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EFFECT OF MICROWAVE ENERGY ON THE PROPERTIES OF ASPHALT AND ITS USE AS AN AGING TOOL.
| 题名： | EFFECT OF MICROWAVE ENERGY ON THE PROPERTIES OF ASPHALT AND ITS USE AS AN AGING TOOL. |
| 作者： | Bishara-SW; McReynolds-RL |
| 关键词： | ASPHALTS-; ACCELERATED-AGING; MICROWAVE-RADIATION; DIELECTRIC-CONSTANT; DISPERSITIVITY-; MOLECULAR-SIZE-INDEX; HIGH-PERFORMANCE-SIZE-EXCLUSION-CHROMATOGRAPHY; ACCURACY-; TIME-SAVING-METHODS |
| 摘要： | Microwave energy causes changes in asphalt properties. Unsymmetric organic molecules with dipoles, that is, with a permanent separation of positive and negative charges, undergo excitational rotation when they are subjected to microwave radiation. The excitational rotation depends on the material's dielectric constant. Because the radiation frequency is relatively high and the dielectric constant of asphalt is low, asphalt molecules cannot rotate as fast as the applied electromagnetic field, and an out-of-phase component of the dielectric constant, called dielectric loss, is dissipated as heat. Treatment of asphalt for a short time with low-power microwave radiation decreases the dispersitivity (D) and molecular size index (MSI) values obtained by high-performance size exclusion chromatography (HPSEC). Alternately, exposure for a longer time to a higher-power radiation increased both the D and MSI values for 12 asphalts studied. Microwave conditions (power level, treatment time, sample weight, and sample container material) were tailored to simulate the effects obtained after rolling thin film oven-pressure aging vessel (RTFO-PAV) aging of 18 asphalts. HPSEC gave comparable results for the two aging techniques: RTFO-PAV aging versus microwave aging. The difference in MSI amounted to +/-7.3 and +/-4.2 percent by using gravimetry and ultraviolet detection at 345 nm, respectively. The bending beam rheometer showed that microwave energy underestimates aging by a maximum of about 3 deg C in the limiting low temperature. Accelerated aging by microwave radiation is very simple and consumes less than 3 hr. |
| 总页数： | Transportation Research Record. 1995. (1488) pp1-12 (4 Fig., 9 Tab., 17 Ref.) |
| 报告类型： | 科技报告 |
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