduced Time (seconds)-20 Deg C -10 Deg C 0 Deg CFigure 11: Creep Compliance Master Curve CreationThis conclusion was reached using two different types of analyses: one was basedon creep compliance values calculated using a different method for determining t zero ,and the other was based on arbitrarily increasing the range of creep compliancevalues for the 07-123 mix at -10 and 0°C.The alternative method for determining t zero is based on an “equivalent area” conceptwhere at some time, t, the area under the load versus time curve of a noninstantaneousramp load is equal to the area under a true creep load profile at time,t′. This concept was first suggested to the authors by James Sherwood of theFHWA. Later, Harold Von Quintus verified that this concept has been used in thepast, particularly in an earlier flexible pavement analysis program called VESYS.23