As the asphalt industry moves toward balance/performance mix design testing, one of the primary testing methods for cracking that is being reviewed is ASTM D8225 – Determination of Cracking Tolerance Index of Asphalt Mixture Using the Indirect Tensile Crack Test at Intermediate Temperature (commonly known as Ideal-CT). Currently, the primary piece of equipment used for this test is the Pine 850T Test Press. This unit is already owned by most producers in Virginia, so it’s the natural choice for testing.
Recently Pine Test Equipment, Inc. issued a letter informing clients that the Pine 850T Test Press did not meet the constant deformation rate of 50 ± 2.0 mm/min required for ASTM D8225. In layman’s terms during a test, the deformation starts at 50 mm/min, but just before the specimen breaks, when there is maximum resistance, the deformation may drop below acceptable limits; then, after the break, there may be a slight increase.
Since then, research engineer Fujie Zhou from Texas A&M Transportation Institute (TTI) has done some work comparing a Servo-Hydraulic Machine (Testquip) with the Pine Press, which has a screw mechanism. This work has shown that there is no statistically significant difference between the two machines. There has even been some discussion about changing the tolerance of 50 ± 2.0 mm/min required for ASTM D8225.
Continue to follow VAA for future developments on this topic.