AASHTO T 344:12(2020) Standard Method of Test for Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using Simulated Loading.
4 SUMMARY OF PRACTICE
4.1 The internal angle of gyration of an SGC is measured dynamically with an instrument inserted into the SGC mold.
4.2. A load (moment) is induced on the SGC while the internal angle is simultaneously measured. The simulated loading conditions are similar to those created by compaction of a standard SGC volumetric specimen.
4.3. The internal angles at each end of the mold are measured and then averaged to obtain the effective internal angle of’ gyration.
SIGNIFICANCE AND USE
SGCs are used to produce hot mix asphalt (IIMA) mixture specimens in the laboratory to assess and predict pavement performance. In the fabrication of an SGC specimen, loose IIMA is placed inside a metal mold, which is then placed into an SGC. A constant consolidation pressure is applied to the sample while the mold gyrates at a nominally constant angle (referred to as the angle of gyration) and rate. Consistency in the density of the 1-IMA specimens produced is very important to the validity of the tests performed. Specimens of a consistent density are produced when an SGC maintains a constant pressure and a known constant angle of gyration during the compaction process.
5.2. There are several manufacturers and models of SGC. liach model employs a unique method of setting, inducing, and maintaining the angle of gyration. Each model also employs a unique calibration system to measure the external angle of gyration. These existing calibration systems cannot be used universally on all of the different SGC models commercially available. Inconsistencies in HMA specimens produced on different SGC models have been attributed to variations in the angle of gyration.
5.3. This practice describes instruments and processes that can be used to independently measure the internal angle of gyration of any manufacturer’s SGC model under simulated loading conditions.AASHTO T 344 pdf download.