AASHTO M320 PDF
AASHTO Designation: M Release: Group 3 (August ). American Association of State Highway and Transportation Officials North Capitol Street. Find the most up-to-date version of AASHTO M at Engineering AASHTO M Standard Specification for Performance-Graded Asphalt Binder. standard by American Association of State and Highway Transportation.
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From laboratory tests performed on asphalt binder mixtures, m-value has been shown to be related to thermal fracture as well as thermal fatigue cracking. Effective specifications require that standard test methods are available to measure the required physical properties of asphalt binders.
ASTM Standards for Asphalt Binders
Two test methods and a calculation practice were developed for use in the Superpave specification to address low-temperature cracking performance of pavements: Why Are the New Standards Needed?
He has published numerous papers on material testing and specification. According to the specification, an asphalt binder will perform adequately at a given low service temperature if its S value is less than or equal to MPa and the m-value is greater than or equal to 0. If the creep stiffness is between and MPa, the direct tension failure strain requirement can be used in lieu of the creep stiffness requirement.
Refining Superpave asphalt binder characterization | Asphalt magazine
Asphalt binder grades may be selected by following the procedures described in M and R If the creep stiffness is below MPa, the aashyo tension test is not required. Then the data is exported to a spreadsheet and the viscoelastic continuum damage VECD approach is used to calculate the fatigue resistance of the binder the serious mechanics and calculation part. One of the new procedures being considered to characterize fatigue cracking performance of asphalt binders is the Linear Amplitude Sweep LAS test.
Conclusion The introduction of the Superpave asphalt binder system was a major step forward in characterizing the behavior of asphalts. It is a relatively fast test, but it has some serious mechanics and calculations backing it up. In the United States, the new standards are used in federal, state, city and local government laboratories involved in construction and n320 of asphalt pavements. Cutback Asphalts are commonly used in cold mixes or as prime applications.
The LAS test is performed on aged asphalt binder at an appropriate intermediate temperature using a frequency sweep test to generate rheological properties and a stepped shear strain amplitude test to generate accumulated damage in the asphalt binder sample.
Inthe U. These evaluations were performed on several types of mixes using a number of evaluation means, including loaded wheel test devices, accelerated load testers and actual pavement sites.
D is the result of the development of a comprehensive mechanistic model that enables better prediction of the performance of asphalt binders at low temperatures. Testing at additional temperatures for T may be necessary if MPa is not bracketed at the initial two test temperatures.
The DT test method as initially proposed at the end of SHRP was found to be inadequate as a standard test method due to persistent problems with various aspects of the test system. For these cases, binders with a higher temperature grade would be selected.
Refining Superpave asphalt binder characterization
M20 the Koch survey referred to above, it was found that 40 of the 51 transportation agencies have determined that the quality of asphalt binders has improved as a result of using the new test methods specified in the AASHTO M and MP1a specifications.
They fall into four categories: Thermal or low temperature cracking of the road surface leads to poor performance due to the loss of structural integrity and, ultimately, premature deterioration of the entire pavement section.
The principle aashro between AASHTO M and MP1a is that MP1a incorporates a mechanistically based criterion to define low temperature performance of asphalt binders, whereas M uses empirical parameters related to performance. This property provides an indication of the delayed elastic response of the binder.
Emulsified Asphalts are typically used as surface treatments and tack coats. The slope of log-log plot of stiffness versus time, called the m-value, is used to control the shape of the stiffness master curve of the asphalt aahsto at low temperature.
Table 2 incorporates PP42 for determining the critical low cracking temperature using a combination of T and T test procedures. Depending k320 the type, several combinations of tests can be required to verify adherence to specification. The use of polymer-modified asphalts to reduce pavement rutting has grown steadily since the late s. These properties are determined at two test temperatures as specified in the practice. This shrinkage causes thermal stresses and aasgto these stresses exceed the tensile strength of the mixture, a low temperature crack forms.
The asphalt binder shall be at least For example, an air bearing had to be used because metal bearings used in the previous design had introduced errors. Numerous evaluations of the MSCR test have shown that it is able to measure the difference in rutting potential of various modified and unmodified asphalt binders.
Sang-Soo Kim, simulates thermal cracking and allows the determination of a cracking temperature. xashto
Low temperature rheological and failure characteristics of asphalt binders may be obtained using D DT test method at other test conditions such as different strain rates, stress control tests and low temperature fatigue. The development of sound ASTM standards, such as those described in this article, is the key to measuring repeatable and reproducible fundamental engineering properties at low service temperatures.
For neat binders, a Jnr of 4.