SEDL / STP / STP1241-EB / STP18196S

Properties of Microwave Recycled Asphalt Cement Binders

Shoenberger, JE
Civil Engineer, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS

Rollings, RS
Research civil Engineer, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS

Graham, RT
Materials Engineering Technician, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS

Pages: 15    Published: Jan 1995

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Abstract

Recycling asphalt concrete pavements are currently limited to about 40 to 60 percent of recyclable asphalt pavement (RAP) in the mixture, with the remaining material composed of new asphalt and aggregates. The use of microwaves for heating allows the possibility of recycling with 100 percent RAP material. The effect of microwaves on asphalt cement binders was evaluated using conventional viscosity and penetration tests. The binders were also evaluated using Gel Permeation Chromatography (GPC), Fourier-Transform Infrared Spectroscopy (FTIR), and Dynamic Shear Rheometer (DSR). Viscosity and penetration testing provided opposing results with each showing slight increases in value after microwaving of the binder. A noticeable change in the molecular size distribution was observed with the GPC with the addition of a recycling agent. An increase in G^* occurred at high temperatures or low frequencies after microwaving. This increase was more pronounced on severely oxidized or hardened asphalts. The increase in G^* did not correlate well with measured viscosity and penetration values. The steady-state viscosity values obtained followed the same general trend as the results from conventional viscosity testing.