Laboratory Evaluation of Sulfur-Modified Warm Mix

As asphalt prices have continued to escalate over the past few years, a great deal of interest has been focused on using more Reclaimed Asphalt Pavement (RAP) or finding a material that can replace a portion of the asphalt binder in asphalt concrete (AC) mixtures. Hot liquid sulfur was used as an extender of asphalt binder in hot-mix asphalt (HMA) in the 1970s and the early 1980s. However, a sharp increase in the sulfur price, significant generation of fumes and odors, and the problematic transportation and introduction of hot liquid sulfur into the HMA brought its utilization in road paving to an end by the late 1980s. To overcome these obstacles, a solid sulfur pellet technology, known as Shell Thiopave5, was developed. The sulfur pellet is an asphalt mixture modifier that also extends the asphalt binder. The technology also contains other additives beyond elemental sulfur designed to lower the mixing temperature as a warm-mix asphalt (WMA) mixture and to reduce odors and fumes during production. This paper details a comprehensive laboratory evaluation of a control mix and sulfur-modified asphalt mixtures with varying binder replacement levels. Laboratory performance tests were conducted to measure the resistance of these mixes to moisture damage, permanent deformation, fatigue cracking, and low-temperature cracking. The results of the study showed that the sulfur-modification resulted in a tangible increase in stiffness over the control mixture when tested for dynamic modulus. This increase in stiffness afforded these mixes superior rut resistance versus the control mix in the Asphalt Pavement Analyzer, Hamburg Wheel-Track Device, and Asphalt Mix Performance Tester (AMPT). However, moisture susceptibility testing, both by the determination of a tensile strength ratio (TSR) and Hamburg testing, showed increased moisture susceptibility for these sulfur-modified mixes. The addition of the sulfur modifier also influenced the estimated endurance fatigue limit (EFL) of those mixtures. Compared to the control mix, one sulfur modified mix exhibited a higher estimated EFL, one mix showed an equivalent EFL, and two mixes had lower EFL. Finally, the low-temperature cracking resistance of the asphalt mix was not significantly affected by the presence of sulfur modification.

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  • Authors:
    • Taylor, Adam Joel
    • Tran, Nam H
    • May, Richard
    • Timm, David H
    • Robbins, Mary M
    • Powell, Buzz
  • Conference:
  • Publication Date: 2010

Language

  • English

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  • Accession Number: 01328010
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 20 2011 11:22AM