EFFECT OF ASPHALT ADDITIVES ON PAVEMENT PERFORMANCE. INTERIM REPORT

Test pavements were constructed in four districts in the mid-1980s to assess the effectiveness of asphalt additives in reducing cracking and rutting in asphalt concrete pavements. Field trials were built in Districts 1, 2, 19, and 21 and their performance has been evaluated. Ride quality of all pavements has proven approximately equivalent and satisfactory. Some pavements exhibit cracking at the surface. EVA modified and control pavements have shown the most cracking. Polyethylene, SBS, SBR, and carbon black appear capable of reducing or delaying cracking in asphalt pavements. Test pavements in District 19 were cored and the cores were tested in the laboratory. Testing consisted of recovering asphalt to measure penetration and viscosity as well as Hveem and Marshall stability, indirect tension, resilient modulus at five temperatures, moisture susceptibility, creep, and permanent deformation. Laboratory test results did not reflect the findings from the field condition surveys. Based on the findings of these tests on pavement cores, along with their comparisons to field performance and past experience with these test procedures, it appears that these test methods can identify very bad and very good mixes (regarding cracking and rutting) but cannot detect subtle differences in mixtures properties that can contribute to significant differences in cracking and rutting.