3.1 Recycling of deteriorated asphalt pavements is being used with increasing frequency for its economy and benefit of conserving raw materials. The objective of recycling is to reuse the two ingredients of asphalt concrete-aggregate and asphalt binder and to restore the desired properties to the mixture. Recycling is carried out hot or cold, depending on the condition of the deteriorated pavement, construction procedure, availability of equipment, and cost. This classification is for classifying recycling agents to be used in recycled asphalt mixtures.

Note 3: The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D3666 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Specification D3666 alone does not completely ensure reliable results. Reliable results depend on many factors; following the suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.

1.1 This standard covers a standardized method whereby recycling agents to be used in hot recycling of asphalt concrete can be classified. The recycling agents are classified by viscosity in mm²/s measured at 60 °C [140 °F]. This classification does not apply to emulsified recycling agents.

1.2 This standard does not address the performance of asphalt binder blends with recycling agents, or that of hot-mix asphalt mixture containing recycling agents. Adherence of a recycling agent to this specification does not necessarily relate to the performance of asphalt binders and mixtures containing the recycling agents.

Note 1: The impact of recycling agents has been evaluated by extracting the asphalt binder from the pavement to be recycled, and combining with the recycling agent to meet the appropriate grade within Specification D946/D946M or Table 1, 2, or 3 of Specification D3381/D3381M. More recently, some specifications have referred to performance grading as described in Specification D6373 or D8239.

Note 2: Efforts are underway to utilize performance-based testing of the asphalt mixture containing recycling agents as a measure of compliance.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.