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South Dakota Department of Transportation
Project Synopsis

Title: Effects of Hot Plant Fuel Characteristics and Combustion on Asphalt Concrete Quality
Project Researcher: Rebecca McDaniel,
Project Manager: Paul Oien
Research Period: 9/27/2001 - 10/31/2003
Status: Approved
Cost: $140,000.00

Problem Statement:The South Dakota Department of Transportation spends millions of dollars each year to resurface and initially surface roads with asphalt concrete. The mix design controls most of the materials used to ensure that the asphalt concrete has long life with minimal maintenance, resistance to rutting, and resistance to fatigue cracking. The fuels used to heat the aggregates are one of the items that are not controlled by the mix design. The unknown factors that arise from fuel types and combustion efficiencies may include:
  1. residual material that can be inadvertently incorporated into the asphalt concrete from incomplete combustion;

  2. deleterious materials such as excess water, suspended solids, and high concentrations of heavy metals that can occur in any fuel, but are of extra concern in recycled motor oils.

Previous research conducted by the Oregon Department of Transportation in 1983 indicates that asphalt mixing plant design, type of dryer, dust collection system, asphalt grade and supplier, and burner fuel type can all contribute to tenderness of asphalt concrete. Other potential problems that may be linked to fuel types and combustion efficiency include cracking, stripping, rutting, and ravelling, but there is no conclusive documentation to support this.


Research Objectives:
1  Determine the effects of fuel type, fuel quality, and combustion conditions on the physical and chemical properties of asphalt concrete produced in Hot Mix Asphalt (HMA) plants.
2  Assess the potential effects of the physical and chemical properties induced by fuel type, fuel quality, and combustion conditions on field performance and constructability of asphalt concrete.
3  Recommend specifications for fuel type, fuel quality, and combustion conditions that ensure acceptable asphalt concrete performance.
4  Develop or recommend test methods that field personnel can easily use to ensure compliance with the recommended specifications.

Research Tasks:
1  Meet with the project’s technical panel to review project scope and work plan.
2  Review previous and ongoing research, conduct a survey of other states’ experience, and present findings to the technical panel.
3  Evaluate current practices used by HMA plant manufacturers to determine combustion efficiency, and recommend methods for use in tasks 4 and 5.
4  Using solvent extraction or other appropriate methods, determine the combustion residue content on aggregates heated in an operating HMA plant under conditions of insufficient, optimum, and excess oxygen. The aggregates will be heated with no asphalt
5  Using Gel Permeation Chromatography or other appropriate tests for molecular weight distribution as well as chemical testing for trace elements, test asphalt cement before it is combined with aggregates and when it is extracted from asphalt concrete
6  Evaluate asphalt concrete produced from the fuel combustion conditions of insufficient, optimum, and excess oxygen using wheel rutting tests, Tensile Shear Rheometer with freeze thaw, film thickness, Marshall stability, Marshall mix parameters, or ot
7  Evaluate asphalt cement extracted from the same sample lots to determine what affects the different fuels and combustion conditions have on ductility, viscosity, penetration, and other significant physical properties of the asphalt cement.
8  Based on analysis of test results determine what implications, with respect to pavement performance and life cycle costs, that the different fuels and combustion conditions have on asphalt concrete.
9  Develop specifications for fuels and combustion conditions that will ensure production of acceptable asphalt concrete.
10  Determine test method(s) and frequency of tests necessary for field personnel to easily determine when HMA combustion conditions are in compliance with the recommended specifications.
11  Prepare a final report and executive summary of the research methodology, findings, conclusions, and recommendations.
12  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

Documents Available:
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