Classification of Emulsified Recycling Agents

The use of pavement recycling has steadily gained momentum over the last ten years. This includes various methods of both hot and cold recycling. Recycling has proven to be a reliable alternative to conventional methods of rehabilitation. The end product is of high quality and may be compared to similar methods employing only virgin materials. Though the use of these methods has increased, a method of selecting and specifying recycling agents has lagged behind. ASTM now has A Standard Practice for Classifying Hot Mix Recycling Agents (D 4552-87). A similar standard for emulsified products is now being investigated. This paper presents a classification system for the selection and use of emulsified recycling agents. This classification system is derived from currently used practices and extensive field observation of the interaction between materials and methods. Terminology, methods for selection, and general use guidelines are discussed. Recycling is an important part of any pavement management system (PMS). The Federal Highway Administration has mandated the adoption of a PMS for all states. A PMS will be used to select the appropriate rehabilitation and maintenance procedure based on accepted criteria. A standard system of classification and terminology will place recycling in its proper position within the PMS. Several state DOTs have established specifications for emulsified recycling products. As needs vary, so have these specifications. States and regions have reduced the full spectrum of products to those serving local needs. The classification system will allow easier transfer of technology as the terminology is standardized. The classification system defines the emulsified recycling agents by composition as well as by intended performance. With this system in place, engineers will be able to select products on the basis of equipment on hand, traffic constraints, and intended vehicle capacity. This system may be used in application from rural roads to interstate highways.