Views:5 Author:Site Editor Publish Time: 2020-07-27 Origin:Site
In the 1980s, the asphalt binder tester industry began to focus on the growing demand for a better understanding of the rheological properties of asphalt binders. Prior to this, basic flow characteristics were mainly measured by viscosity tests. For traditional unmodified asphalt binders, viscosity testing is well-suited for characterizing high temperature flow characteristics. At high temperatures of 60 ° C (140 ° F), the elastic component of a typical pavement-grade asphalt binder tester is almost non-existent. Therefore, the measured asphalt viscosity is directly related to its stiffness.
1.provide all the information needed to understand the rheology of asphalt binder tester
2. good basic measurements of asphalt binder tester
3. ensure the performance of asphalt binder tester materials
Viscosity testing does not provide all the information needed to understand the rheology of a typical pavement-grade asphalt binder tester at low and medium temperatures. This is true because the asphalt will change as the test temperature changes. At lower temperatures, asphalt binders are more like a resilient solid than a viscous fluid. Therefore, the elastic portion of the asphalt binder starts to become more important than the viscous portion. Because the viscosity test only tests the viscous part of the asphalt binder, it cannot fully describe the flow characteristics of the asphalt binder at low and medium temperatures.
In addition to the lack of good basic measurements at low and medium temperatures, another major factor affects the use of viscosity testing as a preferred specification property. In the 1980s, many users and manufacturers began to increasingly use modified asphalt binders to address some concerns about asphalt pavement performance. Since elastomers, such as styrene butadiene (SB), are the primary modification methodS used by many suppliers, "new" asphalt binder testers have an important elastomeric part, making viscosity testing a useful tool even at high temperatures. Its flow characteristics are not very useful.
Recognizing the need to improve testing and specifications to ensure the performance of asphalt materials, in the 1980s Congress initiated the Strategic Highway Research Program, or SHRP for short. Among other research projects, SHRP includes a five-year, $ 50 million asphalt binder tester material research project. As part of this research plan, asphalt researchers began to refine tests and specifications to better characterize the physical properties of asphalt binders over a wide range of operating temperatures. Production temperature ranges from a maximum of 135 ° C (275 ° F) to a minimum of -40 ° C (-40 ° F) winter operating temperature.
In addition, researchers need to consider the fact that aging, whether short-term aging, such as aging that occurs during construction, or long-term aging, such as aging that has been exposed to natural environments for many years, increases the stiffness of asphalt binder testers. In addition, with the demand for asphalt pavements, ie increased traffic loads and higher performance expectations, the use of modified asphalt binder tester will also increase. Recent investigations show that this is indeed the case.
In order to meet a wide range of testing needs, SHRP researchers use the asphalt binder tester as the main tool in the toolbox, and future technicians will use it to characterize the rheological properties of asphalt binders. Although it is possible to determine an asphalt binder tester that can adequately handle measurements over a wide range of temperatures and stiffness, it becomes clear that, with the choice of parallel plate geometry, torque capabilities may drive the complexity and expense of the equipment. As a compromise, the researchers chose to use a DSR with sufficient torque capability to handle mid- and high-temperature tests. Depending on the hardness of the asphalt binder, the current specification grade dsr can operate at temperatures from 0 ° C (32 ° F) to 100 ° C (212 ° F).