THE EFFECT OF ANTISTRIP TREATMENTS ON ASPHALT-AGGREGATE SYSTEMS - AN ENVIRONMENTAL SCANNING ELECTRON-MICROSCOPE STUDY

The performance of three antistrip additives-a lime-treated aggregate, an amine-treated asphalt and a styrene-butadiene rubber-treated aggre gate, was studied with an environmental scanning electron microscope ( ESEM). Samples were prepared with the untreated asphalt and aggregate, the treated asphalt with untreated aggregate and untreated asphalt wi th each treated aggregate. The same asphalt and aggregate sources were used in each test and all samples were run in duplicate. All samples were examined along the asphalt-aggregate interface in the ESEM prior to and following each freeze-thaw cycle. The samples were subjected to a total of ten freeze-thaw cycles. All three additives reduced the po tential for moisture damage by maintaining asphalt-aggregate adhesion better than the control samples. Based on ESEM observation of the asph alt-aggregate interface before and after freeze-thaw cycling, the styr ene-butadiene rubber-coated aggregate samples performed better than th e amine-treated asphalt samples which performed better than the lime-t reated aggregate samples.