Evaluating the Effects of the Wet and Dry Processes for Including Crumb Rubber Modifier in Hot Mix Asphalt.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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The conventional method of modifying an asphalt cement AC with Crumb Rubber Modifier CRM is to blend and react ground CRM particles 16 mesh and finer in the AC, prior to mixing with the aggregate to produce hot mix asphalt HMA. This is known as the wet process. The dry process, where CRM is added directly to the aggregate, has historically used larger granulated CRM particles with an objective of rubberizing the aggregate. Recently, a few states have successfully tried a new concept of adding exclusively minus 80 mesh CRM directly to the aggregate. This in effect combines the dry process method with the wet process objective of modifying the AC. Adding the same CRM dry versus wet substantially lessens modification costs, but most feel the CRM reaction is very limited. The primary objective of this study was to compare the performance effects of adding the same ground CRM to HMA by the wet versus the dry process. Secondary objectives were to 1 use the SUPERPAVE binder tests to determine the effects of ground CRM in both a reacted and unreacted state and 2 determine how the gradation of ground CRM affects binder and mix properties in both processes. MM
- Civil Engineering
- Construction Equipment, Materials and Supplies