The Influence of Time after Crushing for Cold In-Place Recycling on Compaction and Raveling

Cold in-place recycling (CIR) mills existing bound pavement with a stabilizing agent to remove all surface distresses and some structural distresses. This research investigated the influence of extending the time after crushing, aggregate type, and asphalt emulsion type on four CIR compaction metrics and on the raveling test. Aggregate was crushed in the lab to mimic the milling process of CIR and was mixed with laboratory produced asphalt emulsion at various times after crushing. Three types of aggregate were used, including one field reclaimed asphalt pavement (RAP), a limestone-based laboratory-produced RAP, and a syenite-based laboratory-produced RAP. Two types of cationic medium set (CMS) asphalt emulsions were also used: a proprietary and a commodity asphalt emulsion. One of the compaction metrics, the number of gyrations to 76% Density ( N76), was found to have the most promise for capturing the charge on the RAP, as the limestone aggregate and proprietary asphalt emulsion saw the highest resistance to compaction. These two materials were the most reactive so it was reasonable that they caused the fastest break of the asphalt emulsion. The raveling test did not produce similarly conclusive results. Whereas some trends from the raveling test showed the ability to capture charge on the RAP, perhaps the four-hour cure before the raveling test may have masked any influence of time after crushing and asphalt emulsion type.