The National Academies Press

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From page 5... ... The traditional equiviscous principle used to determine mixing and compaction temperatures was developed using unmodified binders having Newtonian behavior. However, using this method with many modified asphalt binders often results in excessively high mixing temperatures that have caused concerns with emission problems and degradation of the binder's properties. Read the entire page →
From page 6... ... Experimental factors included compaction temperature and the test temperature for measuring Marshall stability. A variety of types and grades of asphalt binders was incorporated in the mixes. Read the entire page →
From page 7... ... over a wide range of compaction temperatures and found that except for strain-controlled fatigue testing using a Superpave shear tester, the shear properties of the mixture improved with increasing compaction temperature. The strain-controlled fatigue results were not significantly affected by mixing temperature. Read the entire page →
From page 8... ... The discussion touched on topics such as oven aging procedures, recovery procedures, temperature control charts, and penalties. Of interest for this research was how Michigan dealt with temperature control at plants. Read the entire page →
From page 9... ... Mixing and Compaction Temperatures for Modified Asphalt Binders The use of polymer-modified asphalt binders has become much more common over the past two decades. Many types of polymers have been used in paving asphalts to enhance the performance of asphalt pavements in a wide range of climates and loading conditions. Read the entire page →
From page 10... ... The survey questions, along with a summary of responses, are as follows: 1. What procedure does your agency/organization currently use to determine mixing and compaction temperature for asphalt binders used in unmodified hot-mix asphalt? Read the entire page →
From page 11... ... 3. What procedure does your agency/organization currently use to determine mixing and compaction temperatures for asphalt binders used in crumb rubber-modified hotmix asphalt? Read the entire page →
From page 12... ... If so, what procedure is currently used to determine mixing and compaction temperatures for asphalt binders used in hot-mix asphalt modified in this manner? Fifty-nine percent of the agencies responded that they do not have experience with or do not allow air-blown or chemically modified asphalt (Figure 4) Read the entire page →
From page 13... ... and recommended its use for determining mixing and compaction temperatures for modified asphalt binders. They reasoned that since the vertical compression rate during most of the SGC compaction process is very low, the measurement of the viscosity for the binder should be made at a very low shear rate. Read the entire page →
From page 14... ... Steady Shear Flow Reinke (45) presented another concept, which he called the steady shear flow test, to determine mixing and compaction temperatures. Read the entire page →
From page 15... ... (46) evaluated eight polymer additives used to modify an AC-20 asphalt binder using a technique referred to as "Pseudo Extensional Viscosity, ηext." ηext is defined as the difference in the viscosity measured using the Rotational Viscometer for the smaller 27 spindle and the viscosity measured using the larger 21 spindle. Read the entire page →
From page 16... ... Shear Rates During Mixing and Compaction If viscosity is the binder parameter used to establish mixing and compaction temperatures, the shear rate(s) used to determine the viscosity should approximate the shear rates that occur during mixing and compaction. Read the entire page →
From page 17... ... The low shear viscosities are plotted versus temperature and mixing and compaction temperature ranges are determined at target values of 3.0 Pa·s and 6.0 Pa·s, respectively. • Takes into account the shear rate dependency of modified asphalt binders • Testing is simple to conduct • Results in lower mixing and compaction temperatures for modified asphalt binders • May not accurately represent the shear thinning behavior of modified asphalt binders • Requires extrapolation of results to a low shear rate • Cross-Williams regression model is complicated • No clear agreement on definition of zero shear viscosity • Results for some binders yield unrealistically low mixing and compaction temperatures Table 3. Read the entire page →
From page 18... ... Bucket mixer KOL M-60 65 5.6 961 96,100 Pugmill mixer 7590-H 128 3.9 1341 134,100 Workability device Instrotek 20 6.0 319 31,919 Bowl mixer Hobart A200 48 4.0 425 42,558 Rotational viscometer Brookfield DV-II+ 20 8.4 mm 17.5 6.8 Dynamic Shear Rheometer 10rad/s 25 mm 8 mm 125 20 Table 4. Summary of shear rates for some field and lab equipment. Read the entire page →
From page 19... ... 19. Research has yet to clearly identify a reliable method of determining mixing and compaction temperatures for modified and unmodified asphalt binders. Read the entire page →

From page 5...

... The traditional equiviscous principle used to determine mixing and compaction temperatures was developed using unmodified binders having Newtonian behavior. However, using this method with many modified asphalt binders often results in excessively high mixing temperatures that have caused concerns with emission problems and degradation of the binder's properties.