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Research Projects
Performance Characteristics of Rubberized Foamed Asphalt Mixtures Using Half-Warm Aggregates

Over the last few years as environmental criteria becoming stricter and stricter, new technologies have been introduced in the asphalt industry in United States that allow producing asphalt mixtures at moderated mixing temperatures commonly referred to as warm mix asphalt (WMA) or half-warm mix asphalt (HWMA).

Phase I

An experimental program was undertaken to investigate the moisture susceptibility, rutting sensitivity and fatigue resistance of laboratory made half warm mix asphalt (HWMA) mixtures containing moist aggregates using recycled materials such as manufactured roofing shingles and reclaimed asphalt pavement (RAP). The test properties evaluated in this study included indirect tensile strength (ITS), tensile strength ratio (TSR), wet flow, wet toughness, percent toughness loss (PTL), rut depth of dry and wet conditioned specimens, rut index and beam fatigue life. The following variables were evaluated for Phase I of the research project using control HWMA mixtures containing half warm aggregates.

  1. Three aggregate sources (Aggregate A Crushed Granitic Gneiss, Aggregate B Crushed Schist, and Aggregate C Crushed Granite)
  2. Three fractioned RAP sources, 15% RAP was used in this study for the selected aggregate source
  3. One recycled shingles source, 5% roofing shingles by weight of aggregate was used in this study
  4. Three hydrated lime contents (0%, 1% and 2% by weight of aggregate)

Phase I Publication

Phase II

The second phase of the experimental study was undertaken to investigate the influence of compaction temperatures on the performance characteristics of rubberized foamed asphalt mixtures using half-warm aggregates. The performance properties evaluated from the study included dynamic modulus, phase angle, E* Ratio, moisture sensitivity, and rutting resistance of HWMA mixtures using modified binders. The following variables were evaluated for Phase II of the project using HWMA mixtures containing half warm aggregates.

  1. Three binder types: regular (PG 64-22), laboratory blended (LB) rubberized binder (PG 64-22+10% CR (No. 40 mesh)) and terminal blended (TB) polymerized binder
  2. Two aggregate sources (Aggregate B Schist and Aggregate C Granite)
  3. Four compaction temperatures (203F, 185F, 158F, and 140F)

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