[MUSIC] Hello, this is JP, Jean Pascal Planche again. It's a pleasure to meet you for this new technical session. This is a real pleasure for me to share some information about the use of specific test methods to assess the rheology of bitumens. The purpose of this video session is to become familiar with the bending beam rheometers, BBR, and dynamic shear rheometers, DSR and to learn how they use in different test. We will also detail the meaning of performance grades and how they are obtained from testing. Lastly, we will explore the multiple stress creep and recovery test, MSCRT, and its purpose. We will review the differences between Bending Beam Rheometers and Dynamic Shear Rheometers and which test they are used for based on the data they produce. Then we will go briefly over the supervised Performance Grading procedure and meaning in use in North America. Finally, we will explore the MSCR test and its applications in bitumen rheology. Bending beam rheometer does what is sounds like. It bends a beam. In this case the beam is being bent and made by pouring hot bitumen in a rectangular mold. The BTM beam is immersed in the DSR apparatus, in a recirculating fluid bath to control the temperature. The beam is supported at each end as the BBR piston presses down on the center of the beam. The BBR works by applying a specific load to a center of a bitumen beam, the resulting deflection of the beam over time is measured by the BBR. The deflection data is mathematically converted to a relaxation curve of creep stiffness over time. The stiffness S and the slope m of the stiffness over time are calculated parameters using the superpave specifications. But you need a data point at 60 seconds loading time. This test typically is conducted at a temperature below zero degrees C. In a dynamic shear rheometer, the bitumen sample is sandwiched between two parallel circular plates and trained so no excess of bitumen is flowing out of the sides. One of the plates is held in place and the other rotates back and forth in controlled oscillations. The DSR measures the resistance of the bitumen during the oscillations. There are two ways that DSRs are built to do this. Stress-controlled DSRs apply a a known amount of torque and measure the resulting displacement of the bitumen. Strain controlled DSR apply a known displacement and measure how much torque is generated. In the DSR, the bitumen is oscillated several times at each frequency for each temperature isotherm. Typically the complex modules G* and phase angle data, among other data, are calculated and recorded. Master curves can also be generated by combining the isotherms, as explained in another video. A performance grade PG, is a set of two numbers Indicating the upper and the lower service temperature limits. In the original version of the super specifications, the PG represents the seven-day maximum/minimum pavement, not air, temperature allowable. For example, and as for we need PG 58 minus 28 may be used in climates where the asphalt surface temperatures are between 58 degrees C and minus 28 degrees C. To get the lower PG of bitumen, the BBR is used. The stiffness on m values are measured after 60 seconds at 10 degrees above the lower service temperature. S must be below 300 mega-pascal, and m must be above 0.3 for the sample to pass. To get the upper PG of a bitumen a DSI equipped with 25 mm diameter plates is used. G* and delta are measured at 10 radians per second at the upper service temperature. G* over sine delta must be greater than 1 kilopascal for neat bitumens or 2.2 for RTFO-aged bitumens. There is another specification criterion at intermediate temperature that will be further detailed in another video. The MSCR test was designed to try to predict the rutting severity of bitumens. It consists of a series of repeated creep tests followed by recovery time. It is performed using a DSR with 25mm plates; a load is applied to the sample for one second. After one second, the load is removed and the sample is allowed to relax back towards its original position for nine seconds. This is repeated 10 times at 2 strain levels. The average percent recovery and non-recoverable compliance are calculated for both strain levels and compared. The MSCR test can better distinguish between bitumens with and without polymer modification. particulary by combining the percent recovery and the creep compliance. It has been recently adopted for specifications for a new test method for assessing the upper PG limit. It is then run at the upper temperature of a PG grade based on local climatic conditions. This will be detailed further in another video as well. Notice that these test methods is now standardized in Europe and another reference EN166 59. In conclusion, we get to know how the BBR works and the creep stiffness data ice produces. We also looked at two types of DSRs and some frequency sweep data that they are typically used to obtain. Then we learned what a PG actually means, and explored how the data from these rheometers are used to determine PGs. Finally, we broke down what occurs during the MSCR test and that it ultimately attempts to predict rutting performance. I thank you for watching and enjoy the rest of this MOOC. [MUSIC]