Improved methods for extracting and recovering asphalts from pavement samples /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
|
| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Two new procedures for the purpose of extracting asphalt binder from hot-mix and pavement samples have been developed. Flaws in previous methods include: 1) the inability to completely remove solvent from recovered asphalt, 2) the inability to completely extract asphalt from the aggregate, and 3) a tendency to alter asphalt properties during extraction. The new methods improve precision and accuracy by minimizing these errors. The new procedures also conserve solvent and require less operator effort. As specified, the standard ASTM solvent removal procedure is not capable of removing all of the extraction solvent from extracted asphalts. Analysis of residual solvent by Gel Permeation Chromatography (GPC) made it possible to determine optimal conditions for solvent recovery such as oil bath temperature, nitrogen flow, vacuum, and recovery time. Both the Abson and Roto-vap methods were studied. Neither provided consistent solvent removal for varying grades of asphalts. After raising recovery temperatures and extending recovery times, both methods were capable of removing all solvent from asphalts having 60°C viscosities of 200,000 poise. During extraction, asphalts are dissolved in strong solvents for several hours. ASTM D-2172B subjects asphalts to dilute solutions of trichloroethylene (TCE) at 80°C for several hours. Exposure to solvents causes hardening and softening of asphalts depending on the concentration and temperature. Solution conditions which result in minimal hardening or softening were determined. The new methods were designed such that asphalts are not exposed to hash solution conditions. Previous methods left up to 10% of the asphalt on the aggregate. This was due to poor mixing and the use of weak solvents. Several solvents were studied for their ability to extract strongly adsorbed material from aggregate fines. TCE with 15% ethanol (TCE/EtOH) and toluene with 15% ethanol (Tol/EtOH) showed good extractibility and were chosen as the extraction solvents for the new methods. The new methods also incorporated continuous mixing of the solvent-aggregate-asphalt slurry... |
|---|---|
| Item Description: | Vita. "Major subject: Chemical Engineering." |
| Physical Description: | xx, 211 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |