Balanced Asphalt Mixture Design through Specification Modification

Abstract

Traditional asphalt mixture design practices recognize the need for laboratory parameters, which relate to field performance throughout the life of the pavement. However, many design methodologies consider volumetric proportions and strength characteristics of the mixtures, which may not provide adequate insight into mixture performance. Laboratory testing that can ascertain an asphalt mixture's capability to resist common distresses is needed to complement current design methodologies. Distresses commonly associated with flexible pavement failure are fatigue cracking and permanent deformation (rutting). The Louisiana Department of Transportation and Development proposed specification modifications for 2013 to address the need for balanced mixtures (i.e., mechanistic laboratory evaluation to complement volumetric criteria). This paper presents Louisiana's experience with specification modifications to develop a balanced mixture as evaluated through the use of the Hamburg loaded wheel tester (HLWT) and semicircular bend (SCB) tests. Laboratory performance of 11 mixtures produced with the 2013 proposed specification modifications was compared with that of 40 mixtures produced under the 2006 specifications. Laboratory tests included HLWT and SCB to evaluate rutting and intermediate temperature cracking, respectively. The research showed that specification modifications did not adversely affect rutting or fatigue cracking resistance of the mixtures.

Performance Analysis of Asphalt Mixtures Modified with Ground Tire Rubber Modifiers and Recycled Materials

“…Zhou et al furthered their approach in 2013 by suggesting the inclusion of project-specific cracking requirements for asphalt mixtures [56]. Cooper et al proposed a balanced mix design method by using HWTT and Louisiana's intermediate temperature Semi-Circular Bend (SCB) test in a 2D interaction plot [57]. Buttlar et al introduced the Performance-Space diagram, an interactive plot with Hamburg rutting results in reverse arithmetic scale on the y-axis and the DC(T) fracture energy results on the x-axis [11].…”

Asphalt Mixture Quality Acceptance using the Hamburg Wheel-Tracking Test

“…The results of this study suggest the following findings. 6. Both types of QA specimens could be implemented in HWTT evaluations; however, the given advantages and disadvantages in regards to their laboratory testing ability should be considered in evaluations and analysis.…”

“…For example, the Massachusetts Department of Transportation (MassDOT) specifies a maximum rut depth of 12.5 mm at 20,000 passes combined with no SIP before 15,000 passes after all volumetric requirements have been met ( 3 ). Similarly, the Louisiana Department of Transportation and Development (LaDOTD) specifies a maximum rut depth of 10.0 mm at 20,000 passes for mixtures with unmodified binders and 6.0 mm at 20,000 passes for polymer-modified mixtures ( 6 ). The Wisconsin Department of Transportation (WisDOT) specifies that HWTTs must be conducted at 45°C and use the number of wheel passes needed to reach 12.5 mm as the rutting criterion; the number of wheel passes varies according to the mixture binder grade ( 14 ).…”

“…As QA programs are implemented to guarantee high construction standards and quality materials, SHAs are using the HWTT to increase the likelihood of obtaining mixtures that can resist rutting in the field ( 3 , 6 ). In fact, some SHAs perform the HWTT as a proof test in addition to mixture design procedures and have created databases for specifications requirements ( 7 ).…”

Evaluation of polymer modification in asphalt mixtures through digital image correlation and performance space diagrams

“…This type of plot provides the user with a graphical means to understand shifts in rutting and cracking performance caused by changes in mixture ingredients, mixture composition and/or mixture volumetrics. Zhou et al (2013) and Cooper III et al (2014) used this concept to evaluate recycled asphalt sources, binder grades, etc. in terms of rutting and fatigue or reflective cracking.…”