AASHTO TP 123:2016 Standard Method of Test for Measuring Asphalt Binder Yield Energy and Elastic Recovery Using the Dynamic Shear Rheometer.
Definitions of terms used in this practice may be found in Terminology D8, determined from common English usage, or combinations of both.
The binder is prepared either at an unaged condition or using T 240 (RTFOT) to represent short- term aging of asphalt pavements, or further conditioned using R 28 (PAV) to simulate long-term aging of asphalt pavements. The sample is prepared consistent with T 315 (DSR) using the 8-mm parallel plate geometry with a 2-mm gap setting.
4.2. For the binder yield energy procedure the sample is tested in monotonic shear using a constant strain rate. The sample is continuously loaded until peak shear strength is achieved and the sample has yielded. The results can also be used to estimate ductility or forced ductility using the strain and stress at the peak of the yield curve.
4.3. For measuring the binder Elastic Recovery, after 2 minutes of monotonic shear using a constant strain rate, the sample is allowed to recover for 30 minutes before calculating the percent strain recovery.
This method is intended to evaluate the performance of binders at intermediate temperatures in terms of resistance to yielding and in terms of elastic recovery. The “yield energy” of the sample can be used to identify the relative performance of diflerent materials in terms of resistance to fatigue or extreme loading damage.
5.2. This method also provides a simple and more repeatable alternative to conducting the ductility test (T 51) and elastic recovery test (ASTM D6084), using a standard Dynamic Shear Rheometer and a small sample size. The stress-strain response curve from the yield test, as well as the strain recovery from the elastic recovery test, can be useful in identifying the presence of modifiers in binders and their potential benefits in improving ductile behavior of binders.
Note I It is to be noted that the relationship between ductility and elastic recovery to pavement performance is not known and there is no clear evidence that having higher ductility or higher elastic recovery improves pavement performance. The significance of this test is to replace the use of a ductilometer used for ductility, forced ductility, and elastic recovery with simpler and more repeatable tests in the DSR.
Condition the asphalt binder in accordance with T 240 (RTFOT) for short-term performance. or follow with R 28 (PAV) for long-term performance.
6.2. Sample Preparation—The sample for the test is prepared following T 315 for 8-mm plates. The temperature control also follows the T 315 requirements. This test may be performed on the same sample that was previously used to determine the rheological properties in the DSR on PAV residue as specified in M 320.
6.3. Test Protocol—Two variations of the BYET test protocols are hereby described: Method A describes the procedure for measuring the binder yield energy, and a surrogate test procedure for the conventional ductility Lest (T 51). Method B describes the Elastic Recovery test (ASTM D6084).AASHTO TP 123 pdf download.