2013 Session: 670

• Influence of Aggregate Packing and Asphalt Binder Characteristics on Performance of Stone Matrix Asphalt
  Abstract: Stone matrix asphalt (SMA) is valued for its high resistance to rutting and durability characteristics. These characteristics of SMA mixtures are mainly the result of the rich asphalt mastic and the good stone-on-stone contact provided by its coarse, gap-graded aggregate structure. SMA has been used in Virginia since 1995 with overall excellent performance. However, with the introduction of the 9.5 mm SMA mix in 2003, the field performance of this mix has been variable. This paper focuses on the laboratory evaluation of asphalt binder and aggregate packing effects on the rutting resistance of SMA, the primary failure mechanism for the SMA-9.5. The objective was to identify defining characteristics of SMA mixtures that impact field performance. Four SMA-9.5 mixtures with known field performance – two good performers, one marginal performer, and one poor performer - were reproduced in the laboratory and tested. Rutting resistance of the mixtures was evaluated using the flow number (FN) obtained from repeated load permanent deformation tests and the asphalt pavement analyzer. In addition, dynamic shear rheometer, bending beam rheometer, and dynamic modulus testing were conducted to characterize the asphalt binder and mixtures stiffness. The results indicated that rutting resistance of SMA was dependent on binder stiffness, binder content, and aggregate structure (gradation, VCA, and Abrams fineness modulus). Mixtures with history of good field performance showed significantly higher FN than the poor performers. Both binder content and aggregate packing (fineness modulus and VCAmix) were lower for the good performing mixtures but binder content appears to have more significant influence on FN – a one percentage point increase over VDOT minimum binder content of 6.3 percent resultant in significant decrease in rutting resistance irrespective of aggregate packing characteristics. It was concluded that combination of traffic characteristics (slow-moving, turning, or stopped), aggregate packing (higher VCAmix, lower Abrams modulus, higher percent passing No. 4 sieve), and binder amount, may have contributed to the observed poor SMA field performance.
  Authors: Apeagyei, Alex K.; McGhee, Kevin Kenneth; Clark, Trenton
  Authors: Apeagyei, Alex K.; McGhee, Kevin Kenneth; Clark, Trenton
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 670
  Paper Number: 13-0622
• Significance of Mixture Parameters on Binder Aging in Hot-Mix Asphalt Mixtures
  Abstract: Traditionally, aging studies of asphalt materials have been conducted primarily on asphalt binders only, omitting any potential influence by the aggregate. These results are commonly extrapolated to the mixture behavior without a comprehensive understanding of how the mixture characteristics may potentially influence the aging of the binder within the mixture. This study was initiated by the FHWA to evaluate the effects of mixture parameters, namely different aggregate and asphalt binder sources, air voids, and binder contents on the aging characteristics of asphalt binders aged in mixtures. Those same binders were also aged in pressure aging vessel (PAV) pans in laboratory ovens to determine the aging characteristics of the asphalt binders, as is the current state of practice. These characteristics were determined by the binder kinetics, in terms of the carbonyl area (CA) measured from the Fourier Transform Infrared Spectroscopy spectra as a function of aging time and temperature. The hardening susceptibility (HS) of the asphalt binders as defined by the relationship between the low shear viscosity (LSV) and the carbonyl area was also determined. The HS relationships of the asphalt binders aged in the mixtures were compared to the HS of the binders aged in the PAV pans and were found to be statistically dissimilar for some mixtures and statistically similar for others. The analysis revealed that the effective binder content (Pbe) of the mixtures provided the strongest indicator as to whether or not the evaluated mixture parameters would have a significant influence on the aging characteristics of the asphalt binder.
  Authors: Morian, Nathan; Hajj, Elie Y; Sebaaly, Peter E.
  Authors: Morian, Nathan; Hajj, Elie Y; Sebaaly, Peter E.
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 670
  Paper Number: 13-2070
• Evaluation of Semiflexible Composite Mixture Using Indirect Tensile Tests
  Abstract: The main purpose of this paper was to evaluate the engineering properties of Semi-Flexible Composite Mixture (SFCM). A slab SFCM sample was fabricated in the laboratory to simulate the filling of cement mortar in the field. Performance testing was carried out by Indirect Tensile (IDT) mode and using Material Testing System (MTS) equipment. IDT testing has been found to be able to correlate with the field performance of asphalt mixtures at low, intermediate, and high temperatures. They were thus used in this study to evaluate the thermal cracking, fatigue, rutting, as well as moisture resistance of SFCM. A control hot mix asphalt (HMA) mixture was used to compare with the results of SFCM. Based on the testing results, it was found that the designed SFCM showed good filling capability of cement mortar. SFCM had higher dynamic modulus than the control HMA. It had good resistance to rutting and moisture damage. Based on fracture work, SFCM showed better resistance to thermal cracking while lower resistance to fatigue cracking.
  Authors: Zhang, Weiguang; Shen, Shihui; Huang, Hai; Goodwin, Ryan D.
  Authors: Zhang, Weiguang; Shen, Shihui; Huang, Hai; Goodwin, Ryan D.
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 670
  Paper Number: 13-4304
• Effectiveness of Antistrip Agents in Asphalt Mixtures
  Abstract: Since the late 1970s there has been much research performed to better understand the stripping phenomenon in asphalt mixtures. As a result, there have been changes in both materials and technology over the past 30 years to improve the resistance to moisture damage and the ability to test for performance under adverse moisture conditions. Due to the changes in materials and technologies related to the development and improvement of anti-strip agents, this research study was conducted to evaluate the effectiveness of current anti-strip agents used in hot mix asphalt pavements.The objectives of this project was to construct a field test section that used three different anti-strip agents in a conventional Superpave surface mixture, and conduct a series of laboratory performance test comparisons using different aging periods to make long-term comparisons of the effectiveness of hydrated lime, liquid additive, and Warm mix antistrip additives.Some of the pertinent conclusions from this research study are summarized as follows: - Multiple freeze/thaw cycles of 0, 1, 5, and 10 cycles were used for a portion of the research study. Hydrated lime had the highest tensile strength and highest TSR values and was the only additive treatment to meet the minimum of 80% TSR for all freeze/thaw cycle combinations. - Both 5 and 10 freeze/thaw cycles were significantly more discriminating in regard to moisture susceptibility than one freeze/thaw cycle alone. - WMX treated mixtures produced low initial tensile strengths, but the strength of these mixtures improved with time.
  Authors: Watson, Donald E.; Moore, Jason Roox; Taylor, Adam Joel; Wu, Peter Y.
  Authors: Watson, Donald E.; Moore, Jason Roox; Taylor, Adam Joel; Wu, Peter Y.
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 670
  Paper Number: 13-5061
• Influence of Aggregate Packing and Asphalt Binder Characteristics on Performance of Stone Matrix Asphalt
  Authors: Apeagyei, Alex
  Authors: Apeagyei, Alex
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 670
  Paper Number: 13-0622
• Significance of Mixture Parameters on Binder Aging in Hot-Mix Asphalt Mixtures
  Authors: Morian, Nathan
  Authors: Morian, Nathan
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 670
  Paper Number: 13-2070
• Evaluation of Semiflexible Composite Mixture Using Indirect Tensile Tests
  Authors: Shen, Shihui
  Authors: Shen, Shihui
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 670
  Paper Number: 13-4304
• Effectiveness of Antistrip Agents in Asphalt Mixtures
  Authors: Watson, Donald
  Authors: Watson, Donald
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 670
  Paper Number: 13-5061