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March 2019

IDEAL-CT & Hamburg Wheel Tracker meet the need for crack/rut balanced performance testing in asphalt mixes

By | Asphalt | No Comments

ACE XP shows 30% to 50% improvements in both tests

 Indirect Tensile Cracking Test at Intermediate Temperature (IDEAL-CT)

Figure 1. Indirect Tensile Cracking Test at Intermediate Temperature (IDEAL-CT)

Asphalt pavements need to be stiff enough to minimize rutting, but resilient enough to bend without breaking to prevent cracking. The trend over the last 20 years has been one-sided — fixing the ruts at the expense of the cracks. Many in the industry have begun to recognize the need for a “balanced approach” to developing pavement designs that will perform well in resisting both rutting and cracking.

There are seven key existing performance or index tests for asphalt cracking (see Table 1). These tests vary in complexity and cost, and as a result, the asphalt industry has not traditionally performed cracking performance tests on every project.

Hamburg Wheel Tracker (HWT) Test

Figure 2. Hamburg Wheel Tracker (HWT) Test

For rut testing, the Hamburg Wheel Tracker (HWT) test tends to be the most widely used method. However, many agencies and specifiers, including DOTs, are moving toward adopting performance-based specifications where both mix designs and daily production will need to meet certain minimums in both cracking and rutting parameters in order to be considered.

A new and promising cracking test has recently been developed by Dr. Fujie Zhou and his colleagues at the Texas A&M Transportation Institute. The Indirect Tensile Cracking Test at Intermediate Temperature (IDEAL-CT) is a reduced cost method that provides consistent results to predict field performance in cracking. This test, along with HWT, can be used daily to ensure that asphalt mixes meet both rutting and cracking performance criteria in a balanced manner.

For example, tests utilizing the HWT and IDEAL-CT methods on ACE XP asphalt mixes can be seen in Figures 1 & 2. The results compare mixes with and without ACE XP and show clear performance advantages with ACE XP in both rutting and cracking sample results.

Bottom line: In balanced performance testing, ACE XP Polymer Fiber yields an improvement of 30% to 50% in both rutting and cracking performance. To learn more about ACE XP or how to achieve a balanced approach to testing using the IDEAL-CT method, contact us.

Asphalt crack testing

Fig. 1 - Hamburg Wheel Tracker (HWT) Test Example:

Fig. 1 – Hamburg Wheel Tracker (HWT) Test Example


IDEAL-CT Crack Test

Fig. 2 – IDEAL-CT Crack Test Example: