A Manual for Design of Hot-Mix Asphalt with Commentary (2011) / Chapter Skim
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Pages 15-27
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From page 15... ...
Specifications for asphalt binders must control properties at high, low, and intermediate temperatures. Furthermore, test methods used to specify asphalt binders usually must be conducted with very careful temperature control; otherwise, the results will not be reliable.
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From page 16... ...
The shortcomings in both older empirical tests and in the newer viscosity tests eventually led to the development of a more effective system 16 A Manual for Design of Hot Mix Asphalt with Commentary 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 -40 -20 0 20 40 60 80 Temperature, oC M od ul us , P a Modulus at -30 oC is 37,000 times the modulus at 50 oC Figure 3-1. Change in dynamic shear modulus with temperature for typical asphalt binder (frequency = 10 rad/s)
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From page 17... ...
Performance Grading -- Test Methods Most of the tests used in performance grading of asphalt binders involve rheological tests. Rheology is the study of the way materials flow, so a rheological test is one that measures one or more aspects of the way in which a material flows.
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From page 18... ...
This is followed by a discussion of the grading procedure and a section covering practical aspects of performance grade selection for HMA mix design. 18 A Manual for Design of Hot Mix Asphalt with Commentary Unaged binder DSR test at high temperature RTFOT aging & mass loss determination DSR test at intermediate temperature PAV aging BBR test at low temperature Direct tension test at low temperature (optional)
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From page 19... ...
DSR Test at High Temperature The primary purpose of the DSR test at high temperature is to ensure that a properly specified asphalt binder will have the proper engineering properties at high temperature and, when used in an HMA mix, will keep it from rutting and shoving under traffic. The DSR is a torsional test in which a thin specimen of asphalt binder is sheared between two circular plates.
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From page 20... ...
For example, one of the most common grades of asphalt binder is PG 64-22; the high-temperature DSR test on this binder would be performed at 64°C. The DSR test measures both modulus and phase angle.
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From page 21... ...
The DSR test at intermediate temperatures is designed to prevent binders from becoming too stiff at intermediate temperatures, which can contribute to premature fatigue cracking in pavements. This also helps to control the overall flow properties of the asphalt binder.
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From page 22... ...
Performance Grading -- Specification Table 3-1 lists the various requirements for performance-graded asphalt binders, as described in AASHTO M 320 Table 1. In AASHTO M 320 Table 1, the low-temperature grade of the binder is based on creep stiffness and the m-value of the binder from the BBR.
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From page 23... ...
Specification for performance-graded asphalt binders. (continued on next page)
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From page 24... ...
In this case, the low pavement temperature is defined simply as the minimum pavement temperature at the pavement 24 A Manual for Design of Hot Mix Asphalt with Commentary PG 76 PG 82 Binder Performance Grade: −10 −16 −22 −28 −34 −10 −16 −22 −28 −34 Design high pavement temperature, °C: <76 <82 Design low pavement temperature, °C: ≥10 ≥16 ≥22 ≥28 ≥34 ≥10 ≥16 ≥22 ≥28 ≥34 Tests on Original Binder Flash Point Temperature (T 48) , Min., °C 230 Viscosity (T 316)
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From page 25... ...
In the example illustrated in this plot, at a 65% reliability level, the design high pavement temperature is 54.7°C, and the design low pavement temperature is 7.1°C. Calculation of design high and low pavement temperatures at different reliability levels involves compilation of a wide range of weather data and analysis of this data to produce both average values and standard deviations for design high and low pavement temperatures for thousands of sites throughout the United States and Canada.
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From page 26... ...
Additional details concerning the selection of asphalt binders for HMA mixtures are given in Chapter 8 of this manual. Bibliography AASHTO Standards M 320, Performance-Graded Asphalt Binder M 323, Superpave Volumetric Mix Design PP 42, Determination of Low-Temperature Performance Grade (PG)
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From page 27... ...
T 316, Viscosity Determination of Asphalt Binder Using Rotational Viscometer Other Publications The Asphalt Institute, Asphalt Binder Test Manual (MS-25)
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